diff --git a/CHANGELOG.md b/CHANGELOG.md
index 49291fad..8b0d31a2 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -12,6 +12,8 @@ it releases that version ([RELEASING.md](https://github.com/energy-models/mathsp
 
 ## Upcoming version
 
+- docs(pypsa): the pypsa spec names its repeated row conditions as masks, and its topic files read them under `given: masks:` ([#825](https://github.com/energy-models/mathspec/pull/825))
+- feat(language): a where predicate is named once under `masks:`, and another file reads it under `given: masks:` ([#821](https://github.com/energy-models/mathspec/pull/821))
 - feat(language)!: a construct that reads the order of a dimension needs the dimension declared ordered ([#793](https://github.com/energy-models/mathspec/pull/793))
 - docs(pypsa): the pypsa reference targets master at 51986084, where the eight rungs that diverged now match ([#844](https://github.com/energy-models/mathspec/pull/844))
 - feat(language)!: a call names the columns of a relation as relation[column], and a sum through a relation is a sum over the axes its join opens ([#664](https://github.com/energy-models/mathspec/pull/664))
diff --git a/docs/examples/pypsa.md b/docs/examples/pypsa.md
index 33aa6c9a..dedac4e2 100644
--- a/docs/examples/pypsa.md
+++ b/docs/examples/pypsa.md
@@ -5752,6 +5752,27 @@ A plain `n.optimize()`, and its multi-period and stochastic classes, in one file
 | $`\mathit{Transformer\_angle\_sum}`$ | `Transformer_angle_sum` over $`\Xi \times \mathcal{T} \times \mathcal{C}`$ |
 | $`\mathit{Cycle\_angle\_sum}`$ | `Cycle_angle_sum` over $`\Xi \times \mathcal{T} \times \mathcal{C}`$ — the voltage angle differences around a cycle: every branch flow times its cycle weight, and every transformer phase shift |
 
+#### Masks
+
+| Symbol | Meaning |
+|---|---|
+| $`\mathrm{on}^{\mathrm{com,ext}}`$ | `Generator_com_ext` over $`\mathcal{T} \times \mathcal{G}`$ — a committable generator with an extendable, non-modular build that stands in the snapshot's period — PyPSA's `com-ext` rows, whose status is relaxed against the chosen build |
+| $`\mathrm{on}^{\mathrm{mnt,ext}}`$ | `Generator_maint_ext` over $`\mathcal{T} \times \mathcal{G}`$ — a maintainable generator with an extendable build, unless it is committable and modular, that stands in the snapshot's period — the maintenance rows against the chosen build |
+| $`\mathrm{on}^{\mathrm{com}}`$ | `Generator_committed` over $`\mathcal{T} \times \mathcal{G}`$ — a committable generator that stands in the snapshot's period — every unit-commitment row's set |
+| $`\mathrm{prev}`$ | `Generator_ramps_from_previous` over $`\Xi \times \mathcal{T} \times \mathcal{G}`$ — a snapshot whose ramp reads a previous output — any snapshot but its period's first, and the horizon's first where the generator comes in off or carries an initial output |
+| $`\mathrm{on}^{f,\mathrm{com,ext}}`$ | `Link_com_ext` over $`\mathcal{T} \times \mathcal{L}`$ — a committable link with an extendable, non-modular build that stands in the snapshot's period — PyPSA's `com-ext` rows, whose status is relaxed against the chosen build |
+| $`\mathrm{on}^{f,\mathrm{mnt,ext}}`$ | `Link_maint_ext` over $`\mathcal{T} \times \mathcal{L}`$ — a maintainable link with an extendable build, unless it is committable and modular, that stands in the snapshot's period — the maintenance rows against the chosen build |
+| $`\mathrm{on}^{f,\mathrm{com}}`$ | `Link_committed` over $`\mathcal{T} \times \mathcal{L}`$ — a committable link that stands in the snapshot's period — every unit-commitment row's set |
+| $`\mathrm{prev}^{f}`$ | `Link_ramps_from_previous` over $`\Xi \times \mathcal{T} \times \mathcal{L}`$ — a snapshot whose ramp reads a previous output — any snapshot but its period's first, and the horizon's first where the link comes in off or carries an initial output |
+| $`\mathrm{on}^{z,\mathrm{com,ext}}`$ | `Process_com_ext` over $`\mathcal{T} \times \mathcal{J}`$ — a committable process with an extendable, non-modular build that stands in the snapshot's period — PyPSA's `com-ext` rows, whose status is relaxed against the chosen build |
+| $`\mathrm{on}^{z,\mathrm{mnt,ext}}`$ | `Process_maint_ext` over $`\mathcal{T} \times \mathcal{J}`$ — a maintainable process with an extendable build, unless it is committable and modular, that stands in the snapshot's period — the maintenance rows against the chosen build |
+| $`\mathrm{on}^{z,\mathrm{com}}`$ | `Process_committed` over $`\mathcal{T} \times \mathcal{J}`$ — a committable process that stands in the snapshot's period — every unit-commitment row's set |
+| $`\mathrm{prev}^{z}`$ | `Process_ramps_from_previous` over $`\Xi \times \mathcal{T} \times \mathcal{J}`$ — a snapshot whose ramp reads a previous output — any snapshot but its period's first, and the horizon's first where the process comes in off or carries an initial output |
+| $`\mathrm{on}^{h,\mathrm{fix}}`$ | `StorageUnit_fix` over $`\mathcal{T} \times \mathcal{S}`$ — a storage unit with a fixed build that stands in the snapshot's period — PyPSA's `fix` rows |
+| $`\mathrm{on}^{h,\mathrm{ext}}`$ | `StorageUnit_ext` over $`\mathcal{T} \times \mathcal{S}`$ — a storage unit with an extendable build that stands in the snapshot's period — PyPSA's `ext` rows |
+| $`\mathrm{on}^{s,\mathrm{lossy}}`$ | `Line_lossy` over $`\mathcal{T} \times \mathcal{K}`$ — a line that stands in the snapshot's period, where the run models transmission losses |
+| $`\mathrm{on}^{\sigma,\mathrm{lossy}}`$ | `Transformer_lossy` over $`\mathcal{T} \times \mathcal{M}`$ — a transformer that stands in the snapshot's period, where the run models transmission losses |
+
 Upright is what the data supplies — a parameter such as $`\mathrm{Transformer\_phase\_shift\_varying}`$, a coordinate map, a label — and italic is what the solver chooses, such as $`\mathit{Transformer\_phase\_shift}`$. An index is italic too, being what a quantifier chooses, and a set is script.
 
 $`t \ominus k`$ denotes cyclic translation: index $`t-k`$ taken modulo the size of the dimension (`roll`). Plain $`t-k`$ (`shift`) has no wraparound — terms translated past the edge are simply absent.
@@ -6154,12 +6175,12 @@ Z_{j} = \mathrm{z}^{\mathrm{nom,set}}_{j} \qquad \forall\, j \in \mathcal{J} \,:
 StorageUnit_fix_p_dispatch_lower:
   description: "`StorageUnit-fix-p_dispatch-lower` — dispatch is non-negative"
   dims: [scenario, snapshot, storage_unit]
-  where: not StorageUnit_p_nom_extendable AND StorageUnit_active
+  where: StorageUnit_fix
   expression: StorageUnit_p_dispatch >= 0
 ```
 
 ```math
-h^{+}_{\xi,t,s} \ge 0 \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ s \in \mathcal{S} \,:\, \neg \mathrm{ext}^{h}_{s} \wedge \mathrm{on}^{h}_{t,s}
+h^{+}_{\xi,t,s} \ge 0 \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ s \in \mathcal{S} \,:\, \mathrm{on}^{h,\mathrm{fix}}_{t,s}
 ```
 
 ### `StorageUnit-fix-p_dispatch-upper`
@@ -6170,12 +6191,12 @@ h^{+}_{\xi,t,s} \ge 0 \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ s \in \
 StorageUnit_fix_p_dispatch_upper:
   description: "`StorageUnit-fix-p_dispatch-upper` — a fixed unit dispatches at most its nominal power"
   dims: [scenario, snapshot, storage_unit]
-  where: not StorageUnit_p_nom_extendable AND StorageUnit_active
+  where: StorageUnit_fix
   expression: StorageUnit_p_dispatch <= StorageUnit_p_max_pu * StorageUnit_p_nom
 ```
 
 ```math
-h^{+}_{\xi,t,s} \le \overline{\mathrm{h}}_{\xi,t,s} \cdot \mathrm{h}^{\mathrm{nom}}_{\xi,s} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ s \in \mathcal{S} \,:\, \neg \mathrm{ext}^{h}_{s} \wedge \mathrm{on}^{h}_{t,s}
+h^{+}_{\xi,t,s} \le \overline{\mathrm{h}}_{\xi,t,s} \cdot \mathrm{h}^{\mathrm{nom}}_{\xi,s} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ s \in \mathcal{S} \,:\, \mathrm{on}^{h,\mathrm{fix}}_{t,s}
 ```
 
 ### `StorageUnit-fix-p_store-lower`
@@ -6186,12 +6207,12 @@ h^{+}_{\xi,t,s} \le \overline{\mathrm{h}}_{\xi,t,s} \cdot \mathrm{h}^{\mathrm{no
 StorageUnit_fix_p_store_lower:
   description: "`StorageUnit-fix-p_store-lower` — storing is non-negative"
   dims: [scenario, snapshot, storage_unit]
-  where: not StorageUnit_p_nom_extendable AND StorageUnit_active
+  where: StorageUnit_fix
   expression: StorageUnit_p_store >= 0
 ```
 
 ```math
-h^{-}_{\xi,t,s} \ge 0 \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ s \in \mathcal{S} \,:\, \neg \mathrm{ext}^{h}_{s} \wedge \mathrm{on}^{h}_{t,s}
+h^{-}_{\xi,t,s} \ge 0 \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ s \in \mathcal{S} \,:\, \mathrm{on}^{h,\mathrm{fix}}_{t,s}
 ```
 
 ### `StorageUnit-fix-p_store-upper`
@@ -6204,12 +6225,12 @@ StorageUnit_fix_p_store_upper:
     `StorageUnit-fix-p_store-upper` — a fixed unit stores at most its
     nominal power, the minimum-per-unit column carrying that cap negated
   dims: [scenario, snapshot, storage_unit]
-  where: not StorageUnit_p_nom_extendable AND StorageUnit_active
+  where: StorageUnit_fix
   expression: StorageUnit_p_store <= -StorageUnit_p_min_pu * StorageUnit_p_nom
 ```
 
 ```math
-h^{-}_{\xi,t,s} \le -\underline{\mathrm{h}}_{\xi,t,s} \cdot \mathrm{h}^{\mathrm{nom}}_{\xi,s} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ s \in \mathcal{S} \,:\, \neg \mathrm{ext}^{h}_{s} \wedge \mathrm{on}^{h}_{t,s}
+h^{-}_{\xi,t,s} \le -\underline{\mathrm{h}}_{\xi,t,s} \cdot \mathrm{h}^{\mathrm{nom}}_{\xi,s} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ s \in \mathcal{S} \,:\, \mathrm{on}^{h,\mathrm{fix}}_{t,s}
 ```
 
 ### `StorageUnit-fix-state_of_charge-lower`
@@ -6220,12 +6241,12 @@ h^{-}_{\xi,t,s} \le -\underline{\mathrm{h}}_{\xi,t,s} \cdot \mathrm{h}^{\mathrm{
 StorageUnit_fix_state_of_charge_lower:
   description: "`StorageUnit-fix-state_of_charge-lower` — charge is non-negative"
   dims: [scenario, snapshot, storage_unit]
-  where: not StorageUnit_p_nom_extendable AND StorageUnit_active
+  where: StorageUnit_fix
   expression: StorageUnit_state_of_charge >= 0
 ```
 
 ```math
-\mathit{soc}_{\xi,t,s} \ge 0 \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ s \in \mathcal{S} \,:\, \neg \mathrm{ext}^{h}_{s} \wedge \mathrm{on}^{h}_{t,s}
+\mathit{soc}_{\xi,t,s} \ge 0 \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ s \in \mathcal{S} \,:\, \mathrm{on}^{h,\mathrm{fix}}_{t,s}
 ```
 
 ### `StorageUnit-fix-state_of_charge-upper`
@@ -6236,12 +6257,12 @@ StorageUnit_fix_state_of_charge_lower:
 StorageUnit_fix_state_of_charge_upper:
   description: "`StorageUnit-fix-state_of_charge-upper` — a fixed unit holds at most its hours at nominal power"
   dims: [scenario, snapshot, storage_unit]
-  where: not StorageUnit_p_nom_extendable AND StorageUnit_active
+  where: StorageUnit_fix
   expression: StorageUnit_state_of_charge <= StorageUnit_max_hours * StorageUnit_p_nom
 ```
 
 ```math
-\mathit{soc}_{\xi,t,s} \le \mathrm{T}^{h}_{\xi,s} \cdot \mathrm{h}^{\mathrm{nom}}_{\xi,s} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ s \in \mathcal{S} \,:\, \neg \mathrm{ext}^{h}_{s} \wedge \mathrm{on}^{h}_{t,s}
+\mathit{soc}_{\xi,t,s} \le \mathrm{T}^{h}_{\xi,s} \cdot \mathrm{h}^{\mathrm{nom}}_{\xi,s} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ s \in \mathcal{S} \,:\, \mathrm{on}^{h,\mathrm{fix}}_{t,s}
 ```
 
 ### `Generator-com-p-lower`
@@ -6252,12 +6273,12 @@ StorageUnit_fix_state_of_charge_upper:
 Generator_com_p_lower:
   description: "`Generator-com-p-lower` — a committed unit outputs at least its minimum; off, at least nothing"
   dims: [scenario, snapshot, generator]
-  where: Generator_committable AND not Generator_p_nom_extendable AND NOT (Generator_p_nom_mod > 0) AND Generator_active
+  where: Generator_committed AND NOT Generator_p_nom_extendable AND NOT (Generator_p_nom_mod > 0)
   expression: Generator_p >= Generator_p_min_pu * Generator_p_nom * (Generator_status - Generator_maintenance_pu * Generator_maintenance_status)
 ```
 
 ```math
-p_{\xi,t,g} \ge \underline{\mathrm{p}}_{\xi,t,g} \cdot \mathrm{p}^{\mathrm{nom}}_{\xi,g} \cdot \left( u_{\xi,t,g} - \gamma_{\xi,g} \cdot \mu^{u}_{\xi,t,g} \right) \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{com}_{g} \wedge \neg \mathrm{ext}_{g} \wedge \neg \left( \mathrm{p}^{\mathrm{mod}}_{g} > 0 \right) \wedge \mathrm{on}_{t,g}
+p_{\xi,t,g} \ge \underline{\mathrm{p}}_{\xi,t,g} \cdot \mathrm{p}^{\mathrm{nom}}_{\xi,g} \cdot \left( u_{\xi,t,g} - \gamma_{\xi,g} \cdot \mu^{u}_{\xi,t,g} \right) \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{on}^{\mathrm{com}}_{t,g} \wedge \neg \mathrm{ext}_{g} \wedge \neg \left( \mathrm{p}^{\mathrm{mod}}_{g} > 0 \right)
 ```
 
 ### `Generator-com-p-upper`
@@ -6268,12 +6289,12 @@ p_{\xi,t,g} \ge \underline{\mathrm{p}}_{\xi,t,g} \cdot \mathrm{p}^{\mathrm{nom}}
 Generator_com_p_upper:
   description: "`Generator-com-p-upper` — a committed unit outputs at most what is available; off, at most nothing"
   dims: [scenario, snapshot, generator]
-  where: Generator_committable AND not Generator_p_nom_extendable AND NOT (Generator_p_nom_mod > 0) AND Generator_active
+  where: Generator_committed AND NOT Generator_p_nom_extendable AND NOT (Generator_p_nom_mod > 0)
   expression: Generator_p <= Generator_p_max_pu * Generator_p_nom * (Generator_status - Generator_maintenance_pu * Generator_maintenance_status)
 ```
 
 ```math
-p_{\xi,t,g} \le \overline{\mathrm{p}}_{\xi,t,g} \cdot \mathrm{p}^{\mathrm{nom}}_{\xi,g} \cdot \left( u_{\xi,t,g} - \gamma_{\xi,g} \cdot \mu^{u}_{\xi,t,g} \right) \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{com}_{g} \wedge \neg \mathrm{ext}_{g} \wedge \neg \left( \mathrm{p}^{\mathrm{mod}}_{g} > 0 \right) \wedge \mathrm{on}_{t,g}
+p_{\xi,t,g} \le \overline{\mathrm{p}}_{\xi,t,g} \cdot \mathrm{p}^{\mathrm{nom}}_{\xi,g} \cdot \left( u_{\xi,t,g} - \gamma_{\xi,g} \cdot \mu^{u}_{\xi,t,g} \right) \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{on}^{\mathrm{com}}_{t,g} \wedge \neg \mathrm{ext}_{g} \wedge \neg \left( \mathrm{p}^{\mathrm{mod}}_{g} > 0 \right)
 ```
 
 ### `Generator-com-transition-start-up`
@@ -6284,12 +6305,12 @@ p_{\xi,t,g} \le \overline{\mathrm{p}}_{\xi,t,g} \cdot \mathrm{p}^{\mathrm{nom}}_
 Generator_com_transition_start_up:
   description: "`Generator-com-transition-start-up` — turning on is a start, counted against the state the unit carried into the snapshot"
   dims: [scenario, snapshot, generator]
-  where: Generator_committable AND Generator_active
+  where: Generator_committed
   expression: Generator_start_up >= Generator_status - Generator_previous_status
 ```
 
 ```math
-\mathit{up}_{\xi,t,g} \ge u_{\xi,t,g} - \overleftarrow{u}_{\xi,t,g} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{com}_{g} \wedge \mathrm{on}_{t,g}
+\mathit{up}_{\xi,t,g} \ge u_{\xi,t,g} - \overleftarrow{u}_{\xi,t,g} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{on}^{\mathrm{com}}_{t,g}
 ```
 
 ### `Generator-com-transition-shut-down`
@@ -6300,12 +6321,12 @@ Generator_com_transition_start_up:
 Generator_com_transition_shut_down:
   description: "`Generator-com-transition-shut-down` — turning off is a stop, counted against the state the unit carried into the snapshot"
   dims: [scenario, snapshot, generator]
-  where: Generator_committable AND Generator_active
+  where: Generator_committed
   expression: Generator_shut_down >= Generator_previous_status - Generator_status
 ```
 
 ```math
-\mathit{dn}_{\xi,t,g} \ge \overleftarrow{u}_{\xi,t,g} - u_{\xi,t,g} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{com}_{g} \wedge \mathrm{on}_{t,g}
+\mathit{dn}_{\xi,t,g} \ge \overleftarrow{u}_{\xi,t,g} - u_{\xi,t,g} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{on}^{\mathrm{com}}_{t,g}
 ```
 
 ### `Generator-com-up-time`
@@ -6319,12 +6340,12 @@ Generator_com_up_time:
     is still on. The first snapshot's share of the window is the brought-in
     up time's, which the must-stay-up mask carries
   dims: [scenario, snapshot, generator]
-  where: Generator_committable AND Generator_min_up_time > 0 AND position(snapshot) > 0 AND Generator_active
+  where: Generator_committed AND Generator_min_up_time > 0 AND position(snapshot) > 0
   expression: sum_back(Generator_start_up, along=snapshot, window=Generator_min_up_time) <= Generator_status
 ```
 
 ```math
-\sum_{t' \in \mathcal{T} \,:\, 0 \le t - t' < \mathrm{UT}} \mathit{up}_{\xi,t',g} \le u_{\xi,t,g} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{com}_{g} \wedge \mathrm{UT}_{\xi,g} > 0 \wedge \mathrm{pos}(t) > 0 \wedge \mathrm{on}_{t,g}
+\sum_{t' \in \mathcal{T} \,:\, 0 \le t - t' < \mathrm{UT}} \mathit{up}_{\xi,t',g} \le u_{\xi,t,g} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{on}^{\mathrm{com}}_{t,g} \wedge \mathrm{UT}_{\xi,g} > 0 \wedge \mathrm{pos}(t) > 0
 ```
 
 ### `Generator-com-down-time`
@@ -6338,12 +6359,12 @@ Generator_com_down_time:
     time is still off. The first snapshot's share of the window is the
     brought-in down time's, which the must-stay-down mask carries
   dims: [scenario, snapshot, generator]
-  where: Generator_committable AND Generator_min_down_time > 0 AND position(snapshot) > 0 AND Generator_active
+  where: Generator_committed AND Generator_min_down_time > 0 AND position(snapshot) > 0
   expression: sum_back(Generator_shut_down, along=snapshot, window=Generator_min_down_time) <= 1 - Generator_status
 ```
 
 ```math
-\sum_{t' \in \mathcal{T} \,:\, 0 \le t - t' < \mathrm{DT}} \mathit{dn}_{\xi,t',g} \le 1 - u_{\xi,t,g} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{com}_{g} \wedge \mathrm{DT}_{\xi,g} > 0 \wedge \mathrm{pos}(t) > 0 \wedge \mathrm{on}_{t,g}
+\sum_{t' \in \mathcal{T} \,:\, 0 \le t - t' < \mathrm{DT}} \mathit{dn}_{\xi,t',g} \le 1 - u_{\xi,t,g} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{on}^{\mathrm{com}}_{t,g} \wedge \mathrm{DT}_{\xi,g} > 0 \wedge \mathrm{pos}(t) > 0
 ```
 
 ### `Generator-com-status-min_up_time_must_stay_up`
@@ -6354,12 +6375,12 @@ Generator_com_down_time:
 Generator_com_status_must_stay_up:
   description: "`Generator-com-status-min_up_time_must_stay_up` — a unit still serving the up time it brought in stays on"
   dims: [scenario, snapshot, generator]
-  where: Generator_committable AND Generator_must_stay_up AND Generator_active
+  where: Generator_committed AND Generator_must_stay_up
   expression: Generator_status == 1
 ```
 
 ```math
-u_{\xi,t,g} = 1 \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{com}_{g} \wedge \mathrm{hold}_{\xi,t,g} \wedge \mathrm{on}_{t,g}
+u_{\xi,t,g} = 1 \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{on}^{\mathrm{com}}_{t,g} \wedge \mathrm{hold}_{\xi,t,g}
 ```
 
 ### `Generator-com-status-min_down_time_must_stay_up`
@@ -6372,12 +6393,12 @@ Generator_com_status_must_stay_down:
     `Generator-com-status-min_down_time_must_stay_up` — a unit still serving
     the down time it brought in stays off; PyPSA names the row `_must_stay_up`
   dims: [scenario, snapshot, generator]
-  where: Generator_committable AND Generator_must_stay_down AND Generator_active
+  where: Generator_committed AND Generator_must_stay_down
   expression: Generator_status == 0
 ```
 
 ```math
-u_{\xi,t,g} = 0 \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{com}_{g} \wedge \mathrm{rest}_{\xi,t,g} \wedge \mathrm{on}_{t,g}
+u_{\xi,t,g} = 0 \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{on}^{\mathrm{com}}_{t,g} \wedge \mathrm{rest}_{\xi,t,g}
 ```
 
 ### `Generator-p-ramp_limit_up-run-bigM`
@@ -6392,10 +6413,9 @@ Generator_p_ramp_limit_up_run_big_m:
     releases the row in the snapshot it turns on
   dims: [scenario, snapshot, generator]
   where: >-
-    Generator_committable AND Generator_p_nom_extendable AND NOT (Generator_p_nom_mod > 0)
+    Generator_com_ext
     AND (Generator_ramp_limit_up OR Generator_ramp_limit_start_up)
-    AND (position(snapshot, within=snapshot_period[period]) > 0 OR (position(snapshot) == 0 AND (Generator_status_initial == 0 OR Generator_p_init)))
-    AND Generator_active
+    AND Generator_ramps_from_previous
   expression: >-
     Generator_p - Generator_previous_p <=
     Generator_ramp_up_rate * Generator_p_nom_ext
@@ -6403,7 +6423,7 @@ Generator_p_ramp_limit_up_run_big_m:
 ```
 
 ```math
-p_{\xi,t,g} - \overleftarrow{p}_{\xi,t,g} \le \widetilde{\mathrm{ru}}_{\xi,t,g} \cdot P_{g} + \mathrm{M}_{\xi,g} - \mathrm{M}_{\xi,g} \cdot \overleftarrow{u}_{\xi,t,g} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{com}_{g} \wedge \mathrm{ext}_{g} \wedge \neg \left( \mathrm{p}^{\mathrm{mod}}_{g} > 0 \right) \wedge \left( \mathrm{ru}_{\xi,t,g} \text{ is defined} \vee \mathrm{ru}^{\mathrm{up}}_{\xi,g} \text{ is defined} \right) \wedge \left( \mathrm{pos}_{\mathrm{snapshot\_period}(t)}(t) > 0 \vee \mathrm{pos}(t) = 0 \wedge \left( \mathrm{u}^{0}_{\xi,g} = 0 \vee \mathrm{p}^{0}_{\xi,g} \text{ is defined} \right) \right) \wedge \mathrm{on}_{t,g}
+p_{\xi,t,g} - \overleftarrow{p}_{\xi,t,g} \le \widetilde{\mathrm{ru}}_{\xi,t,g} \cdot P_{g} + \mathrm{M}_{\xi,g} - \mathrm{M}_{\xi,g} \cdot \overleftarrow{u}_{\xi,t,g} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{on}^{\mathrm{com,ext}}_{t,g} \wedge \left( \mathrm{ru}_{\xi,t,g} \text{ is defined} \vee \mathrm{ru}^{\mathrm{up}}_{\xi,g} \text{ is defined} \right) \wedge \mathrm{prev}_{\xi,t,g}
 ```
 
 ### `Generator-p-ramp_limit_up-start-bigM`
@@ -6418,10 +6438,9 @@ Generator_p_ramp_limit_up_start_big_m:
     the chosen build; the big M releases the row everywhere else
   dims: [scenario, snapshot, generator]
   where: >-
-    Generator_committable AND Generator_p_nom_extendable AND NOT (Generator_p_nom_mod > 0)
+    Generator_com_ext
     AND (Generator_ramp_limit_up OR Generator_ramp_limit_start_up)
-    AND (position(snapshot, within=snapshot_period[period]) > 0 OR (position(snapshot) == 0 AND (Generator_status_initial == 0 OR Generator_p_init)))
-    AND Generator_active
+    AND Generator_ramps_from_previous
   expression: >-
     Generator_p - Generator_previous_p <=
     Generator_start_up_rate * Generator_p_nom_ext
@@ -6429,7 +6448,7 @@ Generator_p_ramp_limit_up_start_big_m:
 ```
 
 ```math
-p_{\xi,t,g} - \overleftarrow{p}_{\xi,t,g} \le \widetilde{\mathrm{ru}}^{\mathrm{up}}_{\xi,g} \cdot P_{g} + \mathrm{M}_{\xi,g} - \mathrm{M}_{\xi,g} \cdot \mathit{up}_{\xi,t,g} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{com}_{g} \wedge \mathrm{ext}_{g} \wedge \neg \left( \mathrm{p}^{\mathrm{mod}}_{g} > 0 \right) \wedge \left( \mathrm{ru}_{\xi,t,g} \text{ is defined} \vee \mathrm{ru}^{\mathrm{up}}_{\xi,g} \text{ is defined} \right) \wedge \left( \mathrm{pos}_{\mathrm{snapshot\_period}(t)}(t) > 0 \vee \mathrm{pos}(t) = 0 \wedge \left( \mathrm{u}^{0}_{\xi,g} = 0 \vee \mathrm{p}^{0}_{\xi,g} \text{ is defined} \right) \right) \wedge \mathrm{on}_{t,g}
+p_{\xi,t,g} - \overleftarrow{p}_{\xi,t,g} \le \widetilde{\mathrm{ru}}^{\mathrm{up}}_{\xi,g} \cdot P_{g} + \mathrm{M}_{\xi,g} - \mathrm{M}_{\xi,g} \cdot \mathit{up}_{\xi,t,g} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{on}^{\mathrm{com,ext}}_{t,g} \wedge \left( \mathrm{ru}_{\xi,t,g} \text{ is defined} \vee \mathrm{ru}^{\mathrm{up}}_{\xi,g} \text{ is defined} \right) \wedge \mathrm{prev}_{\xi,t,g}
 ```
 
 ### `Generator-p-ramp_limit_down-run-bigM`
@@ -6444,10 +6463,9 @@ Generator_p_ramp_limit_down_run_big_m:
     releases the row in the snapshot it turns off
   dims: [scenario, snapshot, generator]
   where: >-
-    Generator_committable AND Generator_p_nom_extendable AND NOT (Generator_p_nom_mod > 0)
+    Generator_com_ext
     AND (Generator_ramp_limit_down OR Generator_ramp_limit_shut_down)
-    AND (position(snapshot, within=snapshot_period[period]) > 0 OR (position(snapshot) == 0 AND (Generator_status_initial == 0 OR Generator_p_init)))
-    AND Generator_active
+    AND Generator_ramps_from_previous
   expression: >-
     Generator_previous_p - Generator_p <=
     Generator_ramp_down_rate * Generator_p_nom_ext
@@ -6455,7 +6473,7 @@ Generator_p_ramp_limit_down_run_big_m:
 ```
 
 ```math
-\overleftarrow{p}_{\xi,t,g} - p_{\xi,t,g} \le \widetilde{\mathrm{rd}}_{\xi,t,g} \cdot P_{g} + \mathrm{M}_{\xi,g} - \mathrm{M}_{\xi,g} \cdot u_{\xi,t,g} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{com}_{g} \wedge \mathrm{ext}_{g} \wedge \neg \left( \mathrm{p}^{\mathrm{mod}}_{g} > 0 \right) \wedge \left( \mathrm{rd}_{\xi,t,g} \text{ is defined} \vee \mathrm{rd}^{\mathrm{dn}}_{\xi,g} \text{ is defined} \right) \wedge \left( \mathrm{pos}_{\mathrm{snapshot\_period}(t)}(t) > 0 \vee \mathrm{pos}(t) = 0 \wedge \left( \mathrm{u}^{0}_{\xi,g} = 0 \vee \mathrm{p}^{0}_{\xi,g} \text{ is defined} \right) \right) \wedge \mathrm{on}_{t,g}
+\overleftarrow{p}_{\xi,t,g} - p_{\xi,t,g} \le \widetilde{\mathrm{rd}}_{\xi,t,g} \cdot P_{g} + \mathrm{M}_{\xi,g} - \mathrm{M}_{\xi,g} \cdot u_{\xi,t,g} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{on}^{\mathrm{com,ext}}_{t,g} \wedge \left( \mathrm{rd}_{\xi,t,g} \text{ is defined} \vee \mathrm{rd}^{\mathrm{dn}}_{\xi,g} \text{ is defined} \right) \wedge \mathrm{prev}_{\xi,t,g}
 ```
 
 ### `Generator-p-ramp_limit_down-shut-bigM`
@@ -6470,10 +6488,9 @@ Generator_p_ramp_limit_down_shut_big_m:
     the chosen build; the big M releases the row everywhere else
   dims: [scenario, snapshot, generator]
   where: >-
-    Generator_committable AND Generator_p_nom_extendable AND NOT (Generator_p_nom_mod > 0)
+    Generator_com_ext
     AND (Generator_ramp_limit_down OR Generator_ramp_limit_shut_down)
-    AND (position(snapshot, within=snapshot_period[period]) > 0 OR (position(snapshot) == 0 AND (Generator_status_initial == 0 OR Generator_p_init)))
-    AND Generator_active
+    AND Generator_ramps_from_previous
   expression: >-
     Generator_previous_p - Generator_p <=
     Generator_shut_down_rate * Generator_p_nom_ext
@@ -6481,7 +6498,7 @@ Generator_p_ramp_limit_down_shut_big_m:
 ```
 
 ```math
-\overleftarrow{p}_{\xi,t,g} - p_{\xi,t,g} \le \widetilde{\mathrm{rd}}^{\mathrm{dn}}_{\xi,g} \cdot P_{g} + \mathrm{M}_{\xi,g} - \mathrm{M}_{\xi,g} \cdot \mathit{dn}_{\xi,t,g} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{com}_{g} \wedge \mathrm{ext}_{g} \wedge \neg \left( \mathrm{p}^{\mathrm{mod}}_{g} > 0 \right) \wedge \left( \mathrm{rd}_{\xi,t,g} \text{ is defined} \vee \mathrm{rd}^{\mathrm{dn}}_{\xi,g} \text{ is defined} \right) \wedge \left( \mathrm{pos}_{\mathrm{snapshot\_period}(t)}(t) > 0 \vee \mathrm{pos}(t) = 0 \wedge \left( \mathrm{u}^{0}_{\xi,g} = 0 \vee \mathrm{p}^{0}_{\xi,g} \text{ is defined} \right) \right) \wedge \mathrm{on}_{t,g}
+\overleftarrow{p}_{\xi,t,g} - p_{\xi,t,g} \le \widetilde{\mathrm{rd}}^{\mathrm{dn}}_{\xi,g} \cdot P_{g} + \mathrm{M}_{\xi,g} - \mathrm{M}_{\xi,g} \cdot \mathit{dn}_{\xi,t,g} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{on}^{\mathrm{com,ext}}_{t,g} \wedge \left( \mathrm{rd}_{\xi,t,g} \text{ is defined} \vee \mathrm{rd}^{\mathrm{dn}}_{\xi,g} \text{ is defined} \right) \wedge \mathrm{prev}_{\xi,t,g}
 ```
 
 ### `Generator-p_nom_modularity`
@@ -6510,12 +6527,12 @@ Generator_com_ext_p_upper_cap:
     `Generator-com-ext-p-upper-cap` — a committed extendable unit outputs
     at most what is available of the chosen build, whatever its status
   dims: [scenario, snapshot, generator]
-  where: Generator_committable AND Generator_p_nom_extendable AND NOT (Generator_p_nom_mod > 0) AND Generator_active
+  where: Generator_com_ext
   expression: Generator_p <= Generator_p_max_pu * (Generator_p_nom_ext - Generator_maintenance_pu * Generator_maintenance_capacity)
 ```
 
 ```math
-p_{\xi,t,g} \le \overline{\mathrm{p}}_{\xi,t,g} \cdot \left( P_{g} - \gamma_{\xi,g} \cdot \mu^{\mathrm{nom}}_{\xi,t,g} \right) \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{com}_{g} \wedge \mathrm{ext}_{g} \wedge \neg \left( \mathrm{p}^{\mathrm{mod}}_{g} > 0 \right) \wedge \mathrm{on}_{t,g}
+p_{\xi,t,g} \le \overline{\mathrm{p}}_{\xi,t,g} \cdot \left( P_{g} - \gamma_{\xi,g} \cdot \mu^{\mathrm{nom}}_{\xi,t,g} \right) \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{on}^{\mathrm{com,ext}}_{t,g}
 ```
 
 ### `Generator-com-ext-p-upper-bigM`
@@ -6526,12 +6543,12 @@ p_{\xi,t,g} \le \overline{\mathrm{p}}_{\xi,t,g} \cdot \left( P_{g} - \gamma_{\xi
 Generator_com_ext_p_upper_big_m:
   description: "`Generator-com-ext-p-upper-bigM` — off, a unit outputs nothing; on, the big M is no bound"
   dims: [scenario, snapshot, generator]
-  where: Generator_committable AND Generator_p_nom_extendable AND NOT (Generator_p_nom_mod > 0) AND Generator_active
+  where: Generator_com_ext
   expression: Generator_p <= Generator_big_m * Generator_status
 ```
 
 ```math
-p_{\xi,t,g} \le \mathrm{M}_{\xi,g} \cdot u_{\xi,t,g} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{com}_{g} \wedge \mathrm{ext}_{g} \wedge \neg \left( \mathrm{p}^{\mathrm{mod}}_{g} > 0 \right) \wedge \mathrm{on}_{t,g}
+p_{\xi,t,g} \le \mathrm{M}_{\xi,g} \cdot u_{\xi,t,g} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{on}^{\mathrm{com,ext}}_{t,g}
 ```
 
 ### `Generator-com-ext-p-lower`
@@ -6544,7 +6561,7 @@ Generator_com_ext_p_lower:
     `Generator-com-ext-p-lower` — a committed extendable unit outputs at
     least its minimum of the chosen build; off, the big M releases the row
   dims: [scenario, snapshot, generator]
-  where: Generator_committable AND Generator_p_nom_extendable AND NOT (Generator_p_nom_mod > 0) AND Generator_active
+  where: Generator_com_ext
   expression: >-
     Generator_p >=
     Generator_p_min_pu * (Generator_p_nom_ext - Generator_maintenance_pu * Generator_maintenance_capacity)
@@ -6552,7 +6569,7 @@ Generator_com_ext_p_lower:
 ```
 
 ```math
-p_{\xi,t,g} \ge \underline{\mathrm{p}}_{\xi,t,g} \cdot \left( P_{g} - \gamma_{\xi,g} \cdot \mu^{\mathrm{nom}}_{\xi,t,g} \right) + \mathrm{M}_{\xi,g} \cdot u_{\xi,t,g} - \mathrm{M}_{\xi,g} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{com}_{g} \wedge \mathrm{ext}_{g} \wedge \neg \left( \mathrm{p}^{\mathrm{mod}}_{g} > 0 \right) \wedge \mathrm{on}_{t,g}
+p_{\xi,t,g} \ge \underline{\mathrm{p}}_{\xi,t,g} \cdot \left( P_{g} - \gamma_{\xi,g} \cdot \mu^{\mathrm{nom}}_{\xi,t,g} \right) + \mathrm{M}_{\xi,g} \cdot u_{\xi,t,g} - \mathrm{M}_{\xi,g} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{on}^{\mathrm{com,ext}}_{t,g}
 ```
 
 ### `Generator-com-ext-p-lower-nonneg`
@@ -6566,14 +6583,12 @@ Generator_com_ext_p_lower_nonneg:
     negative, output is also plainly non-negative, a row the big-M lower
     cannot assert while the unit is off
   dims: [scenario, snapshot, generator]
-  where: >-
-    Generator_committable AND Generator_p_nom_extendable
-    AND Generator_p_min_pu_nonneg AND NOT (Generator_p_nom_mod > 0) AND Generator_active
+  where: Generator_com_ext AND Generator_p_min_pu_nonneg
   expression: Generator_p >= 0
 ```
 
 ```math
-p_{\xi,t,g} \ge 0 \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{com}_{g} \wedge \mathrm{ext}_{g} \wedge \mathrm{nonneg}_{g} \wedge \neg \left( \mathrm{p}^{\mathrm{mod}}_{g} > 0 \right) \wedge \mathrm{on}_{t,g}
+p_{\xi,t,g} \ge 0 \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{on}^{\mathrm{com,ext}}_{t,g} \wedge \mathrm{nonneg}_{g}
 ```
 
 ### `Generator-com-mod-p-lower`
@@ -6586,12 +6601,12 @@ Generator_com_mod_p_lower:
     `Generator-com-mod-p-lower` — a committed modular unit outputs at least
     its minimum of one module, whether the build is fixed or a decision
   dims: [scenario, snapshot, generator]
-  where: Generator_committable AND Generator_p_nom_mod > 0 AND Generator_active
+  where: Generator_committed AND Generator_p_nom_mod > 0
   expression: Generator_p >= Generator_p_min_pu * Generator_p_nom_mod * (Generator_status - Generator_maintenance_pu * Generator_maintenance_status)
 ```
 
 ```math
-p_{\xi,t,g} \ge \underline{\mathrm{p}}_{\xi,t,g} \cdot \mathrm{p}^{\mathrm{mod}}_{g} \cdot \left( u_{\xi,t,g} - \gamma_{\xi,g} \cdot \mu^{u}_{\xi,t,g} \right) \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{com}_{g} \wedge \mathrm{p}^{\mathrm{mod}}_{g} > 0 \wedge \mathrm{on}_{t,g}
+p_{\xi,t,g} \ge \underline{\mathrm{p}}_{\xi,t,g} \cdot \mathrm{p}^{\mathrm{mod}}_{g} \cdot \left( u_{\xi,t,g} - \gamma_{\xi,g} \cdot \mu^{u}_{\xi,t,g} \right) \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{on}^{\mathrm{com}}_{t,g} \wedge \mathrm{p}^{\mathrm{mod}}_{g} > 0
 ```
 
 ### `Generator-com-mod-p-upper`
@@ -6604,12 +6619,12 @@ Generator_com_mod_p_upper:
     `Generator-com-mod-p-upper` — a committed modular unit outputs at most
     one module's share, whether the build is fixed or a decision
   dims: [scenario, snapshot, generator]
-  where: Generator_committable AND Generator_p_nom_mod > 0 AND Generator_active
+  where: Generator_committed AND Generator_p_nom_mod > 0
   expression: Generator_p <= Generator_p_max_pu * Generator_p_nom_mod * (Generator_status - Generator_maintenance_pu * Generator_maintenance_status)
 ```
 
 ```math
-p_{\xi,t,g} \le \overline{\mathrm{p}}_{\xi,t,g} \cdot \mathrm{p}^{\mathrm{mod}}_{g} \cdot \left( u_{\xi,t,g} - \gamma_{\xi,g} \cdot \mu^{u}_{\xi,t,g} \right) \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{com}_{g} \wedge \mathrm{p}^{\mathrm{mod}}_{g} > 0 \wedge \mathrm{on}_{t,g}
+p_{\xi,t,g} \le \overline{\mathrm{p}}_{\xi,t,g} \cdot \mathrm{p}^{\mathrm{mod}}_{g} \cdot \left( u_{\xi,t,g} - \gamma_{\xi,g} \cdot \mu^{u}_{\xi,t,g} \right) \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{on}^{\mathrm{com}}_{t,g} \wedge \mathrm{p}^{\mathrm{mod}}_{g} > 0
 ```
 
 ### `Generator-status-p-fixed-upper`
@@ -6623,12 +6638,12 @@ Generator_status_p_fixed_upper:
     place, an explicit row as PyPSA writes it: one where the build is not
     modular, and the fixed build's whole count of modules where it is
   dims: [scenario, snapshot, generator]
-  where: Generator_committable AND NOT (Generator_p_nom_extendable AND Generator_p_nom_mod > 0) AND Generator_active
+  where: Generator_committed AND NOT (Generator_p_nom_extendable AND Generator_p_nom_mod > 0)
   expression: Generator_status <= Generator_modules_installed
 ```
 
 ```math
-u_{\xi,t,g} \le \mathrm{N}^{\mathrm{fix}}_{\xi,g} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{com}_{g} \wedge \neg \left( \mathrm{ext}_{g} \wedge \mathrm{p}^{\mathrm{mod}}_{g} > 0 \right) \wedge \mathrm{on}_{t,g}
+u_{\xi,t,g} \le \mathrm{N}^{\mathrm{fix}}_{\xi,g} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{on}^{\mathrm{com}}_{t,g} \wedge \neg \left( \mathrm{ext}_{g} \wedge \mathrm{p}^{\mathrm{mod}}_{g} > 0 \right)
 ```
 
 ### `Generator-start_up-p-fixed-upper`
@@ -6642,12 +6657,12 @@ Generator_start_up_p_fixed_upper:
     place, an explicit row as PyPSA writes it: one where the build is not
     modular, and the fixed build's whole count of modules where it is
   dims: [scenario, snapshot, generator]
-  where: Generator_committable AND NOT (Generator_p_nom_extendable AND Generator_p_nom_mod > 0) AND Generator_active
+  where: Generator_committed AND NOT (Generator_p_nom_extendable AND Generator_p_nom_mod > 0)
   expression: Generator_start_up <= Generator_modules_installed
 ```
 
 ```math
-\mathit{up}_{\xi,t,g} \le \mathrm{N}^{\mathrm{fix}}_{\xi,g} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{com}_{g} \wedge \neg \left( \mathrm{ext}_{g} \wedge \mathrm{p}^{\mathrm{mod}}_{g} > 0 \right) \wedge \mathrm{on}_{t,g}
+\mathit{up}_{\xi,t,g} \le \mathrm{N}^{\mathrm{fix}}_{\xi,g} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{on}^{\mathrm{com}}_{t,g} \wedge \neg \left( \mathrm{ext}_{g} \wedge \mathrm{p}^{\mathrm{mod}}_{g} > 0 \right)
 ```
 
 ### `Generator-shut_down-p-fixed-upper`
@@ -6661,12 +6676,12 @@ Generator_shut_down_p_fixed_upper:
     place, an explicit row as PyPSA writes it: one where the build is not
     modular, and the fixed build's whole count of modules where it is
   dims: [scenario, snapshot, generator]
-  where: Generator_committable AND NOT (Generator_p_nom_extendable AND Generator_p_nom_mod > 0) AND Generator_active
+  where: Generator_committed AND NOT (Generator_p_nom_extendable AND Generator_p_nom_mod > 0)
   expression: Generator_shut_down <= Generator_modules_installed
 ```
 
 ```math
-\mathit{dn}_{\xi,t,g} \le \mathrm{N}^{\mathrm{fix}}_{\xi,g} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{com}_{g} \wedge \neg \left( \mathrm{ext}_{g} \wedge \mathrm{p}^{\mathrm{mod}}_{g} > 0 \right) \wedge \mathrm{on}_{t,g}
+\mathit{dn}_{\xi,t,g} \le \mathrm{N}^{\mathrm{fix}}_{\xi,g} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{on}^{\mathrm{com}}_{t,g} \wedge \neg \left( \mathrm{ext}_{g} \wedge \mathrm{p}^{\mathrm{mod}}_{g} > 0 \right)
 ```
 
 ### `Generator-status-p_nom-variable-upper`
@@ -6677,12 +6692,12 @@ Generator_shut_down_p_fixed_upper:
 Generator_status_p_nom_variable_upper:
   description: "`Generator-status-p_nom-variable-upper` — a modular unit is on only where a module is built"
   dims: [scenario, snapshot, generator]
-  where: Generator_committable AND Generator_p_nom_extendable AND Generator_p_nom_mod > 0 AND Generator_active
+  where: Generator_committed AND Generator_p_nom_extendable AND Generator_p_nom_mod > 0
   expression: Generator_status <= Generator_n_mod
 ```
 
 ```math
-u_{\xi,t,g} \le N_{g} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{com}_{g} \wedge \mathrm{ext}_{g} \wedge \mathrm{p}^{\mathrm{mod}}_{g} > 0 \wedge \mathrm{on}_{t,g}
+u_{\xi,t,g} \le N_{g} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{on}^{\mathrm{com}}_{t,g} \wedge \mathrm{ext}_{g} \wedge \mathrm{p}^{\mathrm{mod}}_{g} > 0
 ```
 
 ### `Generator-start_up-p_nom-variable-upper`
@@ -6693,12 +6708,12 @@ u_{\xi,t,g} \le N_{g} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \
 Generator_start_up_p_nom_variable_upper:
   description: "`Generator-start_up-p_nom-variable-upper` — a modular unit starts only where a module is built"
   dims: [scenario, snapshot, generator]
-  where: Generator_committable AND Generator_p_nom_extendable AND Generator_p_nom_mod > 0 AND Generator_active
+  where: Generator_committed AND Generator_p_nom_extendable AND Generator_p_nom_mod > 0
   expression: Generator_start_up <= Generator_n_mod
 ```
 
 ```math
-\mathit{up}_{\xi,t,g} \le N_{g} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{com}_{g} \wedge \mathrm{ext}_{g} \wedge \mathrm{p}^{\mathrm{mod}}_{g} > 0 \wedge \mathrm{on}_{t,g}
+\mathit{up}_{\xi,t,g} \le N_{g} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{on}^{\mathrm{com}}_{t,g} \wedge \mathrm{ext}_{g} \wedge \mathrm{p}^{\mathrm{mod}}_{g} > 0
 ```
 
 ### `Generator-shut_down-p_nom-variable-upper`
@@ -6709,12 +6724,12 @@ Generator_start_up_p_nom_variable_upper:
 Generator_shut_down_p_nom_variable_upper:
   description: "`Generator-shut_down-p_nom-variable-upper` — a modular unit stops only where a module is built"
   dims: [scenario, snapshot, generator]
-  where: Generator_committable AND Generator_p_nom_extendable AND Generator_p_nom_mod > 0 AND Generator_active
+  where: Generator_committed AND Generator_p_nom_extendable AND Generator_p_nom_mod > 0
   expression: Generator_shut_down <= Generator_n_mod
 ```
 
 ```math
-\mathit{dn}_{\xi,t,g} \le N_{g} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{com}_{g} \wedge \mathrm{ext}_{g} \wedge \mathrm{p}^{\mathrm{mod}}_{g} > 0 \wedge \mathrm{on}_{t,g}
+\mathit{dn}_{\xi,t,g} \le N_{g} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{on}^{\mathrm{com}}_{t,g} \wedge \mathrm{ext}_{g} \wedge \mathrm{p}^{\mathrm{mod}}_{g} > 0
 ```
 
 ### `Generator-maint-event-count`
@@ -6778,12 +6793,12 @@ Generator_maintcap_upper:
     `Generator-maintcap_upper` — the build taken off is at most the chosen build in
     maintenance, and at most the build less its floor out of it
   dims: [scenario, snapshot, generator]
-  where: Generator_maintainable AND Generator_p_nom_extendable AND NOT (Generator_committable AND Generator_p_nom_mod > 0) AND Generator_active
+  where: Generator_maint_ext
   expression: Generator_maintenance_capacity <= Generator_p_nom_ext - Generator_p_nom_min * (1 - Generator_maintenance)
 ```
 
 ```math
-\mu^{\mathrm{nom}}_{\xi,t,g} \le P_{g} - \underline{\mathrm{p}}^{\mathrm{nom}}_{\xi,g} \cdot \left( 1 - \mu_{\xi,t,g} \right) \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{mnt}_{g} \wedge \mathrm{ext}_{g} \wedge \neg \left( \mathrm{com}_{g} \wedge \mathrm{p}^{\mathrm{mod}}_{g} > 0 \right) \wedge \mathrm{on}_{t,g}
+\mu^{\mathrm{nom}}_{\xi,t,g} \le P_{g} - \underline{\mathrm{p}}^{\mathrm{nom}}_{\xi,g} \cdot \left( 1 - \mu_{\xi,t,g} \right) \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{on}^{\mathrm{mnt,ext}}_{t,g}
 ```
 
 ### `Generator-maintcap_upper_nommax`
@@ -6794,12 +6809,12 @@ Generator_maintcap_upper:
 Generator_maintcap_upper_nommax:
   description: "`Generator-maintcap_upper_nommax` — out of maintenance, no build is taken off"
   dims: [scenario, snapshot, generator]
-  where: Generator_maintainable AND Generator_p_nom_extendable AND NOT (Generator_committable AND Generator_p_nom_mod > 0) AND Generator_active
+  where: Generator_maint_ext
   expression: Generator_maintenance_capacity <= Generator_p_nom_max * Generator_maintenance
 ```
 
 ```math
-\mu^{\mathrm{nom}}_{\xi,t,g} \le \overline{\mathrm{p}}^{\mathrm{nom}}_{\xi,g} \cdot \mu_{\xi,t,g} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{mnt}_{g} \wedge \mathrm{ext}_{g} \wedge \neg \left( \mathrm{com}_{g} \wedge \mathrm{p}^{\mathrm{mod}}_{g} > 0 \right) \wedge \mathrm{on}_{t,g}
+\mu^{\mathrm{nom}}_{\xi,t,g} \le \overline{\mathrm{p}}^{\mathrm{nom}}_{\xi,g} \cdot \mu_{\xi,t,g} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{on}^{\mathrm{mnt,ext}}_{t,g}
 ```
 
 ### `Generator-maintcap_lower_nommax`
@@ -6810,12 +6825,12 @@ Generator_maintcap_upper_nommax:
 Generator_maintcap_lower_nommax:
   description: "`Generator-maintcap_lower_nommax` — in maintenance, the whole chosen build is taken off"
   dims: [scenario, snapshot, generator]
-  where: Generator_maintainable AND Generator_p_nom_extendable AND NOT (Generator_committable AND Generator_p_nom_mod > 0) AND Generator_active
+  where: Generator_maint_ext
   expression: Generator_maintenance_capacity >= Generator_p_nom_ext - Generator_p_nom_max * (1 - Generator_maintenance)
 ```
 
 ```math
-\mu^{\mathrm{nom}}_{\xi,t,g} \ge P_{g} - \overline{\mathrm{p}}^{\mathrm{nom}}_{\xi,g} \cdot \left( 1 - \mu_{\xi,t,g} \right) \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{mnt}_{g} \wedge \mathrm{ext}_{g} \wedge \neg \left( \mathrm{com}_{g} \wedge \mathrm{p}^{\mathrm{mod}}_{g} > 0 \right) \wedge \mathrm{on}_{t,g}
+\mu^{\mathrm{nom}}_{\xi,t,g} \ge P_{g} - \overline{\mathrm{p}}^{\mathrm{nom}}_{\xi,g} \cdot \left( 1 - \mu_{\xi,t,g} \right) \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{on}^{\mathrm{mnt,ext}}_{t,g}
 ```
 
 ### `Generator-maintcap_lower_nommin`
@@ -6826,12 +6841,12 @@ Generator_maintcap_lower_nommax:
 Generator_maintcap_lower_nommin:
   description: "`Generator-maintcap_lower_nommin` — in maintenance, at least the floor of the build is taken off"
   dims: [scenario, snapshot, generator]
-  where: Generator_maintainable AND Generator_p_nom_extendable AND NOT (Generator_committable AND Generator_p_nom_mod > 0) AND Generator_active AND Generator_p_nom_min > 0
+  where: Generator_maint_ext AND Generator_p_nom_min > 0
   expression: Generator_maintenance_capacity >= Generator_p_nom_min * Generator_maintenance
 ```
 
 ```math
-\mu^{\mathrm{nom}}_{\xi,t,g} \ge \underline{\mathrm{p}}^{\mathrm{nom}}_{\xi,g} \cdot \mu_{\xi,t,g} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{mnt}_{g} \wedge \mathrm{ext}_{g} \wedge \neg \left( \mathrm{com}_{g} \wedge \mathrm{p}^{\mathrm{mod}}_{g} > 0 \right) \wedge \mathrm{on}_{t,g} \wedge \underline{\mathrm{p}}^{\mathrm{nom}}_{\xi,g} > 0
+\mu^{\mathrm{nom}}_{\xi,t,g} \ge \underline{\mathrm{p}}^{\mathrm{nom}}_{\xi,g} \cdot \mu_{\xi,t,g} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{on}^{\mathrm{mnt,ext}}_{t,g} \wedge \underline{\mathrm{p}}^{\mathrm{nom}}_{\xi,g} > 0
 ```
 
 ### `Generator-maint-status-le-status`
@@ -6842,12 +6857,12 @@ Generator_maintcap_lower_nommin:
 Generator_maint_status_le_status:
   description: "`Generator-maint-status-le-status` — the status in maintenance is at most the status"
   dims: [scenario, snapshot, generator]
-  where: Generator_maintainable AND Generator_committable AND NOT Generator_p_nom_extendable AND NOT (Generator_p_nom_mod > 0) AND Generator_active
+  where: Generator_maintainable AND Generator_committed AND NOT Generator_p_nom_extendable AND NOT (Generator_p_nom_mod > 0)
   expression: Generator_maintenance_status <= Generator_status
 ```
 
 ```math
-\mu^{u}_{\xi,t,g} \le u_{\xi,t,g} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{mnt}_{g} \wedge \mathrm{com}_{g} \wedge \neg \mathrm{ext}_{g} \wedge \neg \left( \mathrm{p}^{\mathrm{mod}}_{g} > 0 \right) \wedge \mathrm{on}_{t,g}
+\mu^{u}_{\xi,t,g} \le u_{\xi,t,g} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{mnt}_{g} \wedge \mathrm{on}^{\mathrm{com}}_{t,g} \wedge \neg \mathrm{ext}_{g} \wedge \neg \left( \mathrm{p}^{\mathrm{mod}}_{g} > 0 \right)
 ```
 
 ### `Generator-maint-status-le-maint`
@@ -6858,12 +6873,12 @@ Generator_maint_status_le_status:
 Generator_maint_status_le_maint:
   description: "`Generator-maint-status-le-maint` — out of maintenance, the status in maintenance is zero"
   dims: [scenario, snapshot, generator]
-  where: Generator_maintainable AND Generator_committable AND NOT Generator_p_nom_extendable AND NOT (Generator_p_nom_mod > 0) AND Generator_active
+  where: Generator_maintainable AND Generator_committed AND NOT Generator_p_nom_extendable AND NOT (Generator_p_nom_mod > 0)
   expression: Generator_maintenance_status <= Generator_maintenance
 ```
 
 ```math
-\mu^{u}_{\xi,t,g} \le \mu_{\xi,t,g} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{mnt}_{g} \wedge \mathrm{com}_{g} \wedge \neg \mathrm{ext}_{g} \wedge \neg \left( \mathrm{p}^{\mathrm{mod}}_{g} > 0 \right) \wedge \mathrm{on}_{t,g}
+\mu^{u}_{\xi,t,g} \le \mu_{\xi,t,g} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{mnt}_{g} \wedge \mathrm{on}^{\mathrm{com}}_{t,g} \wedge \neg \mathrm{ext}_{g} \wedge \neg \left( \mathrm{p}^{\mathrm{mod}}_{g} > 0 \right)
 ```
 
 ### `Generator-maint-status-lb`
@@ -6874,12 +6889,12 @@ Generator_maint_status_le_maint:
 Generator_maint_status_lb:
   description: "`Generator-maint-status-lb` — on and in maintenance, the status in maintenance is one"
   dims: [scenario, snapshot, generator]
-  where: Generator_maintainable AND Generator_committable AND NOT Generator_p_nom_extendable AND NOT (Generator_p_nom_mod > 0) AND Generator_active
+  where: Generator_maintainable AND Generator_committed AND NOT Generator_p_nom_extendable AND NOT (Generator_p_nom_mod > 0)
   expression: Generator_maintenance_status >= Generator_status + Generator_maintenance - 1
 ```
 
 ```math
-\mu^{u}_{\xi,t,g} \ge u_{\xi,t,g} + \mu_{\xi,t,g} - 1 \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{mnt}_{g} \wedge \mathrm{com}_{g} \wedge \neg \mathrm{ext}_{g} \wedge \neg \left( \mathrm{p}^{\mathrm{mod}}_{g} > 0 \right) \wedge \mathrm{on}_{t,g}
+\mu^{u}_{\xi,t,g} \ge u_{\xi,t,g} + \mu_{\xi,t,g} - 1 \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{mnt}_{g} \wedge \mathrm{on}^{\mathrm{com}}_{t,g} \wedge \neg \mathrm{ext}_{g} \wedge \neg \left( \mathrm{p}^{\mathrm{mod}}_{g} > 0 \right)
 ```
 
 ### `Generator-maint-modstatus-le-status`
@@ -6890,12 +6905,12 @@ Generator_maint_status_lb:
 Generator_maint_modstatus_le_status:
   description: "`Generator-maint-modstatus-le-status` — the modules on in maintenance are at most the modules on"
   dims: [scenario, snapshot, generator]
-  where: Generator_maintainable AND Generator_committable AND Generator_p_nom_mod > 0 AND Generator_active
+  where: Generator_maintainable AND Generator_committed AND Generator_p_nom_mod > 0
   expression: Generator_maintenance_status <= Generator_status
 ```
 
 ```math
-\mu^{u}_{\xi,t,g} \le u_{\xi,t,g} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{mnt}_{g} \wedge \mathrm{com}_{g} \wedge \mathrm{p}^{\mathrm{mod}}_{g} > 0 \wedge \mathrm{on}_{t,g}
+\mu^{u}_{\xi,t,g} \le u_{\xi,t,g} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{mnt}_{g} \wedge \mathrm{on}^{\mathrm{com}}_{t,g} \wedge \mathrm{p}^{\mathrm{mod}}_{g} > 0
 ```
 
 ### `Generator-maint-modstatus-le-maint`
@@ -6908,12 +6923,12 @@ Generator_maint_modstatus_le_maint:
     `Generator-maint-modstatus-le-maint` — out of maintenance, no module is on in
     maintenance; in it, at most the modules the build cap holds
   dims: [scenario, snapshot, generator]
-  where: Generator_maintainable AND Generator_committable AND Generator_p_nom_mod > 0 AND Generator_active
+  where: Generator_maintainable AND Generator_committed AND Generator_p_nom_mod > 0
   expression: Generator_maintenance_status <= Generator_p_nom_max / Generator_p_nom_mod * Generator_maintenance
 ```
 
 ```math
-\mu^{u}_{\xi,t,g} \le \frac{\overline{\mathrm{p}}^{\mathrm{nom}}_{\xi,g}}{\mathrm{p}^{\mathrm{mod}}_{g}} \cdot \mu_{\xi,t,g} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{mnt}_{g} \wedge \mathrm{com}_{g} \wedge \mathrm{p}^{\mathrm{mod}}_{g} > 0 \wedge \mathrm{on}_{t,g}
+\mu^{u}_{\xi,t,g} \le \frac{\overline{\mathrm{p}}^{\mathrm{nom}}_{\xi,g}}{\mathrm{p}^{\mathrm{mod}}_{g}} \cdot \mu_{\xi,t,g} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{mnt}_{g} \wedge \mathrm{on}^{\mathrm{com}}_{t,g} \wedge \mathrm{p}^{\mathrm{mod}}_{g} > 0
 ```
 
 ### `Generator-maint-modstatus-lb`
@@ -6924,12 +6939,12 @@ Generator_maint_modstatus_le_maint:
 Generator_maint_modstatus_lb:
   description: "`Generator-maint-modstatus-lb` — in maintenance, every module on is on in maintenance"
   dims: [scenario, snapshot, generator]
-  where: Generator_maintainable AND Generator_committable AND Generator_p_nom_mod > 0 AND Generator_active
+  where: Generator_maintainable AND Generator_committed AND Generator_p_nom_mod > 0
   expression: Generator_maintenance_status >= Generator_status - Generator_p_nom_max / Generator_p_nom_mod * (1 - Generator_maintenance)
 ```
 
 ```math
-\mu^{u}_{\xi,t,g} \ge u_{\xi,t,g} - \frac{\overline{\mathrm{p}}^{\mathrm{nom}}_{\xi,g}}{\mathrm{p}^{\mathrm{mod}}_{g}} \cdot \left( 1 - \mu_{\xi,t,g} \right) \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{mnt}_{g} \wedge \mathrm{com}_{g} \wedge \mathrm{p}^{\mathrm{mod}}_{g} > 0 \wedge \mathrm{on}_{t,g}
+\mu^{u}_{\xi,t,g} \ge u_{\xi,t,g} - \frac{\overline{\mathrm{p}}^{\mathrm{nom}}_{\xi,g}}{\mathrm{p}^{\mathrm{mod}}_{g}} \cdot \left( 1 - \mu_{\xi,t,g} \right) \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{mnt}_{g} \wedge \mathrm{on}^{\mathrm{com}}_{t,g} \wedge \mathrm{p}^{\mathrm{mod}}_{g} > 0
 ```
 
 ### `Link-com-p-lower`
@@ -6940,12 +6955,12 @@ Generator_maint_modstatus_lb:
 Link_com_p_lower:
   description: "`Link-com-p-lower` — a committed link flows at least its minimum; off, at least nothing"
   dims: [scenario, snapshot, link]
-  where: Link_committable AND not Link_p_nom_extendable AND NOT (Link_p_nom_mod > 0) AND Link_active
+  where: Link_committed AND NOT Link_p_nom_extendable AND NOT (Link_p_nom_mod > 0)
   expression: Link_p >= Link_p_min_pu * Link_p_nom * (Link_status - Link_maintenance_pu * Link_maintenance_status)
 ```
 
 ```math
-f_{\xi,t,l} \ge \underline{\mathrm{f}}_{\xi,t,l} \cdot \mathrm{f}^{\mathrm{nom}}_{\xi,l} \cdot \left( u^{f}_{\xi,t,l} - \gamma^{f}_{\xi,l} \cdot \mu^{f,u}_{\xi,t,l} \right) \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{com}^{f}_{l} \wedge \neg \mathrm{ext}^{f}_{l} \wedge \neg \left( \mathrm{f}^{\mathrm{mod}}_{l} > 0 \right) \wedge \mathrm{on}^{f}_{t,l}
+f_{\xi,t,l} \ge \underline{\mathrm{f}}_{\xi,t,l} \cdot \mathrm{f}^{\mathrm{nom}}_{\xi,l} \cdot \left( u^{f}_{\xi,t,l} - \gamma^{f}_{\xi,l} \cdot \mu^{f,u}_{\xi,t,l} \right) \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{on}^{f,\mathrm{com}}_{t,l} \wedge \neg \mathrm{ext}^{f}_{l} \wedge \neg \left( \mathrm{f}^{\mathrm{mod}}_{l} > 0 \right)
 ```
 
 ### `Link-com-p-upper`
@@ -6956,12 +6971,12 @@ f_{\xi,t,l} \ge \underline{\mathrm{f}}_{\xi,t,l} \cdot \mathrm{f}^{\mathrm{nom}}
 Link_com_p_upper:
   description: "`Link-com-p-upper` — a committed link flows at most what is available; off, at most nothing"
   dims: [scenario, snapshot, link]
-  where: Link_committable AND not Link_p_nom_extendable AND NOT (Link_p_nom_mod > 0) AND Link_active
+  where: Link_committed AND NOT Link_p_nom_extendable AND NOT (Link_p_nom_mod > 0)
   expression: Link_p <= Link_p_max_pu * Link_p_nom * (Link_status - Link_maintenance_pu * Link_maintenance_status)
 ```
 
 ```math
-f_{\xi,t,l} \le \overline{\mathrm{f}}_{\xi,t,l} \cdot \mathrm{f}^{\mathrm{nom}}_{\xi,l} \cdot \left( u^{f}_{\xi,t,l} - \gamma^{f}_{\xi,l} \cdot \mu^{f,u}_{\xi,t,l} \right) \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{com}^{f}_{l} \wedge \neg \mathrm{ext}^{f}_{l} \wedge \neg \left( \mathrm{f}^{\mathrm{mod}}_{l} > 0 \right) \wedge \mathrm{on}^{f}_{t,l}
+f_{\xi,t,l} \le \overline{\mathrm{f}}_{\xi,t,l} \cdot \mathrm{f}^{\mathrm{nom}}_{\xi,l} \cdot \left( u^{f}_{\xi,t,l} - \gamma^{f}_{\xi,l} \cdot \mu^{f,u}_{\xi,t,l} \right) \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{on}^{f,\mathrm{com}}_{t,l} \wedge \neg \mathrm{ext}^{f}_{l} \wedge \neg \left( \mathrm{f}^{\mathrm{mod}}_{l} > 0 \right)
 ```
 
 ### `Link-com-transition-start-up`
@@ -6972,12 +6987,12 @@ f_{\xi,t,l} \le \overline{\mathrm{f}}_{\xi,t,l} \cdot \mathrm{f}^{\mathrm{nom}}_
 Link_com_transition_start_up:
   description: "`Link-com-transition-start-up` — turning on is a start, counted against the state the link carried into the snapshot"
   dims: [scenario, snapshot, link]
-  where: Link_committable AND Link_active
+  where: Link_committed
   expression: Link_start_up >= Link_status - Link_previous_status
 ```
 
 ```math
-\mathit{up}^{f}_{\xi,t,l} \ge u^{f}_{\xi,t,l} - \overleftarrow{u}^{f}_{\xi,t,l} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{com}^{f}_{l} \wedge \mathrm{on}^{f}_{t,l}
+\mathit{up}^{f}_{\xi,t,l} \ge u^{f}_{\xi,t,l} - \overleftarrow{u}^{f}_{\xi,t,l} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{on}^{f,\mathrm{com}}_{t,l}
 ```
 
 ### `Link-com-transition-shut-down`
@@ -6988,12 +7003,12 @@ Link_com_transition_start_up:
 Link_com_transition_shut_down:
   description: "`Link-com-transition-shut-down` — turning off is a stop, counted against the state the link carried into the snapshot"
   dims: [scenario, snapshot, link]
-  where: Link_committable AND Link_active
+  where: Link_committed
   expression: Link_shut_down >= Link_previous_status - Link_status
 ```
 
 ```math
-\mathit{dn}^{f}_{\xi,t,l} \ge \overleftarrow{u}^{f}_{\xi,t,l} - u^{f}_{\xi,t,l} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{com}^{f}_{l} \wedge \mathrm{on}^{f}_{t,l}
+\mathit{dn}^{f}_{\xi,t,l} \ge \overleftarrow{u}^{f}_{\xi,t,l} - u^{f}_{\xi,t,l} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{on}^{f,\mathrm{com}}_{t,l}
 ```
 
 ### `Link-com-up-time`
@@ -7007,12 +7022,12 @@ Link_com_up_time:
     is still on. The first snapshot's share of the window is the brought-in
     up time's, which the must-stay-up mask carries
   dims: [scenario, snapshot, link]
-  where: Link_committable AND Link_min_up_time > 0 AND position(snapshot) > 0 AND Link_active
+  where: Link_committed AND Link_min_up_time > 0 AND position(snapshot) > 0
   expression: sum_back(Link_start_up, along=snapshot, window=Link_min_up_time) <= Link_status
 ```
 
 ```math
-\sum_{t' \in \mathcal{T} \,:\, 0 \le t - t' < \mathrm{UT}^{f}} \mathit{up}^{f}_{\xi,t',l} \le u^{f}_{\xi,t,l} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{com}^{f}_{l} \wedge \mathrm{UT}^{f}_{\xi,l} > 0 \wedge \mathrm{pos}(t) > 0 \wedge \mathrm{on}^{f}_{t,l}
+\sum_{t' \in \mathcal{T} \,:\, 0 \le t - t' < \mathrm{UT}^{f}} \mathit{up}^{f}_{\xi,t',l} \le u^{f}_{\xi,t,l} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{on}^{f,\mathrm{com}}_{t,l} \wedge \mathrm{UT}^{f}_{\xi,l} > 0 \wedge \mathrm{pos}(t) > 0
 ```
 
 ### `Link-com-down-time`
@@ -7026,12 +7041,12 @@ Link_com_down_time:
     time is still off. The first snapshot's share of the window is the
     brought-in down time's, which the must-stay-down mask carries
   dims: [scenario, snapshot, link]
-  where: Link_committable AND Link_min_down_time > 0 AND position(snapshot) > 0 AND Link_active
+  where: Link_committed AND Link_min_down_time > 0 AND position(snapshot) > 0
   expression: sum_back(Link_shut_down, along=snapshot, window=Link_min_down_time) <= 1 - Link_status
 ```
 
 ```math
-\sum_{t' \in \mathcal{T} \,:\, 0 \le t - t' < \mathrm{DT}^{f}} \mathit{dn}^{f}_{\xi,t',l} \le 1 - u^{f}_{\xi,t,l} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{com}^{f}_{l} \wedge \mathrm{DT}^{f}_{\xi,l} > 0 \wedge \mathrm{pos}(t) > 0 \wedge \mathrm{on}^{f}_{t,l}
+\sum_{t' \in \mathcal{T} \,:\, 0 \le t - t' < \mathrm{DT}^{f}} \mathit{dn}^{f}_{\xi,t',l} \le 1 - u^{f}_{\xi,t,l} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{on}^{f,\mathrm{com}}_{t,l} \wedge \mathrm{DT}^{f}_{\xi,l} > 0 \wedge \mathrm{pos}(t) > 0
 ```
 
 ### `Link-com-status-min_up_time_must_stay_up`
@@ -7042,12 +7057,12 @@ Link_com_down_time:
 Link_com_status_must_stay_up:
   description: "`Link-com-status-min_up_time_must_stay_up` — a link still serving the up time it brought in stays on"
   dims: [scenario, snapshot, link]
-  where: Link_committable AND Link_must_stay_up AND Link_active
+  where: Link_committed AND Link_must_stay_up
   expression: Link_status == 1
 ```
 
 ```math
-u^{f}_{\xi,t,l} = 1 \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{com}^{f}_{l} \wedge \mathrm{hold}^{f}_{\xi,t,l} \wedge \mathrm{on}^{f}_{t,l}
+u^{f}_{\xi,t,l} = 1 \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{on}^{f,\mathrm{com}}_{t,l} \wedge \mathrm{hold}^{f}_{\xi,t,l}
 ```
 
 ### `Link-com-status-min_down_time_must_stay_up`
@@ -7060,12 +7075,12 @@ Link_com_status_must_stay_down:
     `Link-com-status-min_down_time_must_stay_up` — a link still serving
     the down time it brought in stays off; PyPSA names the row `_must_stay_up`
   dims: [scenario, snapshot, link]
-  where: Link_committable AND Link_must_stay_down AND Link_active
+  where: Link_committed AND Link_must_stay_down
   expression: Link_status == 0
 ```
 
 ```math
-u^{f}_{\xi,t,l} = 0 \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{com}^{f}_{l} \wedge \mathrm{rest}^{f}_{\xi,t,l} \wedge \mathrm{on}^{f}_{t,l}
+u^{f}_{\xi,t,l} = 0 \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{on}^{f,\mathrm{com}}_{t,l} \wedge \mathrm{rest}^{f}_{\xi,t,l}
 ```
 
 ### `Link-p-ramp_limit_up-run-bigM`
@@ -7079,11 +7094,7 @@ Link_p_ramp_limit_up_run_big_m:
     raises flow no faster than its limit of the chosen build; the big M
     releases the row in the snapshot it turns on
   dims: [scenario, snapshot, link]
-  where: >-
-    Link_committable AND Link_p_nom_extendable AND NOT (Link_p_nom_mod > 0)
-    AND (Link_ramp_limit_up OR Link_ramp_limit_start_up)
-    AND (position(snapshot, within=snapshot_period[period]) > 0 OR (position(snapshot) == 0 AND (Link_status_initial == 0 OR Link_p_init)))
-    AND Link_active
+  where: Link_com_ext AND (Link_ramp_limit_up OR Link_ramp_limit_start_up) AND Link_ramps_from_previous
   expression: >-
     Link_p - Link_previous_p <=
     Link_ramp_up_rate * Link_p_nom_ext
@@ -7091,7 +7102,7 @@ Link_p_ramp_limit_up_run_big_m:
 ```
 
 ```math
-f_{\xi,t,l} - \overleftarrow{f}_{\xi,t,l} \le \widetilde{\mathrm{ru}}^{f}_{\xi,t,l} \cdot F_{l} + \mathrm{M}^{f}_{\xi,l} - \mathrm{M}^{f}_{\xi,l} \cdot \overleftarrow{u}^{f}_{\xi,t,l} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{com}^{f}_{l} \wedge \mathrm{ext}^{f}_{l} \wedge \neg \left( \mathrm{f}^{\mathrm{mod}}_{l} > 0 \right) \wedge \left( \mathrm{ru}^{f}_{\xi,t,l} \text{ is defined} \vee \mathrm{ru}^{f,\mathrm{up}}_{\xi,l} \text{ is defined} \right) \wedge \left( \mathrm{pos}_{\mathrm{snapshot\_period}(t)}(t) > 0 \vee \mathrm{pos}(t) = 0 \wedge \left( \mathrm{u}^{f,0}_{\xi,l} = 0 \vee \mathrm{f}^{0}_{\xi,l} \text{ is defined} \right) \right) \wedge \mathrm{on}^{f}_{t,l}
+f_{\xi,t,l} - \overleftarrow{f}_{\xi,t,l} \le \widetilde{\mathrm{ru}}^{f}_{\xi,t,l} \cdot F_{l} + \mathrm{M}^{f}_{\xi,l} - \mathrm{M}^{f}_{\xi,l} \cdot \overleftarrow{u}^{f}_{\xi,t,l} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{on}^{f,\mathrm{com,ext}}_{t,l} \wedge \left( \mathrm{ru}^{f}_{\xi,t,l} \text{ is defined} \vee \mathrm{ru}^{f,\mathrm{up}}_{\xi,l} \text{ is defined} \right) \wedge \mathrm{prev}^{f}_{\xi,t,l}
 ```
 
 ### `Link-p-ramp_limit_up-start-bigM`
@@ -7105,11 +7116,7 @@ Link_p_ramp_limit_up_start_big_m:
     committed extendable link ramps no further than its start-up ramp of
     the chosen build; the big M releases the row everywhere else
   dims: [scenario, snapshot, link]
-  where: >-
-    Link_committable AND Link_p_nom_extendable AND NOT (Link_p_nom_mod > 0)
-    AND (Link_ramp_limit_up OR Link_ramp_limit_start_up)
-    AND (position(snapshot, within=snapshot_period[period]) > 0 OR (position(snapshot) == 0 AND (Link_status_initial == 0 OR Link_p_init)))
-    AND Link_active
+  where: Link_com_ext AND (Link_ramp_limit_up OR Link_ramp_limit_start_up) AND Link_ramps_from_previous
   expression: >-
     Link_p - Link_previous_p <=
     Link_start_up_rate * Link_p_nom_ext
@@ -7117,7 +7124,7 @@ Link_p_ramp_limit_up_start_big_m:
 ```
 
 ```math
-f_{\xi,t,l} - \overleftarrow{f}_{\xi,t,l} \le \widetilde{\mathrm{ru}}^{f,\mathrm{up}}_{\xi,l} \cdot F_{l} + \mathrm{M}^{f}_{\xi,l} - \mathrm{M}^{f}_{\xi,l} \cdot \mathit{up}^{f}_{\xi,t,l} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{com}^{f}_{l} \wedge \mathrm{ext}^{f}_{l} \wedge \neg \left( \mathrm{f}^{\mathrm{mod}}_{l} > 0 \right) \wedge \left( \mathrm{ru}^{f}_{\xi,t,l} \text{ is defined} \vee \mathrm{ru}^{f,\mathrm{up}}_{\xi,l} \text{ is defined} \right) \wedge \left( \mathrm{pos}_{\mathrm{snapshot\_period}(t)}(t) > 0 \vee \mathrm{pos}(t) = 0 \wedge \left( \mathrm{u}^{f,0}_{\xi,l} = 0 \vee \mathrm{f}^{0}_{\xi,l} \text{ is defined} \right) \right) \wedge \mathrm{on}^{f}_{t,l}
+f_{\xi,t,l} - \overleftarrow{f}_{\xi,t,l} \le \widetilde{\mathrm{ru}}^{f,\mathrm{up}}_{\xi,l} \cdot F_{l} + \mathrm{M}^{f}_{\xi,l} - \mathrm{M}^{f}_{\xi,l} \cdot \mathit{up}^{f}_{\xi,t,l} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{on}^{f,\mathrm{com,ext}}_{t,l} \wedge \left( \mathrm{ru}^{f}_{\xi,t,l} \text{ is defined} \vee \mathrm{ru}^{f,\mathrm{up}}_{\xi,l} \text{ is defined} \right) \wedge \mathrm{prev}^{f}_{\xi,t,l}
 ```
 
 ### `Link-p-ramp_limit_down-run-bigM`
@@ -7131,11 +7138,7 @@ Link_p_ramp_limit_down_run_big_m:
     lowers flow no faster than its limit of the chosen build; the big M
     releases the row in the snapshot it turns off
   dims: [scenario, snapshot, link]
-  where: >-
-    Link_committable AND Link_p_nom_extendable AND NOT (Link_p_nom_mod > 0)
-    AND (Link_ramp_limit_down OR Link_ramp_limit_shut_down)
-    AND (position(snapshot, within=snapshot_period[period]) > 0 OR (position(snapshot) == 0 AND (Link_status_initial == 0 OR Link_p_init)))
-    AND Link_active
+  where: Link_com_ext AND (Link_ramp_limit_down OR Link_ramp_limit_shut_down) AND Link_ramps_from_previous
   expression: >-
     Link_previous_p - Link_p <=
     Link_ramp_down_rate * Link_p_nom_ext
@@ -7143,7 +7146,7 @@ Link_p_ramp_limit_down_run_big_m:
 ```
 
 ```math
-\overleftarrow{f}_{\xi,t,l} - f_{\xi,t,l} \le \widetilde{\mathrm{rd}}^{f}_{\xi,t,l} \cdot F_{l} + \mathrm{M}^{f}_{\xi,l} - \mathrm{M}^{f}_{\xi,l} \cdot u^{f}_{\xi,t,l} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{com}^{f}_{l} \wedge \mathrm{ext}^{f}_{l} \wedge \neg \left( \mathrm{f}^{\mathrm{mod}}_{l} > 0 \right) \wedge \left( \mathrm{rd}^{f}_{\xi,t,l} \text{ is defined} \vee \mathrm{rd}^{f,\mathrm{dn}}_{\xi,l} \text{ is defined} \right) \wedge \left( \mathrm{pos}_{\mathrm{snapshot\_period}(t)}(t) > 0 \vee \mathrm{pos}(t) = 0 \wedge \left( \mathrm{u}^{f,0}_{\xi,l} = 0 \vee \mathrm{f}^{0}_{\xi,l} \text{ is defined} \right) \right) \wedge \mathrm{on}^{f}_{t,l}
+\overleftarrow{f}_{\xi,t,l} - f_{\xi,t,l} \le \widetilde{\mathrm{rd}}^{f}_{\xi,t,l} \cdot F_{l} + \mathrm{M}^{f}_{\xi,l} - \mathrm{M}^{f}_{\xi,l} \cdot u^{f}_{\xi,t,l} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{on}^{f,\mathrm{com,ext}}_{t,l} \wedge \left( \mathrm{rd}^{f}_{\xi,t,l} \text{ is defined} \vee \mathrm{rd}^{f,\mathrm{dn}}_{\xi,l} \text{ is defined} \right) \wedge \mathrm{prev}^{f}_{\xi,t,l}
 ```
 
 ### `Link-p-ramp_limit_down-shut-bigM`
@@ -7157,11 +7160,7 @@ Link_p_ramp_limit_down_shut_big_m:
     a committed extendable link ramps no further than its shut-down ramp of
     the chosen build; the big M releases the row everywhere else
   dims: [scenario, snapshot, link]
-  where: >-
-    Link_committable AND Link_p_nom_extendable AND NOT (Link_p_nom_mod > 0)
-    AND (Link_ramp_limit_down OR Link_ramp_limit_shut_down)
-    AND (position(snapshot, within=snapshot_period[period]) > 0 OR (position(snapshot) == 0 AND (Link_status_initial == 0 OR Link_p_init)))
-    AND Link_active
+  where: Link_com_ext AND (Link_ramp_limit_down OR Link_ramp_limit_shut_down) AND Link_ramps_from_previous
   expression: >-
     Link_previous_p - Link_p <=
     Link_shut_down_rate * Link_p_nom_ext
@@ -7169,7 +7168,7 @@ Link_p_ramp_limit_down_shut_big_m:
 ```
 
 ```math
-\overleftarrow{f}_{\xi,t,l} - f_{\xi,t,l} \le \widetilde{\mathrm{rd}}^{f,\mathrm{dn}}_{\xi,l} \cdot F_{l} + \mathrm{M}^{f}_{\xi,l} - \mathrm{M}^{f}_{\xi,l} \cdot \mathit{dn}^{f}_{\xi,t,l} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{com}^{f}_{l} \wedge \mathrm{ext}^{f}_{l} \wedge \neg \left( \mathrm{f}^{\mathrm{mod}}_{l} > 0 \right) \wedge \left( \mathrm{rd}^{f}_{\xi,t,l} \text{ is defined} \vee \mathrm{rd}^{f,\mathrm{dn}}_{\xi,l} \text{ is defined} \right) \wedge \left( \mathrm{pos}_{\mathrm{snapshot\_period}(t)}(t) > 0 \vee \mathrm{pos}(t) = 0 \wedge \left( \mathrm{u}^{f,0}_{\xi,l} = 0 \vee \mathrm{f}^{0}_{\xi,l} \text{ is defined} \right) \right) \wedge \mathrm{on}^{f}_{t,l}
+\overleftarrow{f}_{\xi,t,l} - f_{\xi,t,l} \le \widetilde{\mathrm{rd}}^{f,\mathrm{dn}}_{\xi,l} \cdot F_{l} + \mathrm{M}^{f}_{\xi,l} - \mathrm{M}^{f}_{\xi,l} \cdot \mathit{dn}^{f}_{\xi,t,l} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{on}^{f,\mathrm{com,ext}}_{t,l} \wedge \left( \mathrm{rd}^{f}_{\xi,t,l} \text{ is defined} \vee \mathrm{rd}^{f,\mathrm{dn}}_{\xi,l} \text{ is defined} \right) \wedge \mathrm{prev}^{f}_{\xi,t,l}
 ```
 
 ### `Link-p_nom_modularity`
@@ -7198,12 +7197,12 @@ Link_com_ext_p_upper_cap:
     `Link-com-ext-p-upper-cap` — a committed extendable link flows
     at most what is available of the chosen build, whatever its status
   dims: [scenario, snapshot, link]
-  where: Link_committable AND Link_p_nom_extendable AND NOT (Link_p_nom_mod > 0) AND Link_active
+  where: Link_com_ext
   expression: Link_p <= Link_p_max_pu * (Link_p_nom_ext - Link_maintenance_pu * Link_maintenance_capacity)
 ```
 
 ```math
-f_{\xi,t,l} \le \overline{\mathrm{f}}_{\xi,t,l} \cdot \left( F_{l} - \gamma^{f}_{\xi,l} \cdot \mu^{f,\mathrm{nom}}_{\xi,t,l} \right) \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{com}^{f}_{l} \wedge \mathrm{ext}^{f}_{l} \wedge \neg \left( \mathrm{f}^{\mathrm{mod}}_{l} > 0 \right) \wedge \mathrm{on}^{f}_{t,l}
+f_{\xi,t,l} \le \overline{\mathrm{f}}_{\xi,t,l} \cdot \left( F_{l} - \gamma^{f}_{\xi,l} \cdot \mu^{f,\mathrm{nom}}_{\xi,t,l} \right) \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{on}^{f,\mathrm{com,ext}}_{t,l}
 ```
 
 ### `Link-com-ext-p-upper-bigM`
@@ -7214,12 +7213,12 @@ f_{\xi,t,l} \le \overline{\mathrm{f}}_{\xi,t,l} \cdot \left( F_{l} - \gamma^{f}_
 Link_com_ext_p_upper_big_m:
   description: "`Link-com-ext-p-upper-bigM` — off, a link flows nothing; on, the big M is no bound"
   dims: [scenario, snapshot, link]
-  where: Link_committable AND Link_p_nom_extendable AND NOT (Link_p_nom_mod > 0) AND Link_active
+  where: Link_com_ext
   expression: Link_p <= Link_big_m * Link_status
 ```
 
 ```math
-f_{\xi,t,l} \le \mathrm{M}^{f}_{\xi,l} \cdot u^{f}_{\xi,t,l} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{com}^{f}_{l} \wedge \mathrm{ext}^{f}_{l} \wedge \neg \left( \mathrm{f}^{\mathrm{mod}}_{l} > 0 \right) \wedge \mathrm{on}^{f}_{t,l}
+f_{\xi,t,l} \le \mathrm{M}^{f}_{\xi,l} \cdot u^{f}_{\xi,t,l} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{on}^{f,\mathrm{com,ext}}_{t,l}
 ```
 
 ### `Link-com-ext-p-lower`
@@ -7232,7 +7231,7 @@ Link_com_ext_p_lower:
     `Link-com-ext-p-lower` — a committed extendable link flows at
     least its minimum of the chosen build; off, the big M releases the row
   dims: [scenario, snapshot, link]
-  where: Link_committable AND Link_p_nom_extendable AND NOT (Link_p_nom_mod > 0) AND Link_active
+  where: Link_com_ext
   expression: >-
     Link_p >=
     Link_p_min_pu * (Link_p_nom_ext - Link_maintenance_pu * Link_maintenance_capacity)
@@ -7240,7 +7239,7 @@ Link_com_ext_p_lower:
 ```
 
 ```math
-f_{\xi,t,l} \ge \underline{\mathrm{f}}_{\xi,t,l} \cdot \left( F_{l} - \gamma^{f}_{\xi,l} \cdot \mu^{f,\mathrm{nom}}_{\xi,t,l} \right) + \mathrm{M}^{f}_{\xi,l} \cdot u^{f}_{\xi,t,l} - \mathrm{M}^{f}_{\xi,l} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{com}^{f}_{l} \wedge \mathrm{ext}^{f}_{l} \wedge \neg \left( \mathrm{f}^{\mathrm{mod}}_{l} > 0 \right) \wedge \mathrm{on}^{f}_{t,l}
+f_{\xi,t,l} \ge \underline{\mathrm{f}}_{\xi,t,l} \cdot \left( F_{l} - \gamma^{f}_{\xi,l} \cdot \mu^{f,\mathrm{nom}}_{\xi,t,l} \right) + \mathrm{M}^{f}_{\xi,l} \cdot u^{f}_{\xi,t,l} - \mathrm{M}^{f}_{\xi,l} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{on}^{f,\mathrm{com,ext}}_{t,l}
 ```
 
 ### `Link-com-ext-p-lower-nonneg`
@@ -7254,14 +7253,12 @@ Link_com_ext_p_lower_nonneg:
     negative, flow is also plainly non-negative, a row the big-M lower
     cannot assert while the link is off
   dims: [scenario, snapshot, link]
-  where: >-
-    Link_committable AND Link_p_nom_extendable
-    AND Link_p_min_pu_nonneg AND NOT (Link_p_nom_mod > 0) AND Link_active
+  where: Link_com_ext AND Link_p_min_pu_nonneg
   expression: Link_p >= 0
 ```
 
 ```math
-f_{\xi,t,l} \ge 0 \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{com}^{f}_{l} \wedge \mathrm{ext}^{f}_{l} \wedge \mathrm{nonneg}^{f}_{l} \wedge \neg \left( \mathrm{f}^{\mathrm{mod}}_{l} > 0 \right) \wedge \mathrm{on}^{f}_{t,l}
+f_{\xi,t,l} \ge 0 \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{on}^{f,\mathrm{com,ext}}_{t,l} \wedge \mathrm{nonneg}^{f}_{l}
 ```
 
 ### `Link-com-mod-p-lower`
@@ -7274,12 +7271,12 @@ Link_com_mod_p_lower:
     `Link-com-mod-p-lower` — a committed modular link flows at least
     its minimum of one module, whether the build is fixed or a decision
   dims: [scenario, snapshot, link]
-  where: Link_committable AND Link_p_nom_mod > 0 AND Link_active
+  where: Link_committed AND Link_p_nom_mod > 0
   expression: Link_p >= Link_p_min_pu * Link_p_nom_mod * (Link_status - Link_maintenance_pu * Link_maintenance_status)
 ```
 
 ```math
-f_{\xi,t,l} \ge \underline{\mathrm{f}}_{\xi,t,l} \cdot \mathrm{f}^{\mathrm{mod}}_{l} \cdot \left( u^{f}_{\xi,t,l} - \gamma^{f}_{\xi,l} \cdot \mu^{f,u}_{\xi,t,l} \right) \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{com}^{f}_{l} \wedge \mathrm{f}^{\mathrm{mod}}_{l} > 0 \wedge \mathrm{on}^{f}_{t,l}
+f_{\xi,t,l} \ge \underline{\mathrm{f}}_{\xi,t,l} \cdot \mathrm{f}^{\mathrm{mod}}_{l} \cdot \left( u^{f}_{\xi,t,l} - \gamma^{f}_{\xi,l} \cdot \mu^{f,u}_{\xi,t,l} \right) \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{on}^{f,\mathrm{com}}_{t,l} \wedge \mathrm{f}^{\mathrm{mod}}_{l} > 0
 ```
 
 ### `Link-com-mod-p-upper`
@@ -7292,12 +7289,12 @@ Link_com_mod_p_upper:
     `Link-com-mod-p-upper` — a committed modular link flows at most
     one module's share, whether the build is fixed or a decision
   dims: [scenario, snapshot, link]
-  where: Link_committable AND Link_p_nom_mod > 0 AND Link_active
+  where: Link_committed AND Link_p_nom_mod > 0
   expression: Link_p <= Link_p_max_pu * Link_p_nom_mod * (Link_status - Link_maintenance_pu * Link_maintenance_status)
 ```
 
 ```math
-f_{\xi,t,l} \le \overline{\mathrm{f}}_{\xi,t,l} \cdot \mathrm{f}^{\mathrm{mod}}_{l} \cdot \left( u^{f}_{\xi,t,l} - \gamma^{f}_{\xi,l} \cdot \mu^{f,u}_{\xi,t,l} \right) \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{com}^{f}_{l} \wedge \mathrm{f}^{\mathrm{mod}}_{l} > 0 \wedge \mathrm{on}^{f}_{t,l}
+f_{\xi,t,l} \le \overline{\mathrm{f}}_{\xi,t,l} \cdot \mathrm{f}^{\mathrm{mod}}_{l} \cdot \left( u^{f}_{\xi,t,l} - \gamma^{f}_{\xi,l} \cdot \mu^{f,u}_{\xi,t,l} \right) \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{on}^{f,\mathrm{com}}_{t,l} \wedge \mathrm{f}^{\mathrm{mod}}_{l} > 0
 ```
 
 ### `Link-status-p-fixed-upper`
@@ -7311,12 +7308,12 @@ Link_status_p_fixed_upper:
     place, an explicit row as PyPSA writes it: one where the build is not
     modular, and the fixed build's whole count of modules where it is
   dims: [scenario, snapshot, link]
-  where: Link_committable AND NOT (Link_p_nom_extendable AND Link_p_nom_mod > 0) AND Link_active
+  where: Link_committed AND NOT (Link_p_nom_extendable AND Link_p_nom_mod > 0)
   expression: Link_status <= Link_modules_installed
 ```
 
 ```math
-u^{f}_{\xi,t,l} \le \mathrm{N}^{f,\mathrm{fix}}_{\xi,l} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{com}^{f}_{l} \wedge \neg \left( \mathrm{ext}^{f}_{l} \wedge \mathrm{f}^{\mathrm{mod}}_{l} > 0 \right) \wedge \mathrm{on}^{f}_{t,l}
+u^{f}_{\xi,t,l} \le \mathrm{N}^{f,\mathrm{fix}}_{\xi,l} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{on}^{f,\mathrm{com}}_{t,l} \wedge \neg \left( \mathrm{ext}^{f}_{l} \wedge \mathrm{f}^{\mathrm{mod}}_{l} > 0 \right)
 ```
 
 ### `Link-start_up-p-fixed-upper`
@@ -7330,12 +7327,12 @@ Link_start_up_p_fixed_upper:
     place, an explicit row as PyPSA writes it: one where the build is not
     modular, and the fixed build's whole count of modules where it is
   dims: [scenario, snapshot, link]
-  where: Link_committable AND NOT (Link_p_nom_extendable AND Link_p_nom_mod > 0) AND Link_active
+  where: Link_committed AND NOT (Link_p_nom_extendable AND Link_p_nom_mod > 0)
   expression: Link_start_up <= Link_modules_installed
 ```
 
 ```math
-\mathit{up}^{f}_{\xi,t,l} \le \mathrm{N}^{f,\mathrm{fix}}_{\xi,l} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{com}^{f}_{l} \wedge \neg \left( \mathrm{ext}^{f}_{l} \wedge \mathrm{f}^{\mathrm{mod}}_{l} > 0 \right) \wedge \mathrm{on}^{f}_{t,l}
+\mathit{up}^{f}_{\xi,t,l} \le \mathrm{N}^{f,\mathrm{fix}}_{\xi,l} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{on}^{f,\mathrm{com}}_{t,l} \wedge \neg \left( \mathrm{ext}^{f}_{l} \wedge \mathrm{f}^{\mathrm{mod}}_{l} > 0 \right)
 ```
 
 ### `Link-shut_down-p-fixed-upper`
@@ -7349,12 +7346,12 @@ Link_shut_down_p_fixed_upper:
     place, an explicit row as PyPSA writes it: one where the build is not
     modular, and the fixed build's whole count of modules where it is
   dims: [scenario, snapshot, link]
-  where: Link_committable AND NOT (Link_p_nom_extendable AND Link_p_nom_mod > 0) AND Link_active
+  where: Link_committed AND NOT (Link_p_nom_extendable AND Link_p_nom_mod > 0)
   expression: Link_shut_down <= Link_modules_installed
 ```
 
 ```math
-\mathit{dn}^{f}_{\xi,t,l} \le \mathrm{N}^{f,\mathrm{fix}}_{\xi,l} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{com}^{f}_{l} \wedge \neg \left( \mathrm{ext}^{f}_{l} \wedge \mathrm{f}^{\mathrm{mod}}_{l} > 0 \right) \wedge \mathrm{on}^{f}_{t,l}
+\mathit{dn}^{f}_{\xi,t,l} \le \mathrm{N}^{f,\mathrm{fix}}_{\xi,l} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{on}^{f,\mathrm{com}}_{t,l} \wedge \neg \left( \mathrm{ext}^{f}_{l} \wedge \mathrm{f}^{\mathrm{mod}}_{l} > 0 \right)
 ```
 
 ### `Link-status-p_nom-variable-upper`
@@ -7365,12 +7362,12 @@ Link_shut_down_p_fixed_upper:
 Link_status_p_nom_variable_upper:
   description: "`Link-status-p_nom-variable-upper` — a modular link is on only where a module is built"
   dims: [scenario, snapshot, link]
-  where: Link_committable AND Link_p_nom_extendable AND Link_p_nom_mod > 0 AND Link_active
+  where: Link_committed AND Link_p_nom_extendable AND Link_p_nom_mod > 0
   expression: Link_status <= Link_n_mod
 ```
 
 ```math
-u^{f}_{\xi,t,l} \le N^{f}_{l} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{com}^{f}_{l} \wedge \mathrm{ext}^{f}_{l} \wedge \mathrm{f}^{\mathrm{mod}}_{l} > 0 \wedge \mathrm{on}^{f}_{t,l}
+u^{f}_{\xi,t,l} \le N^{f}_{l} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{on}^{f,\mathrm{com}}_{t,l} \wedge \mathrm{ext}^{f}_{l} \wedge \mathrm{f}^{\mathrm{mod}}_{l} > 0
 ```
 
 ### `Link-start_up-p_nom-variable-upper`
@@ -7381,12 +7378,12 @@ u^{f}_{\xi,t,l} \le N^{f}_{l} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\
 Link_start_up_p_nom_variable_upper:
   description: "`Link-start_up-p_nom-variable-upper` — a modular link starts only where a module is built"
   dims: [scenario, snapshot, link]
-  where: Link_committable AND Link_p_nom_extendable AND Link_p_nom_mod > 0 AND Link_active
+  where: Link_committed AND Link_p_nom_extendable AND Link_p_nom_mod > 0
   expression: Link_start_up <= Link_n_mod
 ```
 
 ```math
-\mathit{up}^{f}_{\xi,t,l} \le N^{f}_{l} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{com}^{f}_{l} \wedge \mathrm{ext}^{f}_{l} \wedge \mathrm{f}^{\mathrm{mod}}_{l} > 0 \wedge \mathrm{on}^{f}_{t,l}
+\mathit{up}^{f}_{\xi,t,l} \le N^{f}_{l} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{on}^{f,\mathrm{com}}_{t,l} \wedge \mathrm{ext}^{f}_{l} \wedge \mathrm{f}^{\mathrm{mod}}_{l} > 0
 ```
 
 ### `Link-shut_down-p_nom-variable-upper`
@@ -7397,12 +7394,12 @@ Link_start_up_p_nom_variable_upper:
 Link_shut_down_p_nom_variable_upper:
   description: "`Link-shut_down-p_nom-variable-upper` — a modular link stops only where a module is built"
   dims: [scenario, snapshot, link]
-  where: Link_committable AND Link_p_nom_extendable AND Link_p_nom_mod > 0 AND Link_active
+  where: Link_committed AND Link_p_nom_extendable AND Link_p_nom_mod > 0
   expression: Link_shut_down <= Link_n_mod
 ```
 
 ```math
-\mathit{dn}^{f}_{\xi,t,l} \le N^{f}_{l} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{com}^{f}_{l} \wedge \mathrm{ext}^{f}_{l} \wedge \mathrm{f}^{\mathrm{mod}}_{l} > 0 \wedge \mathrm{on}^{f}_{t,l}
+\mathit{dn}^{f}_{\xi,t,l} \le N^{f}_{l} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{on}^{f,\mathrm{com}}_{t,l} \wedge \mathrm{ext}^{f}_{l} \wedge \mathrm{f}^{\mathrm{mod}}_{l} > 0
 ```
 
 ### `Link-maint-event-count`
@@ -7466,12 +7463,12 @@ Link_maintcap_upper:
     `Link-maintcap_upper` — the build taken off is at most the chosen build in
     maintenance, and at most the build less its floor out of it
   dims: [scenario, snapshot, link]
-  where: Link_maintainable AND Link_p_nom_extendable AND NOT (Link_committable AND Link_p_nom_mod > 0) AND Link_active
+  where: Link_maint_ext
   expression: Link_maintenance_capacity <= Link_p_nom_ext - Link_p_nom_min * (1 - Link_maintenance)
 ```
 
 ```math
-\mu^{f,\mathrm{nom}}_{\xi,t,l} \le F_{l} - \underline{\mathrm{f}}^{\mathrm{nom}}_{\xi,l} \cdot \left( 1 - \mu^{f}_{\xi,t,l} \right) \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{mnt}^{f}_{l} \wedge \mathrm{ext}^{f}_{l} \wedge \neg \left( \mathrm{com}^{f}_{l} \wedge \mathrm{f}^{\mathrm{mod}}_{l} > 0 \right) \wedge \mathrm{on}^{f}_{t,l}
+\mu^{f,\mathrm{nom}}_{\xi,t,l} \le F_{l} - \underline{\mathrm{f}}^{\mathrm{nom}}_{\xi,l} \cdot \left( 1 - \mu^{f}_{\xi,t,l} \right) \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{on}^{f,\mathrm{mnt,ext}}_{t,l}
 ```
 
 ### `Link-maintcap_upper_nommax`
@@ -7482,12 +7479,12 @@ Link_maintcap_upper:
 Link_maintcap_upper_nommax:
   description: "`Link-maintcap_upper_nommax` — out of maintenance, no build is taken off"
   dims: [scenario, snapshot, link]
-  where: Link_maintainable AND Link_p_nom_extendable AND NOT (Link_committable AND Link_p_nom_mod > 0) AND Link_active
+  where: Link_maint_ext
   expression: Link_maintenance_capacity <= Link_p_nom_max * Link_maintenance
 ```
 
 ```math
-\mu^{f,\mathrm{nom}}_{\xi,t,l} \le \overline{\mathrm{f}}^{\mathrm{nom}}_{\xi,l} \cdot \mu^{f}_{\xi,t,l} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{mnt}^{f}_{l} \wedge \mathrm{ext}^{f}_{l} \wedge \neg \left( \mathrm{com}^{f}_{l} \wedge \mathrm{f}^{\mathrm{mod}}_{l} > 0 \right) \wedge \mathrm{on}^{f}_{t,l}
+\mu^{f,\mathrm{nom}}_{\xi,t,l} \le \overline{\mathrm{f}}^{\mathrm{nom}}_{\xi,l} \cdot \mu^{f}_{\xi,t,l} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{on}^{f,\mathrm{mnt,ext}}_{t,l}
 ```
 
 ### `Link-maintcap_lower_nommax`
@@ -7498,12 +7495,12 @@ Link_maintcap_upper_nommax:
 Link_maintcap_lower_nommax:
   description: "`Link-maintcap_lower_nommax` — in maintenance, the whole chosen build is taken off"
   dims: [scenario, snapshot, link]
-  where: Link_maintainable AND Link_p_nom_extendable AND NOT (Link_committable AND Link_p_nom_mod > 0) AND Link_active
+  where: Link_maint_ext
   expression: Link_maintenance_capacity >= Link_p_nom_ext - Link_p_nom_max * (1 - Link_maintenance)
 ```
 
 ```math
-\mu^{f,\mathrm{nom}}_{\xi,t,l} \ge F_{l} - \overline{\mathrm{f}}^{\mathrm{nom}}_{\xi,l} \cdot \left( 1 - \mu^{f}_{\xi,t,l} \right) \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{mnt}^{f}_{l} \wedge \mathrm{ext}^{f}_{l} \wedge \neg \left( \mathrm{com}^{f}_{l} \wedge \mathrm{f}^{\mathrm{mod}}_{l} > 0 \right) \wedge \mathrm{on}^{f}_{t,l}
+\mu^{f,\mathrm{nom}}_{\xi,t,l} \ge F_{l} - \overline{\mathrm{f}}^{\mathrm{nom}}_{\xi,l} \cdot \left( 1 - \mu^{f}_{\xi,t,l} \right) \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{on}^{f,\mathrm{mnt,ext}}_{t,l}
 ```
 
 ### `Link-maintcap_lower_nommin`
@@ -7514,12 +7511,12 @@ Link_maintcap_lower_nommax:
 Link_maintcap_lower_nommin:
   description: "`Link-maintcap_lower_nommin` — in maintenance, at least the floor of the build is taken off"
   dims: [scenario, snapshot, link]
-  where: Link_maintainable AND Link_p_nom_extendable AND NOT (Link_committable AND Link_p_nom_mod > 0) AND Link_active AND Link_p_nom_min > 0
+  where: Link_maint_ext AND Link_p_nom_min > 0
   expression: Link_maintenance_capacity >= Link_p_nom_min * Link_maintenance
 ```
 
 ```math
-\mu^{f,\mathrm{nom}}_{\xi,t,l} \ge \underline{\mathrm{f}}^{\mathrm{nom}}_{\xi,l} \cdot \mu^{f}_{\xi,t,l} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{mnt}^{f}_{l} \wedge \mathrm{ext}^{f}_{l} \wedge \neg \left( \mathrm{com}^{f}_{l} \wedge \mathrm{f}^{\mathrm{mod}}_{l} > 0 \right) \wedge \mathrm{on}^{f}_{t,l} \wedge \underline{\mathrm{f}}^{\mathrm{nom}}_{\xi,l} > 0
+\mu^{f,\mathrm{nom}}_{\xi,t,l} \ge \underline{\mathrm{f}}^{\mathrm{nom}}_{\xi,l} \cdot \mu^{f}_{\xi,t,l} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{on}^{f,\mathrm{mnt,ext}}_{t,l} \wedge \underline{\mathrm{f}}^{\mathrm{nom}}_{\xi,l} > 0
 ```
 
 ### `Link-maint-status-le-status`
@@ -7530,12 +7527,12 @@ Link_maintcap_lower_nommin:
 Link_maint_status_le_status:
   description: "`Link-maint-status-le-status` — the status in maintenance is at most the status"
   dims: [scenario, snapshot, link]
-  where: Link_maintainable AND Link_committable AND NOT Link_p_nom_extendable AND NOT (Link_p_nom_mod > 0) AND Link_active
+  where: Link_maintainable AND Link_committed AND NOT Link_p_nom_extendable AND NOT (Link_p_nom_mod > 0)
   expression: Link_maintenance_status <= Link_status
 ```
 
 ```math
-\mu^{f,u}_{\xi,t,l} \le u^{f}_{\xi,t,l} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{mnt}^{f}_{l} \wedge \mathrm{com}^{f}_{l} \wedge \neg \mathrm{ext}^{f}_{l} \wedge \neg \left( \mathrm{f}^{\mathrm{mod}}_{l} > 0 \right) \wedge \mathrm{on}^{f}_{t,l}
+\mu^{f,u}_{\xi,t,l} \le u^{f}_{\xi,t,l} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{mnt}^{f}_{l} \wedge \mathrm{on}^{f,\mathrm{com}}_{t,l} \wedge \neg \mathrm{ext}^{f}_{l} \wedge \neg \left( \mathrm{f}^{\mathrm{mod}}_{l} > 0 \right)
 ```
 
 ### `Link-maint-status-le-maint`
@@ -7546,12 +7543,12 @@ Link_maint_status_le_status:
 Link_maint_status_le_maint:
   description: "`Link-maint-status-le-maint` — out of maintenance, the status in maintenance is zero"
   dims: [scenario, snapshot, link]
-  where: Link_maintainable AND Link_committable AND NOT Link_p_nom_extendable AND NOT (Link_p_nom_mod > 0) AND Link_active
+  where: Link_maintainable AND Link_committed AND NOT Link_p_nom_extendable AND NOT (Link_p_nom_mod > 0)
   expression: Link_maintenance_status <= Link_maintenance
 ```
 
 ```math
-\mu^{f,u}_{\xi,t,l} \le \mu^{f}_{\xi,t,l} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{mnt}^{f}_{l} \wedge \mathrm{com}^{f}_{l} \wedge \neg \mathrm{ext}^{f}_{l} \wedge \neg \left( \mathrm{f}^{\mathrm{mod}}_{l} > 0 \right) \wedge \mathrm{on}^{f}_{t,l}
+\mu^{f,u}_{\xi,t,l} \le \mu^{f}_{\xi,t,l} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{mnt}^{f}_{l} \wedge \mathrm{on}^{f,\mathrm{com}}_{t,l} \wedge \neg \mathrm{ext}^{f}_{l} \wedge \neg \left( \mathrm{f}^{\mathrm{mod}}_{l} > 0 \right)
 ```
 
 ### `Link-maint-status-lb`
@@ -7562,12 +7559,12 @@ Link_maint_status_le_maint:
 Link_maint_status_lb:
   description: "`Link-maint-status-lb` — on and in maintenance, the status in maintenance is one"
   dims: [scenario, snapshot, link]
-  where: Link_maintainable AND Link_committable AND NOT Link_p_nom_extendable AND NOT (Link_p_nom_mod > 0) AND Link_active
+  where: Link_maintainable AND Link_committed AND NOT Link_p_nom_extendable AND NOT (Link_p_nom_mod > 0)
   expression: Link_maintenance_status >= Link_status + Link_maintenance - 1
 ```
 
 ```math
-\mu^{f,u}_{\xi,t,l} \ge u^{f}_{\xi,t,l} + \mu^{f}_{\xi,t,l} - 1 \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{mnt}^{f}_{l} \wedge \mathrm{com}^{f}_{l} \wedge \neg \mathrm{ext}^{f}_{l} \wedge \neg \left( \mathrm{f}^{\mathrm{mod}}_{l} > 0 \right) \wedge \mathrm{on}^{f}_{t,l}
+\mu^{f,u}_{\xi,t,l} \ge u^{f}_{\xi,t,l} + \mu^{f}_{\xi,t,l} - 1 \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{mnt}^{f}_{l} \wedge \mathrm{on}^{f,\mathrm{com}}_{t,l} \wedge \neg \mathrm{ext}^{f}_{l} \wedge \neg \left( \mathrm{f}^{\mathrm{mod}}_{l} > 0 \right)
 ```
 
 ### `Link-maint-modstatus-le-status`
@@ -7578,12 +7575,12 @@ Link_maint_status_lb:
 Link_maint_modstatus_le_status:
   description: "`Link-maint-modstatus-le-status` — the modules on in maintenance are at most the modules on"
   dims: [scenario, snapshot, link]
-  where: Link_maintainable AND Link_committable AND Link_p_nom_mod > 0 AND Link_active
+  where: Link_maintainable AND Link_committed AND Link_p_nom_mod > 0
   expression: Link_maintenance_status <= Link_status
 ```
 
 ```math
-\mu^{f,u}_{\xi,t,l} \le u^{f}_{\xi,t,l} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{mnt}^{f}_{l} \wedge \mathrm{com}^{f}_{l} \wedge \mathrm{f}^{\mathrm{mod}}_{l} > 0 \wedge \mathrm{on}^{f}_{t,l}
+\mu^{f,u}_{\xi,t,l} \le u^{f}_{\xi,t,l} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{mnt}^{f}_{l} \wedge \mathrm{on}^{f,\mathrm{com}}_{t,l} \wedge \mathrm{f}^{\mathrm{mod}}_{l} > 0
 ```
 
 ### `Link-maint-modstatus-le-maint`
@@ -7596,12 +7593,12 @@ Link_maint_modstatus_le_maint:
     `Link-maint-modstatus-le-maint` — out of maintenance, no module is on in
     maintenance; in it, at most the modules the build cap holds
   dims: [scenario, snapshot, link]
-  where: Link_maintainable AND Link_committable AND Link_p_nom_mod > 0 AND Link_active
+  where: Link_maintainable AND Link_committed AND Link_p_nom_mod > 0
   expression: Link_maintenance_status <= Link_p_nom_max / Link_p_nom_mod * Link_maintenance
 ```
 
 ```math
-\mu^{f,u}_{\xi,t,l} \le \frac{\overline{\mathrm{f}}^{\mathrm{nom}}_{\xi,l}}{\mathrm{f}^{\mathrm{mod}}_{l}} \cdot \mu^{f}_{\xi,t,l} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{mnt}^{f}_{l} \wedge \mathrm{com}^{f}_{l} \wedge \mathrm{f}^{\mathrm{mod}}_{l} > 0 \wedge \mathrm{on}^{f}_{t,l}
+\mu^{f,u}_{\xi,t,l} \le \frac{\overline{\mathrm{f}}^{\mathrm{nom}}_{\xi,l}}{\mathrm{f}^{\mathrm{mod}}_{l}} \cdot \mu^{f}_{\xi,t,l} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{mnt}^{f}_{l} \wedge \mathrm{on}^{f,\mathrm{com}}_{t,l} \wedge \mathrm{f}^{\mathrm{mod}}_{l} > 0
 ```
 
 ### `Link-maint-modstatus-lb`
@@ -7612,12 +7609,12 @@ Link_maint_modstatus_le_maint:
 Link_maint_modstatus_lb:
   description: "`Link-maint-modstatus-lb` — in maintenance, every module on is on in maintenance"
   dims: [scenario, snapshot, link]
-  where: Link_maintainable AND Link_committable AND Link_p_nom_mod > 0 AND Link_active
+  where: Link_maintainable AND Link_committed AND Link_p_nom_mod > 0
   expression: Link_maintenance_status >= Link_status - Link_p_nom_max / Link_p_nom_mod * (1 - Link_maintenance)
 ```
 
 ```math
-\mu^{f,u}_{\xi,t,l} \ge u^{f}_{\xi,t,l} - \frac{\overline{\mathrm{f}}^{\mathrm{nom}}_{\xi,l}}{\mathrm{f}^{\mathrm{mod}}_{l}} \cdot \left( 1 - \mu^{f}_{\xi,t,l} \right) \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{mnt}^{f}_{l} \wedge \mathrm{com}^{f}_{l} \wedge \mathrm{f}^{\mathrm{mod}}_{l} > 0 \wedge \mathrm{on}^{f}_{t,l}
+\mu^{f,u}_{\xi,t,l} \ge u^{f}_{\xi,t,l} - \frac{\overline{\mathrm{f}}^{\mathrm{nom}}_{\xi,l}}{\mathrm{f}^{\mathrm{mod}}_{l}} \cdot \left( 1 - \mu^{f}_{\xi,t,l} \right) \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{mnt}^{f}_{l} \wedge \mathrm{on}^{f,\mathrm{com}}_{t,l} \wedge \mathrm{f}^{\mathrm{mod}}_{l} > 0
 ```
 
 ### `Process-com-p-lower`
@@ -7628,12 +7625,12 @@ Link_maint_modstatus_lb:
 Process_com_p_lower:
   description: "`Process-com-p-lower` — a committed process runs at least its minimum; off, at least nothing"
   dims: [scenario, snapshot, process]
-  where: Process_committable AND not Process_p_nom_extendable AND NOT (Process_p_nom_mod > 0) AND Process_active
+  where: Process_committed AND NOT Process_p_nom_extendable AND NOT (Process_p_nom_mod > 0)
   expression: Process_p >= Process_p_min_pu * Process_p_nom * (Process_status - Process_maintenance_pu * Process_maintenance_status)
 ```
 
 ```math
-z_{\xi,t,j} \ge \underline{\mathrm{z}}_{\xi,t,j} \cdot \mathrm{z}^{\mathrm{nom}}_{\xi,j} \cdot \left( u^{z}_{\xi,t,j} - \gamma^{z}_{\xi,j} \cdot \mu^{z,u}_{\xi,t,j} \right) \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{com}^{z}_{j} \wedge \neg \mathrm{ext}^{z}_{j} \wedge \neg \left( \mathrm{z}^{\mathrm{mod}}_{j} > 0 \right) \wedge \mathrm{on}^{z}_{t,j}
+z_{\xi,t,j} \ge \underline{\mathrm{z}}_{\xi,t,j} \cdot \mathrm{z}^{\mathrm{nom}}_{\xi,j} \cdot \left( u^{z}_{\xi,t,j} - \gamma^{z}_{\xi,j} \cdot \mu^{z,u}_{\xi,t,j} \right) \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{on}^{z,\mathrm{com}}_{t,j} \wedge \neg \mathrm{ext}^{z}_{j} \wedge \neg \left( \mathrm{z}^{\mathrm{mod}}_{j} > 0 \right)
 ```
 
 ### `Process-com-p-upper`
@@ -7644,12 +7641,12 @@ z_{\xi,t,j} \ge \underline{\mathrm{z}}_{\xi,t,j} \cdot \mathrm{z}^{\mathrm{nom}}
 Process_com_p_upper:
   description: "`Process-com-p-upper` — a committed process runs at most what is available; off, at most nothing"
   dims: [scenario, snapshot, process]
-  where: Process_committable AND not Process_p_nom_extendable AND NOT (Process_p_nom_mod > 0) AND Process_active
+  where: Process_committed AND NOT Process_p_nom_extendable AND NOT (Process_p_nom_mod > 0)
   expression: Process_p <= Process_p_max_pu * Process_p_nom * (Process_status - Process_maintenance_pu * Process_maintenance_status)
 ```
 
 ```math
-z_{\xi,t,j} \le \overline{\mathrm{z}}_{\xi,t,j} \cdot \mathrm{z}^{\mathrm{nom}}_{\xi,j} \cdot \left( u^{z}_{\xi,t,j} - \gamma^{z}_{\xi,j} \cdot \mu^{z,u}_{\xi,t,j} \right) \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{com}^{z}_{j} \wedge \neg \mathrm{ext}^{z}_{j} \wedge \neg \left( \mathrm{z}^{\mathrm{mod}}_{j} > 0 \right) \wedge \mathrm{on}^{z}_{t,j}
+z_{\xi,t,j} \le \overline{\mathrm{z}}_{\xi,t,j} \cdot \mathrm{z}^{\mathrm{nom}}_{\xi,j} \cdot \left( u^{z}_{\xi,t,j} - \gamma^{z}_{\xi,j} \cdot \mu^{z,u}_{\xi,t,j} \right) \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{on}^{z,\mathrm{com}}_{t,j} \wedge \neg \mathrm{ext}^{z}_{j} \wedge \neg \left( \mathrm{z}^{\mathrm{mod}}_{j} > 0 \right)
 ```
 
 ### `Process-com-transition-start-up`
@@ -7660,12 +7657,12 @@ z_{\xi,t,j} \le \overline{\mathrm{z}}_{\xi,t,j} \cdot \mathrm{z}^{\mathrm{nom}}_
 Process_com_transition_start_up:
   description: "`Process-com-transition-start-up` — turning on is a start, counted against the state the process carried into the snapshot"
   dims: [scenario, snapshot, process]
-  where: Process_committable AND Process_active
+  where: Process_committed
   expression: Process_start_up >= Process_status - Process_previous_status
 ```
 
 ```math
-\mathit{up}^{z}_{\xi,t,j} \ge u^{z}_{\xi,t,j} - \overleftarrow{u}^{z}_{\xi,t,j} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{com}^{z}_{j} \wedge \mathrm{on}^{z}_{t,j}
+\mathit{up}^{z}_{\xi,t,j} \ge u^{z}_{\xi,t,j} - \overleftarrow{u}^{z}_{\xi,t,j} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{on}^{z,\mathrm{com}}_{t,j}
 ```
 
 ### `Process-com-transition-shut-down`
@@ -7676,12 +7673,12 @@ Process_com_transition_start_up:
 Process_com_transition_shut_down:
   description: "`Process-com-transition-shut-down` — turning off is a stop, counted against the state the process carried into the snapshot"
   dims: [scenario, snapshot, process]
-  where: Process_committable AND Process_active
+  where: Process_committed
   expression: Process_shut_down >= Process_previous_status - Process_status
 ```
 
 ```math
-\mathit{dn}^{z}_{\xi,t,j} \ge \overleftarrow{u}^{z}_{\xi,t,j} - u^{z}_{\xi,t,j} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{com}^{z}_{j} \wedge \mathrm{on}^{z}_{t,j}
+\mathit{dn}^{z}_{\xi,t,j} \ge \overleftarrow{u}^{z}_{\xi,t,j} - u^{z}_{\xi,t,j} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{on}^{z,\mathrm{com}}_{t,j}
 ```
 
 ### `Process-com-up-time`
@@ -7695,12 +7692,12 @@ Process_com_up_time:
     is still on. The first snapshot's share of the window is the brought-in
     up time's, which the must-stay-up mask carries
   dims: [scenario, snapshot, process]
-  where: Process_committable AND Process_min_up_time > 0 AND position(snapshot) > 0 AND Process_active
+  where: Process_committed AND Process_min_up_time > 0 AND position(snapshot) > 0
   expression: sum_back(Process_start_up, along=snapshot, window=Process_min_up_time) <= Process_status
 ```
 
 ```math
-\sum_{t' \in \mathcal{T} \,:\, 0 \le t - t' < \mathrm{UT}^{z}} \mathit{up}^{z}_{\xi,t',j} \le u^{z}_{\xi,t,j} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{com}^{z}_{j} \wedge \mathrm{UT}^{z}_{\xi,j} > 0 \wedge \mathrm{pos}(t) > 0 \wedge \mathrm{on}^{z}_{t,j}
+\sum_{t' \in \mathcal{T} \,:\, 0 \le t - t' < \mathrm{UT}^{z}} \mathit{up}^{z}_{\xi,t',j} \le u^{z}_{\xi,t,j} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{on}^{z,\mathrm{com}}_{t,j} \wedge \mathrm{UT}^{z}_{\xi,j} > 0 \wedge \mathrm{pos}(t) > 0
 ```
 
 ### `Process-com-down-time`
@@ -7714,12 +7711,12 @@ Process_com_down_time:
     time is still off. The first snapshot's share of the window is the
     brought-in down time's, which the must-stay-down mask carries
   dims: [scenario, snapshot, process]
-  where: Process_committable AND Process_min_down_time > 0 AND position(snapshot) > 0 AND Process_active
+  where: Process_committed AND Process_min_down_time > 0 AND position(snapshot) > 0
   expression: sum_back(Process_shut_down, along=snapshot, window=Process_min_down_time) <= 1 - Process_status
 ```
 
 ```math
-\sum_{t' \in \mathcal{T} \,:\, 0 \le t - t' < \mathrm{DT}^{z}} \mathit{dn}^{z}_{\xi,t',j} \le 1 - u^{z}_{\xi,t,j} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{com}^{z}_{j} \wedge \mathrm{DT}^{z}_{\xi,j} > 0 \wedge \mathrm{pos}(t) > 0 \wedge \mathrm{on}^{z}_{t,j}
+\sum_{t' \in \mathcal{T} \,:\, 0 \le t - t' < \mathrm{DT}^{z}} \mathit{dn}^{z}_{\xi,t',j} \le 1 - u^{z}_{\xi,t,j} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{on}^{z,\mathrm{com}}_{t,j} \wedge \mathrm{DT}^{z}_{\xi,j} > 0 \wedge \mathrm{pos}(t) > 0
 ```
 
 ### `Process-com-status-min_up_time_must_stay_up`
@@ -7730,12 +7727,12 @@ Process_com_down_time:
 Process_com_status_must_stay_up:
   description: "`Process-com-status-min_up_time_must_stay_up` — a process still serving the up time it brought in stays on"
   dims: [scenario, snapshot, process]
-  where: Process_committable AND Process_must_stay_up AND Process_active
+  where: Process_committed AND Process_must_stay_up
   expression: Process_status == 1
 ```
 
 ```math
-u^{z}_{\xi,t,j} = 1 \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{com}^{z}_{j} \wedge \mathrm{hold}^{z}_{\xi,t,j} \wedge \mathrm{on}^{z}_{t,j}
+u^{z}_{\xi,t,j} = 1 \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{on}^{z,\mathrm{com}}_{t,j} \wedge \mathrm{hold}^{z}_{\xi,t,j}
 ```
 
 ### `Process-com-status-min_down_time_must_stay_up`
@@ -7748,12 +7745,12 @@ Process_com_status_must_stay_down:
     `Process-com-status-min_down_time_must_stay_up` — a process still serving
     the down time it brought in stays off; PyPSA names the row `_must_stay_up`
   dims: [scenario, snapshot, process]
-  where: Process_committable AND Process_must_stay_down AND Process_active
+  where: Process_committed AND Process_must_stay_down
   expression: Process_status == 0
 ```
 
 ```math
-u^{z}_{\xi,t,j} = 0 \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{com}^{z}_{j} \wedge \mathrm{rest}^{z}_{\xi,t,j} \wedge \mathrm{on}^{z}_{t,j}
+u^{z}_{\xi,t,j} = 0 \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{on}^{z,\mathrm{com}}_{t,j} \wedge \mathrm{rest}^{z}_{\xi,t,j}
 ```
 
 ### `Process-p-ramp_limit_up-run-bigM`
@@ -7767,11 +7764,7 @@ Process_p_ramp_limit_up_run_big_m:
     raises internal power no faster than its limit of the chosen build; the big M
     releases the row in the snapshot it turns on
   dims: [scenario, snapshot, process]
-  where: >-
-    Process_committable AND Process_p_nom_extendable AND NOT (Process_p_nom_mod > 0)
-    AND (Process_ramp_limit_up OR Process_ramp_limit_start_up)
-    AND (position(snapshot, within=snapshot_period[period]) > 0 OR (position(snapshot) == 0 AND (Process_status_initial == 0 OR Process_p_init)))
-    AND Process_active
+  where: Process_com_ext AND (Process_ramp_limit_up OR Process_ramp_limit_start_up) AND Process_ramps_from_previous
   expression: >-
     Process_p - Process_previous_p <=
     Process_ramp_up_rate * Process_p_nom_ext
@@ -7779,7 +7772,7 @@ Process_p_ramp_limit_up_run_big_m:
 ```
 
 ```math
-z_{\xi,t,j} - \overleftarrow{z}_{\xi,t,j} \le \widetilde{\mathrm{ru}}^{z}_{\xi,t,j} \cdot Z_{j} + \mathrm{M}^{z}_{\xi,j} - \mathrm{M}^{z}_{\xi,j} \cdot \overleftarrow{u}^{z}_{\xi,t,j} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{com}^{z}_{j} \wedge \mathrm{ext}^{z}_{j} \wedge \neg \left( \mathrm{z}^{\mathrm{mod}}_{j} > 0 \right) \wedge \left( \mathrm{ru}^{z}_{\xi,t,j} \text{ is defined} \vee \mathrm{ru}^{z,\mathrm{up}}_{\xi,j} \text{ is defined} \right) \wedge \left( \mathrm{pos}_{\mathrm{snapshot\_period}(t)}(t) > 0 \vee \mathrm{pos}(t) = 0 \wedge \left( \mathrm{u}^{z,0}_{\xi,j} = 0 \vee \mathrm{z}^{0}_{\xi,j} \text{ is defined} \right) \right) \wedge \mathrm{on}^{z}_{t,j}
+z_{\xi,t,j} - \overleftarrow{z}_{\xi,t,j} \le \widetilde{\mathrm{ru}}^{z}_{\xi,t,j} \cdot Z_{j} + \mathrm{M}^{z}_{\xi,j} - \mathrm{M}^{z}_{\xi,j} \cdot \overleftarrow{u}^{z}_{\xi,t,j} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{on}^{z,\mathrm{com,ext}}_{t,j} \wedge \left( \mathrm{ru}^{z}_{\xi,t,j} \text{ is defined} \vee \mathrm{ru}^{z,\mathrm{up}}_{\xi,j} \text{ is defined} \right) \wedge \mathrm{prev}^{z}_{\xi,t,j}
 ```
 
 ### `Process-p-ramp_limit_up-start-bigM`
@@ -7793,11 +7786,7 @@ Process_p_ramp_limit_up_start_big_m:
     committed extendable process ramps no further than its start-up ramp of
     the chosen build; the big M releases the row everywhere else
   dims: [scenario, snapshot, process]
-  where: >-
-    Process_committable AND Process_p_nom_extendable AND NOT (Process_p_nom_mod > 0)
-    AND (Process_ramp_limit_up OR Process_ramp_limit_start_up)
-    AND (position(snapshot, within=snapshot_period[period]) > 0 OR (position(snapshot) == 0 AND (Process_status_initial == 0 OR Process_p_init)))
-    AND Process_active
+  where: Process_com_ext AND (Process_ramp_limit_up OR Process_ramp_limit_start_up) AND Process_ramps_from_previous
   expression: >-
     Process_p - Process_previous_p <=
     Process_start_up_rate * Process_p_nom_ext
@@ -7805,7 +7794,7 @@ Process_p_ramp_limit_up_start_big_m:
 ```
 
 ```math
-z_{\xi,t,j} - \overleftarrow{z}_{\xi,t,j} \le \widetilde{\mathrm{ru}}^{z,\mathrm{up}}_{\xi,j} \cdot Z_{j} + \mathrm{M}^{z}_{\xi,j} - \mathrm{M}^{z}_{\xi,j} \cdot \mathit{up}^{z}_{\xi,t,j} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{com}^{z}_{j} \wedge \mathrm{ext}^{z}_{j} \wedge \neg \left( \mathrm{z}^{\mathrm{mod}}_{j} > 0 \right) \wedge \left( \mathrm{ru}^{z}_{\xi,t,j} \text{ is defined} \vee \mathrm{ru}^{z,\mathrm{up}}_{\xi,j} \text{ is defined} \right) \wedge \left( \mathrm{pos}_{\mathrm{snapshot\_period}(t)}(t) > 0 \vee \mathrm{pos}(t) = 0 \wedge \left( \mathrm{u}^{z,0}_{\xi,j} = 0 \vee \mathrm{z}^{0}_{\xi,j} \text{ is defined} \right) \right) \wedge \mathrm{on}^{z}_{t,j}
+z_{\xi,t,j} - \overleftarrow{z}_{\xi,t,j} \le \widetilde{\mathrm{ru}}^{z,\mathrm{up}}_{\xi,j} \cdot Z_{j} + \mathrm{M}^{z}_{\xi,j} - \mathrm{M}^{z}_{\xi,j} \cdot \mathit{up}^{z}_{\xi,t,j} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{on}^{z,\mathrm{com,ext}}_{t,j} \wedge \left( \mathrm{ru}^{z}_{\xi,t,j} \text{ is defined} \vee \mathrm{ru}^{z,\mathrm{up}}_{\xi,j} \text{ is defined} \right) \wedge \mathrm{prev}^{z}_{\xi,t,j}
 ```
 
 ### `Process-p-ramp_limit_down-run-bigM`
@@ -7820,10 +7809,9 @@ Process_p_ramp_limit_down_run_big_m:
     releases the row in the snapshot it turns off
   dims: [scenario, snapshot, process]
   where: >-
-    Process_committable AND Process_p_nom_extendable AND NOT (Process_p_nom_mod > 0)
+    Process_com_ext
     AND (Process_ramp_limit_down OR Process_ramp_limit_shut_down)
-    AND (position(snapshot, within=snapshot_period[period]) > 0 OR (position(snapshot) == 0 AND (Process_status_initial == 0 OR Process_p_init)))
-    AND Process_active
+    AND Process_ramps_from_previous
   expression: >-
     Process_previous_p - Process_p <=
     Process_ramp_down_rate * Process_p_nom_ext
@@ -7831,7 +7819,7 @@ Process_p_ramp_limit_down_run_big_m:
 ```
 
 ```math
-\overleftarrow{z}_{\xi,t,j} - z_{\xi,t,j} \le \widetilde{\mathrm{rd}}^{z}_{\xi,t,j} \cdot Z_{j} + \mathrm{M}^{z}_{\xi,j} - \mathrm{M}^{z}_{\xi,j} \cdot u^{z}_{\xi,t,j} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{com}^{z}_{j} \wedge \mathrm{ext}^{z}_{j} \wedge \neg \left( \mathrm{z}^{\mathrm{mod}}_{j} > 0 \right) \wedge \left( \mathrm{rd}^{z}_{\xi,t,j} \text{ is defined} \vee \mathrm{rd}^{z,\mathrm{dn}}_{\xi,j} \text{ is defined} \right) \wedge \left( \mathrm{pos}_{\mathrm{snapshot\_period}(t)}(t) > 0 \vee \mathrm{pos}(t) = 0 \wedge \left( \mathrm{u}^{z,0}_{\xi,j} = 0 \vee \mathrm{z}^{0}_{\xi,j} \text{ is defined} \right) \right) \wedge \mathrm{on}^{z}_{t,j}
+\overleftarrow{z}_{\xi,t,j} - z_{\xi,t,j} \le \widetilde{\mathrm{rd}}^{z}_{\xi,t,j} \cdot Z_{j} + \mathrm{M}^{z}_{\xi,j} - \mathrm{M}^{z}_{\xi,j} \cdot u^{z}_{\xi,t,j} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{on}^{z,\mathrm{com,ext}}_{t,j} \wedge \left( \mathrm{rd}^{z}_{\xi,t,j} \text{ is defined} \vee \mathrm{rd}^{z,\mathrm{dn}}_{\xi,j} \text{ is defined} \right) \wedge \mathrm{prev}^{z}_{\xi,t,j}
 ```
 
 ### `Process-p-ramp_limit_down-shut-bigM`
@@ -7846,10 +7834,9 @@ Process_p_ramp_limit_down_shut_big_m:
     the chosen build; the big M releases the row everywhere else
   dims: [scenario, snapshot, process]
   where: >-
-    Process_committable AND Process_p_nom_extendable AND NOT (Process_p_nom_mod > 0)
+    Process_com_ext
     AND (Process_ramp_limit_down OR Process_ramp_limit_shut_down)
-    AND (position(snapshot, within=snapshot_period[period]) > 0 OR (position(snapshot) == 0 AND (Process_status_initial == 0 OR Process_p_init)))
-    AND Process_active
+    AND Process_ramps_from_previous
   expression: >-
     Process_previous_p - Process_p <=
     Process_shut_down_rate * Process_p_nom_ext
@@ -7857,7 +7844,7 @@ Process_p_ramp_limit_down_shut_big_m:
 ```
 
 ```math
-\overleftarrow{z}_{\xi,t,j} - z_{\xi,t,j} \le \widetilde{\mathrm{rd}}^{z,\mathrm{dn}}_{\xi,j} \cdot Z_{j} + \mathrm{M}^{z}_{\xi,j} - \mathrm{M}^{z}_{\xi,j} \cdot \mathit{dn}^{z}_{\xi,t,j} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{com}^{z}_{j} \wedge \mathrm{ext}^{z}_{j} \wedge \neg \left( \mathrm{z}^{\mathrm{mod}}_{j} > 0 \right) \wedge \left( \mathrm{rd}^{z}_{\xi,t,j} \text{ is defined} \vee \mathrm{rd}^{z,\mathrm{dn}}_{\xi,j} \text{ is defined} \right) \wedge \left( \mathrm{pos}_{\mathrm{snapshot\_period}(t)}(t) > 0 \vee \mathrm{pos}(t) = 0 \wedge \left( \mathrm{u}^{z,0}_{\xi,j} = 0 \vee \mathrm{z}^{0}_{\xi,j} \text{ is defined} \right) \right) \wedge \mathrm{on}^{z}_{t,j}
+\overleftarrow{z}_{\xi,t,j} - z_{\xi,t,j} \le \widetilde{\mathrm{rd}}^{z,\mathrm{dn}}_{\xi,j} \cdot Z_{j} + \mathrm{M}^{z}_{\xi,j} - \mathrm{M}^{z}_{\xi,j} \cdot \mathit{dn}^{z}_{\xi,t,j} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{on}^{z,\mathrm{com,ext}}_{t,j} \wedge \left( \mathrm{rd}^{z}_{\xi,t,j} \text{ is defined} \vee \mathrm{rd}^{z,\mathrm{dn}}_{\xi,j} \text{ is defined} \right) \wedge \mathrm{prev}^{z}_{\xi,t,j}
 ```
 
 ### `Process-p_nom_modularity`
@@ -7886,12 +7873,12 @@ Process_com_ext_p_upper_cap:
     `Process-com-ext-p-upper-cap` — a committed extendable process runs
     at most what is available of the chosen build, whatever its status
   dims: [scenario, snapshot, process]
-  where: Process_committable AND Process_p_nom_extendable AND NOT (Process_p_nom_mod > 0) AND Process_active
+  where: Process_com_ext
   expression: Process_p <= Process_p_max_pu * (Process_p_nom_ext - Process_maintenance_pu * Process_maintenance_capacity)
 ```
 
 ```math
-z_{\xi,t,j} \le \overline{\mathrm{z}}_{\xi,t,j} \cdot \left( Z_{j} - \gamma^{z}_{\xi,j} \cdot \mu^{z,\mathrm{nom}}_{\xi,t,j} \right) \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{com}^{z}_{j} \wedge \mathrm{ext}^{z}_{j} \wedge \neg \left( \mathrm{z}^{\mathrm{mod}}_{j} > 0 \right) \wedge \mathrm{on}^{z}_{t,j}
+z_{\xi,t,j} \le \overline{\mathrm{z}}_{\xi,t,j} \cdot \left( Z_{j} - \gamma^{z}_{\xi,j} \cdot \mu^{z,\mathrm{nom}}_{\xi,t,j} \right) \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{on}^{z,\mathrm{com,ext}}_{t,j}
 ```
 
 ### `Process-com-ext-p-upper-bigM`
@@ -7902,12 +7889,12 @@ z_{\xi,t,j} \le \overline{\mathrm{z}}_{\xi,t,j} \cdot \left( Z_{j} - \gamma^{z}_
 Process_com_ext_p_upper_big_m:
   description: "`Process-com-ext-p-upper-bigM` — off, a process does not run; on, the big M is no bound"
   dims: [scenario, snapshot, process]
-  where: Process_committable AND Process_p_nom_extendable AND NOT (Process_p_nom_mod > 0) AND Process_active
+  where: Process_com_ext
   expression: Process_p <= Process_big_m * Process_status
 ```
 
 ```math
-z_{\xi,t,j} \le \mathrm{M}^{z}_{\xi,j} \cdot u^{z}_{\xi,t,j} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{com}^{z}_{j} \wedge \mathrm{ext}^{z}_{j} \wedge \neg \left( \mathrm{z}^{\mathrm{mod}}_{j} > 0 \right) \wedge \mathrm{on}^{z}_{t,j}
+z_{\xi,t,j} \le \mathrm{M}^{z}_{\xi,j} \cdot u^{z}_{\xi,t,j} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{on}^{z,\mathrm{com,ext}}_{t,j}
 ```
 
 ### `Process-com-ext-p-lower`
@@ -7920,7 +7907,7 @@ Process_com_ext_p_lower:
     `Process-com-ext-p-lower` — a committed extendable process runs at
     least its minimum of the chosen build; off, the big M releases the row
   dims: [scenario, snapshot, process]
-  where: Process_committable AND Process_p_nom_extendable AND NOT (Process_p_nom_mod > 0) AND Process_active
+  where: Process_com_ext
   expression: >-
     Process_p >=
     Process_p_min_pu * (Process_p_nom_ext - Process_maintenance_pu * Process_maintenance_capacity)
@@ -7928,7 +7915,7 @@ Process_com_ext_p_lower:
 ```
 
 ```math
-z_{\xi,t,j} \ge \underline{\mathrm{z}}_{\xi,t,j} \cdot \left( Z_{j} - \gamma^{z}_{\xi,j} \cdot \mu^{z,\mathrm{nom}}_{\xi,t,j} \right) + \mathrm{M}^{z}_{\xi,j} \cdot u^{z}_{\xi,t,j} - \mathrm{M}^{z}_{\xi,j} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{com}^{z}_{j} \wedge \mathrm{ext}^{z}_{j} \wedge \neg \left( \mathrm{z}^{\mathrm{mod}}_{j} > 0 \right) \wedge \mathrm{on}^{z}_{t,j}
+z_{\xi,t,j} \ge \underline{\mathrm{z}}_{\xi,t,j} \cdot \left( Z_{j} - \gamma^{z}_{\xi,j} \cdot \mu^{z,\mathrm{nom}}_{\xi,t,j} \right) + \mathrm{M}^{z}_{\xi,j} \cdot u^{z}_{\xi,t,j} - \mathrm{M}^{z}_{\xi,j} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{on}^{z,\mathrm{com,ext}}_{t,j}
 ```
 
 ### `Process-com-ext-p-lower-nonneg`
@@ -7942,14 +7929,12 @@ Process_com_ext_p_lower_nonneg:
     negative, internal power is also plainly non-negative, a row the big-M lower
     cannot assert while the process is off
   dims: [scenario, snapshot, process]
-  where: >-
-    Process_committable AND Process_p_nom_extendable
-    AND Process_p_min_pu_nonneg AND NOT (Process_p_nom_mod > 0) AND Process_active
+  where: Process_com_ext AND Process_p_min_pu_nonneg
   expression: Process_p >= 0
 ```
 
 ```math
-z_{\xi,t,j} \ge 0 \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{com}^{z}_{j} \wedge \mathrm{ext}^{z}_{j} \wedge \mathrm{nonneg}^{z}_{j} \wedge \neg \left( \mathrm{z}^{\mathrm{mod}}_{j} > 0 \right) \wedge \mathrm{on}^{z}_{t,j}
+z_{\xi,t,j} \ge 0 \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{on}^{z,\mathrm{com,ext}}_{t,j} \wedge \mathrm{nonneg}^{z}_{j}
 ```
 
 ### `Process-com-mod-p-lower`
@@ -7962,12 +7947,12 @@ Process_com_mod_p_lower:
     `Process-com-mod-p-lower` — a committed modular process runs at least
     its minimum of one module, whether the build is fixed or a decision
   dims: [scenario, snapshot, process]
-  where: Process_committable AND Process_p_nom_mod > 0 AND Process_active
+  where: Process_committed AND Process_p_nom_mod > 0
   expression: Process_p >= Process_p_min_pu * Process_p_nom_mod * (Process_status - Process_maintenance_pu * Process_maintenance_status)
 ```
 
 ```math
-z_{\xi,t,j} \ge \underline{\mathrm{z}}_{\xi,t,j} \cdot \mathrm{z}^{\mathrm{mod}}_{j} \cdot \left( u^{z}_{\xi,t,j} - \gamma^{z}_{\xi,j} \cdot \mu^{z,u}_{\xi,t,j} \right) \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{com}^{z}_{j} \wedge \mathrm{z}^{\mathrm{mod}}_{j} > 0 \wedge \mathrm{on}^{z}_{t,j}
+z_{\xi,t,j} \ge \underline{\mathrm{z}}_{\xi,t,j} \cdot \mathrm{z}^{\mathrm{mod}}_{j} \cdot \left( u^{z}_{\xi,t,j} - \gamma^{z}_{\xi,j} \cdot \mu^{z,u}_{\xi,t,j} \right) \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{on}^{z,\mathrm{com}}_{t,j} \wedge \mathrm{z}^{\mathrm{mod}}_{j} > 0
 ```
 
 ### `Process-com-mod-p-upper`
@@ -7980,12 +7965,12 @@ Process_com_mod_p_upper:
     `Process-com-mod-p-upper` — a committed modular process runs at most
     one module's share, whether the build is fixed or a decision
   dims: [scenario, snapshot, process]
-  where: Process_committable AND Process_p_nom_mod > 0 AND Process_active
+  where: Process_committed AND Process_p_nom_mod > 0
   expression: Process_p <= Process_p_max_pu * Process_p_nom_mod * (Process_status - Process_maintenance_pu * Process_maintenance_status)
 ```
 
 ```math
-z_{\xi,t,j} \le \overline{\mathrm{z}}_{\xi,t,j} \cdot \mathrm{z}^{\mathrm{mod}}_{j} \cdot \left( u^{z}_{\xi,t,j} - \gamma^{z}_{\xi,j} \cdot \mu^{z,u}_{\xi,t,j} \right) \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{com}^{z}_{j} \wedge \mathrm{z}^{\mathrm{mod}}_{j} > 0 \wedge \mathrm{on}^{z}_{t,j}
+z_{\xi,t,j} \le \overline{\mathrm{z}}_{\xi,t,j} \cdot \mathrm{z}^{\mathrm{mod}}_{j} \cdot \left( u^{z}_{\xi,t,j} - \gamma^{z}_{\xi,j} \cdot \mu^{z,u}_{\xi,t,j} \right) \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{on}^{z,\mathrm{com}}_{t,j} \wedge \mathrm{z}^{\mathrm{mod}}_{j} > 0
 ```
 
 ### `Process-status-p-fixed-upper`
@@ -7999,12 +7984,12 @@ Process_status_p_fixed_upper:
     place, an explicit row as PyPSA writes it: one where the build is not
     modular, and the fixed build's whole count of modules where it is
   dims: [scenario, snapshot, process]
-  where: Process_committable AND NOT (Process_p_nom_extendable AND Process_p_nom_mod > 0) AND Process_active
+  where: Process_committed AND NOT (Process_p_nom_extendable AND Process_p_nom_mod > 0)
   expression: Process_status <= Process_modules_installed
 ```
 
 ```math
-u^{z}_{\xi,t,j} \le \mathrm{N}^{z,\mathrm{fix}}_{\xi,j} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{com}^{z}_{j} \wedge \neg \left( \mathrm{ext}^{z}_{j} \wedge \mathrm{z}^{\mathrm{mod}}_{j} > 0 \right) \wedge \mathrm{on}^{z}_{t,j}
+u^{z}_{\xi,t,j} \le \mathrm{N}^{z,\mathrm{fix}}_{\xi,j} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{on}^{z,\mathrm{com}}_{t,j} \wedge \neg \left( \mathrm{ext}^{z}_{j} \wedge \mathrm{z}^{\mathrm{mod}}_{j} > 0 \right)
 ```
 
 ### `Process-start_up-p-fixed-upper`
@@ -8018,12 +8003,12 @@ Process_start_up_p_fixed_upper:
     place, an explicit row as PyPSA writes it: one where the build is not
     modular, and the fixed build's whole count of modules where it is
   dims: [scenario, snapshot, process]
-  where: Process_committable AND NOT (Process_p_nom_extendable AND Process_p_nom_mod > 0) AND Process_active
+  where: Process_committed AND NOT (Process_p_nom_extendable AND Process_p_nom_mod > 0)
   expression: Process_start_up <= Process_modules_installed
 ```
 
 ```math
-\mathit{up}^{z}_{\xi,t,j} \le \mathrm{N}^{z,\mathrm{fix}}_{\xi,j} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{com}^{z}_{j} \wedge \neg \left( \mathrm{ext}^{z}_{j} \wedge \mathrm{z}^{\mathrm{mod}}_{j} > 0 \right) \wedge \mathrm{on}^{z}_{t,j}
+\mathit{up}^{z}_{\xi,t,j} \le \mathrm{N}^{z,\mathrm{fix}}_{\xi,j} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{on}^{z,\mathrm{com}}_{t,j} \wedge \neg \left( \mathrm{ext}^{z}_{j} \wedge \mathrm{z}^{\mathrm{mod}}_{j} > 0 \right)
 ```
 
 ### `Process-shut_down-p-fixed-upper`
@@ -8037,12 +8022,12 @@ Process_shut_down_p_fixed_upper:
     place, an explicit row as PyPSA writes it: one where the build is not
     modular, and the fixed build's whole count of modules where it is
   dims: [scenario, snapshot, process]
-  where: Process_committable AND NOT (Process_p_nom_extendable AND Process_p_nom_mod > 0) AND Process_active
+  where: Process_committed AND NOT (Process_p_nom_extendable AND Process_p_nom_mod > 0)
   expression: Process_shut_down <= Process_modules_installed
 ```
 
 ```math
-\mathit{dn}^{z}_{\xi,t,j} \le \mathrm{N}^{z,\mathrm{fix}}_{\xi,j} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{com}^{z}_{j} \wedge \neg \left( \mathrm{ext}^{z}_{j} \wedge \mathrm{z}^{\mathrm{mod}}_{j} > 0 \right) \wedge \mathrm{on}^{z}_{t,j}
+\mathit{dn}^{z}_{\xi,t,j} \le \mathrm{N}^{z,\mathrm{fix}}_{\xi,j} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{on}^{z,\mathrm{com}}_{t,j} \wedge \neg \left( \mathrm{ext}^{z}_{j} \wedge \mathrm{z}^{\mathrm{mod}}_{j} > 0 \right)
 ```
 
 ### `Process-status-p_nom-variable-upper`
@@ -8053,12 +8038,12 @@ Process_shut_down_p_fixed_upper:
 Process_status_p_nom_variable_upper:
   description: "`Process-status-p_nom-variable-upper` — a modular process is on only where a module is built"
   dims: [scenario, snapshot, process]
-  where: Process_committable AND Process_p_nom_extendable AND Process_p_nom_mod > 0 AND Process_active
+  where: Process_committed AND Process_p_nom_extendable AND Process_p_nom_mod > 0
   expression: Process_status <= Process_n_mod
 ```
 
 ```math
-u^{z}_{\xi,t,j} \le N^{z}_{j} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{com}^{z}_{j} \wedge \mathrm{ext}^{z}_{j} \wedge \mathrm{z}^{\mathrm{mod}}_{j} > 0 \wedge \mathrm{on}^{z}_{t,j}
+u^{z}_{\xi,t,j} \le N^{z}_{j} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{on}^{z,\mathrm{com}}_{t,j} \wedge \mathrm{ext}^{z}_{j} \wedge \mathrm{z}^{\mathrm{mod}}_{j} > 0
 ```
 
 ### `Process-start_up-p_nom-variable-upper`
@@ -8069,12 +8054,12 @@ u^{z}_{\xi,t,j} \le N^{z}_{j} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\
 Process_start_up_p_nom_variable_upper:
   description: "`Process-start_up-p_nom-variable-upper` — a modular process starts only where a module is built"
   dims: [scenario, snapshot, process]
-  where: Process_committable AND Process_p_nom_extendable AND Process_p_nom_mod > 0 AND Process_active
+  where: Process_committed AND Process_p_nom_extendable AND Process_p_nom_mod > 0
   expression: Process_start_up <= Process_n_mod
 ```
 
 ```math
-\mathit{up}^{z}_{\xi,t,j} \le N^{z}_{j} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{com}^{z}_{j} \wedge \mathrm{ext}^{z}_{j} \wedge \mathrm{z}^{\mathrm{mod}}_{j} > 0 \wedge \mathrm{on}^{z}_{t,j}
+\mathit{up}^{z}_{\xi,t,j} \le N^{z}_{j} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{on}^{z,\mathrm{com}}_{t,j} \wedge \mathrm{ext}^{z}_{j} \wedge \mathrm{z}^{\mathrm{mod}}_{j} > 0
 ```
 
 ### `Process-shut_down-p_nom-variable-upper`
@@ -8085,12 +8070,12 @@ Process_start_up_p_nom_variable_upper:
 Process_shut_down_p_nom_variable_upper:
   description: "`Process-shut_down-p_nom-variable-upper` — a modular process stops only where a module is built"
   dims: [scenario, snapshot, process]
-  where: Process_committable AND Process_p_nom_extendable AND Process_p_nom_mod > 0 AND Process_active
+  where: Process_committed AND Process_p_nom_extendable AND Process_p_nom_mod > 0
   expression: Process_shut_down <= Process_n_mod
 ```
 
 ```math
-\mathit{dn}^{z}_{\xi,t,j} \le N^{z}_{j} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{com}^{z}_{j} \wedge \mathrm{ext}^{z}_{j} \wedge \mathrm{z}^{\mathrm{mod}}_{j} > 0 \wedge \mathrm{on}^{z}_{t,j}
+\mathit{dn}^{z}_{\xi,t,j} \le N^{z}_{j} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{on}^{z,\mathrm{com}}_{t,j} \wedge \mathrm{ext}^{z}_{j} \wedge \mathrm{z}^{\mathrm{mod}}_{j} > 0
 ```
 
 ### `Process-maint-event-count`
@@ -8154,12 +8139,12 @@ Process_maintcap_upper:
     `Process-maintcap_upper` — the build taken off is at most the chosen build in
     maintenance, and at most the build less its floor out of it
   dims: [scenario, snapshot, process]
-  where: Process_maintainable AND Process_p_nom_extendable AND NOT (Process_committable AND Process_p_nom_mod > 0) AND Process_active
+  where: Process_maint_ext
   expression: Process_maintenance_capacity <= Process_p_nom_ext - Process_p_nom_min * (1 - Process_maintenance)
 ```
 
 ```math
-\mu^{z,\mathrm{nom}}_{\xi,t,j} \le Z_{j} - \underline{\mathrm{z}}^{\mathrm{nom}}_{\xi,j} \cdot \left( 1 - \mu^{z}_{\xi,t,j} \right) \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{mnt}^{z}_{j} \wedge \mathrm{ext}^{z}_{j} \wedge \neg \left( \mathrm{com}^{z}_{j} \wedge \mathrm{z}^{\mathrm{mod}}_{j} > 0 \right) \wedge \mathrm{on}^{z}_{t,j}
+\mu^{z,\mathrm{nom}}_{\xi,t,j} \le Z_{j} - \underline{\mathrm{z}}^{\mathrm{nom}}_{\xi,j} \cdot \left( 1 - \mu^{z}_{\xi,t,j} \right) \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{on}^{z,\mathrm{mnt,ext}}_{t,j}
 ```
 
 ### `Process-maintcap_upper_nommax`
@@ -8170,12 +8155,12 @@ Process_maintcap_upper:
 Process_maintcap_upper_nommax:
   description: "`Process-maintcap_upper_nommax` — out of maintenance, no build is taken off"
   dims: [scenario, snapshot, process]
-  where: Process_maintainable AND Process_p_nom_extendable AND NOT (Process_committable AND Process_p_nom_mod > 0) AND Process_active
+  where: Process_maint_ext
   expression: Process_maintenance_capacity <= Process_p_nom_max * Process_maintenance
 ```
 
 ```math
-\mu^{z,\mathrm{nom}}_{\xi,t,j} \le \overline{\mathrm{z}}^{\mathrm{nom}}_{\xi,j} \cdot \mu^{z}_{\xi,t,j} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{mnt}^{z}_{j} \wedge \mathrm{ext}^{z}_{j} \wedge \neg \left( \mathrm{com}^{z}_{j} \wedge \mathrm{z}^{\mathrm{mod}}_{j} > 0 \right) \wedge \mathrm{on}^{z}_{t,j}
+\mu^{z,\mathrm{nom}}_{\xi,t,j} \le \overline{\mathrm{z}}^{\mathrm{nom}}_{\xi,j} \cdot \mu^{z}_{\xi,t,j} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{on}^{z,\mathrm{mnt,ext}}_{t,j}
 ```
 
 ### `Process-maintcap_lower_nommax`
@@ -8186,12 +8171,12 @@ Process_maintcap_upper_nommax:
 Process_maintcap_lower_nommax:
   description: "`Process-maintcap_lower_nommax` — in maintenance, the whole chosen build is taken off"
   dims: [scenario, snapshot, process]
-  where: Process_maintainable AND Process_p_nom_extendable AND NOT (Process_committable AND Process_p_nom_mod > 0) AND Process_active
+  where: Process_maint_ext
   expression: Process_maintenance_capacity >= Process_p_nom_ext - Process_p_nom_max * (1 - Process_maintenance)
 ```
 
 ```math
-\mu^{z,\mathrm{nom}}_{\xi,t,j} \ge Z_{j} - \overline{\mathrm{z}}^{\mathrm{nom}}_{\xi,j} \cdot \left( 1 - \mu^{z}_{\xi,t,j} \right) \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{mnt}^{z}_{j} \wedge \mathrm{ext}^{z}_{j} \wedge \neg \left( \mathrm{com}^{z}_{j} \wedge \mathrm{z}^{\mathrm{mod}}_{j} > 0 \right) \wedge \mathrm{on}^{z}_{t,j}
+\mu^{z,\mathrm{nom}}_{\xi,t,j} \ge Z_{j} - \overline{\mathrm{z}}^{\mathrm{nom}}_{\xi,j} \cdot \left( 1 - \mu^{z}_{\xi,t,j} \right) \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{on}^{z,\mathrm{mnt,ext}}_{t,j}
 ```
 
 ### `Process-maintcap_lower_nommin`
@@ -8202,12 +8187,12 @@ Process_maintcap_lower_nommax:
 Process_maintcap_lower_nommin:
   description: "`Process-maintcap_lower_nommin` — in maintenance, at least the floor of the build is taken off"
   dims: [scenario, snapshot, process]
-  where: Process_maintainable AND Process_p_nom_extendable AND NOT (Process_committable AND Process_p_nom_mod > 0) AND Process_active AND Process_p_nom_min > 0
+  where: Process_maint_ext AND Process_p_nom_min > 0
   expression: Process_maintenance_capacity >= Process_p_nom_min * Process_maintenance
 ```
 
 ```math
-\mu^{z,\mathrm{nom}}_{\xi,t,j} \ge \underline{\mathrm{z}}^{\mathrm{nom}}_{\xi,j} \cdot \mu^{z}_{\xi,t,j} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{mnt}^{z}_{j} \wedge \mathrm{ext}^{z}_{j} \wedge \neg \left( \mathrm{com}^{z}_{j} \wedge \mathrm{z}^{\mathrm{mod}}_{j} > 0 \right) \wedge \mathrm{on}^{z}_{t,j} \wedge \underline{\mathrm{z}}^{\mathrm{nom}}_{\xi,j} > 0
+\mu^{z,\mathrm{nom}}_{\xi,t,j} \ge \underline{\mathrm{z}}^{\mathrm{nom}}_{\xi,j} \cdot \mu^{z}_{\xi,t,j} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{on}^{z,\mathrm{mnt,ext}}_{t,j} \wedge \underline{\mathrm{z}}^{\mathrm{nom}}_{\xi,j} > 0
 ```
 
 ### `Process-maint-status-le-status`
@@ -8218,12 +8203,12 @@ Process_maintcap_lower_nommin:
 Process_maint_status_le_status:
   description: "`Process-maint-status-le-status` — the status in maintenance is at most the status"
   dims: [scenario, snapshot, process]
-  where: Process_maintainable AND Process_committable AND NOT Process_p_nom_extendable AND NOT (Process_p_nom_mod > 0) AND Process_active
+  where: Process_maintainable AND Process_committed AND NOT Process_p_nom_extendable AND NOT (Process_p_nom_mod > 0)
   expression: Process_maintenance_status <= Process_status
 ```
 
 ```math
-\mu^{z,u}_{\xi,t,j} \le u^{z}_{\xi,t,j} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{mnt}^{z}_{j} \wedge \mathrm{com}^{z}_{j} \wedge \neg \mathrm{ext}^{z}_{j} \wedge \neg \left( \mathrm{z}^{\mathrm{mod}}_{j} > 0 \right) \wedge \mathrm{on}^{z}_{t,j}
+\mu^{z,u}_{\xi,t,j} \le u^{z}_{\xi,t,j} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{mnt}^{z}_{j} \wedge \mathrm{on}^{z,\mathrm{com}}_{t,j} \wedge \neg \mathrm{ext}^{z}_{j} \wedge \neg \left( \mathrm{z}^{\mathrm{mod}}_{j} > 0 \right)
 ```
 
 ### `Process-maint-status-le-maint`
@@ -8234,12 +8219,12 @@ Process_maint_status_le_status:
 Process_maint_status_le_maint:
   description: "`Process-maint-status-le-maint` — out of maintenance, the status in maintenance is zero"
   dims: [scenario, snapshot, process]
-  where: Process_maintainable AND Process_committable AND NOT Process_p_nom_extendable AND NOT (Process_p_nom_mod > 0) AND Process_active
+  where: Process_maintainable AND Process_committed AND NOT Process_p_nom_extendable AND NOT (Process_p_nom_mod > 0)
   expression: Process_maintenance_status <= Process_maintenance
 ```
 
 ```math
-\mu^{z,u}_{\xi,t,j} \le \mu^{z}_{\xi,t,j} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{mnt}^{z}_{j} \wedge \mathrm{com}^{z}_{j} \wedge \neg \mathrm{ext}^{z}_{j} \wedge \neg \left( \mathrm{z}^{\mathrm{mod}}_{j} > 0 \right) \wedge \mathrm{on}^{z}_{t,j}
+\mu^{z,u}_{\xi,t,j} \le \mu^{z}_{\xi,t,j} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{mnt}^{z}_{j} \wedge \mathrm{on}^{z,\mathrm{com}}_{t,j} \wedge \neg \mathrm{ext}^{z}_{j} \wedge \neg \left( \mathrm{z}^{\mathrm{mod}}_{j} > 0 \right)
 ```
 
 ### `Process-maint-status-lb`
@@ -8250,12 +8235,12 @@ Process_maint_status_le_maint:
 Process_maint_status_lb:
   description: "`Process-maint-status-lb` — on and in maintenance, the status in maintenance is one"
   dims: [scenario, snapshot, process]
-  where: Process_maintainable AND Process_committable AND NOT Process_p_nom_extendable AND NOT (Process_p_nom_mod > 0) AND Process_active
+  where: Process_maintainable AND Process_committed AND NOT Process_p_nom_extendable AND NOT (Process_p_nom_mod > 0)
   expression: Process_maintenance_status >= Process_status + Process_maintenance - 1
 ```
 
 ```math
-\mu^{z,u}_{\xi,t,j} \ge u^{z}_{\xi,t,j} + \mu^{z}_{\xi,t,j} - 1 \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{mnt}^{z}_{j} \wedge \mathrm{com}^{z}_{j} \wedge \neg \mathrm{ext}^{z}_{j} \wedge \neg \left( \mathrm{z}^{\mathrm{mod}}_{j} > 0 \right) \wedge \mathrm{on}^{z}_{t,j}
+\mu^{z,u}_{\xi,t,j} \ge u^{z}_{\xi,t,j} + \mu^{z}_{\xi,t,j} - 1 \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{mnt}^{z}_{j} \wedge \mathrm{on}^{z,\mathrm{com}}_{t,j} \wedge \neg \mathrm{ext}^{z}_{j} \wedge \neg \left( \mathrm{z}^{\mathrm{mod}}_{j} > 0 \right)
 ```
 
 ### `Process-maint-modstatus-le-status`
@@ -8266,12 +8251,12 @@ Process_maint_status_lb:
 Process_maint_modstatus_le_status:
   description: "`Process-maint-modstatus-le-status` — the modules on in maintenance are at most the modules on"
   dims: [scenario, snapshot, process]
-  where: Process_maintainable AND Process_committable AND Process_p_nom_mod > 0 AND Process_active
+  where: Process_maintainable AND Process_committed AND Process_p_nom_mod > 0
   expression: Process_maintenance_status <= Process_status
 ```
 
 ```math
-\mu^{z,u}_{\xi,t,j} \le u^{z}_{\xi,t,j} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{mnt}^{z}_{j} \wedge \mathrm{com}^{z}_{j} \wedge \mathrm{z}^{\mathrm{mod}}_{j} > 0 \wedge \mathrm{on}^{z}_{t,j}
+\mu^{z,u}_{\xi,t,j} \le u^{z}_{\xi,t,j} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{mnt}^{z}_{j} \wedge \mathrm{on}^{z,\mathrm{com}}_{t,j} \wedge \mathrm{z}^{\mathrm{mod}}_{j} > 0
 ```
 
 ### `Process-maint-modstatus-le-maint`
@@ -8284,12 +8269,12 @@ Process_maint_modstatus_le_maint:
     `Process-maint-modstatus-le-maint` — out of maintenance, no module is on in
     maintenance; in it, at most the modules the build cap holds
   dims: [scenario, snapshot, process]
-  where: Process_maintainable AND Process_committable AND Process_p_nom_mod > 0 AND Process_active
+  where: Process_maintainable AND Process_committed AND Process_p_nom_mod > 0
   expression: Process_maintenance_status <= Process_p_nom_max / Process_p_nom_mod * Process_maintenance
 ```
 
 ```math
-\mu^{z,u}_{\xi,t,j} \le \frac{\overline{\mathrm{z}}^{\mathrm{nom}}_{\xi,j}}{\mathrm{z}^{\mathrm{mod}}_{j}} \cdot \mu^{z}_{\xi,t,j} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{mnt}^{z}_{j} \wedge \mathrm{com}^{z}_{j} \wedge \mathrm{z}^{\mathrm{mod}}_{j} > 0 \wedge \mathrm{on}^{z}_{t,j}
+\mu^{z,u}_{\xi,t,j} \le \frac{\overline{\mathrm{z}}^{\mathrm{nom}}_{\xi,j}}{\mathrm{z}^{\mathrm{mod}}_{j}} \cdot \mu^{z}_{\xi,t,j} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{mnt}^{z}_{j} \wedge \mathrm{on}^{z,\mathrm{com}}_{t,j} \wedge \mathrm{z}^{\mathrm{mod}}_{j} > 0
 ```
 
 ### `Process-maint-modstatus-lb`
@@ -8300,12 +8285,12 @@ Process_maint_modstatus_le_maint:
 Process_maint_modstatus_lb:
   description: "`Process-maint-modstatus-lb` — in maintenance, every module on is on in maintenance"
   dims: [scenario, snapshot, process]
-  where: Process_maintainable AND Process_committable AND Process_p_nom_mod > 0 AND Process_active
+  where: Process_maintainable AND Process_committed AND Process_p_nom_mod > 0
   expression: Process_maintenance_status >= Process_status - Process_p_nom_max / Process_p_nom_mod * (1 - Process_maintenance)
 ```
 
 ```math
-\mu^{z,u}_{\xi,t,j} \ge u^{z}_{\xi,t,j} - \frac{\overline{\mathrm{z}}^{\mathrm{nom}}_{\xi,j}}{\mathrm{z}^{\mathrm{mod}}_{j}} \cdot \left( 1 - \mu^{z}_{\xi,t,j} \right) \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{mnt}^{z}_{j} \wedge \mathrm{com}^{z}_{j} \wedge \mathrm{z}^{\mathrm{mod}}_{j} > 0 \wedge \mathrm{on}^{z}_{t,j}
+\mu^{z,u}_{\xi,t,j} \ge u^{z}_{\xi,t,j} - \frac{\overline{\mathrm{z}}^{\mathrm{nom}}_{\xi,j}}{\mathrm{z}^{\mathrm{mod}}_{j}} \cdot \left( 1 - \mu^{z}_{\xi,t,j} \right) \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{mnt}^{z}_{j} \wedge \mathrm{on}^{z,\mathrm{com}}_{t,j} \wedge \mathrm{z}^{\mathrm{mod}}_{j} > 0
 ```
 
 ### `Line-fix-s-lower`
@@ -8497,12 +8482,12 @@ s_{\xi,t,k} \le \frac{\overline{\delta}_{\xi,k} \cdot \frac{3.141592653589793}{1
 Line_loss_upper:
   description: "`Line-loss_upper` — a line dissipates at most the loss at its rating"
   dims: [scenario, snapshot, line]
-  where: transmission_losses AND Line_active
+  where: Line_lossy
   expression: Line_loss <= Line_loss_max
 ```
 
 ```math
-\ell_{\xi,t,k} \le \overline{\ell}_{\xi,t,k} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ k \in \mathcal{K} \,:\, \mathrm{lossy} \wedge \mathrm{on}^{s}_{t,k}
+\ell_{\xi,t,k} \le \overline{\ell}_{\xi,t,k} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ k \in \mathcal{K} \,:\, \mathrm{on}^{s,\mathrm{lossy}}_{t,k}
 ```
 
 ### `Line-loss_tangents-{k}-1`
@@ -8517,12 +8502,12 @@ Line_loss_tangents_forward:
     `k`, or one row stacked over its `secant` axis, and this block states them
     all over the segment dimension
   dims: [scenario, snapshot, line, segment]
-  where: transmission_losses AND Line_active
+  where: Line_lossy
   expression: Line_loss + Line_loss_slope * Line_s >= Line_loss_offset
 ```
 
 ```math
-\ell_{\xi,t,k} + \mathrm{a}_{\xi,t,k,b} \cdot s_{\xi,t,k} \ge \mathrm{b}_{\xi,t,k,b} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ k \in \mathcal{K},\ b \in \mathcal{B} \,:\, \mathrm{lossy} \wedge \mathrm{on}^{s}_{t,k}
+\ell_{\xi,t,k} + \mathrm{a}_{\xi,t,k,b} \cdot s_{\xi,t,k} \ge \mathrm{b}_{\xi,t,k,b} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ k \in \mathcal{K},\ b \in \mathcal{B} \,:\, \mathrm{on}^{s,\mathrm{lossy}}_{t,k}
 ```
 
 ### `Line-loss_tangents-{k}--1`
@@ -8535,12 +8520,12 @@ Line_loss_tangents_reverse:
     `Line-loss_tangents-{k}--1`, `Line-loss_secants-neg` — the same fan
     mirrored, the loss depending on the flow's magnitude
   dims: [scenario, snapshot, line, segment]
-  where: transmission_losses AND Line_active
+  where: Line_lossy
   expression: Line_loss - Line_loss_slope * Line_s >= Line_loss_offset
 ```
 
 ```math
-\ell_{\xi,t,k} - \mathrm{a}_{\xi,t,k,b} \cdot s_{\xi,t,k} \ge \mathrm{b}_{\xi,t,k,b} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ k \in \mathcal{K},\ b \in \mathcal{B} \,:\, \mathrm{lossy} \wedge \mathrm{on}^{s}_{t,k}
+\ell_{\xi,t,k} - \mathrm{a}_{\xi,t,k,b} \cdot s_{\xi,t,k} \ge \mathrm{b}_{\xi,t,k,b} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ k \in \mathcal{K},\ b \in \mathcal{B} \,:\, \mathrm{on}^{s,\mathrm{lossy}}_{t,k}
 ```
 
 ### `Transformer-fix-s-lower`
@@ -8771,12 +8756,12 @@ Transformer_v_ang_var_upper:
 Transformer_loss_upper:
   description: "`Transformer-loss_upper` — a transformer dissipates at most the loss at its rating"
   dims: [scenario, snapshot, transformer]
-  where: transmission_losses AND Transformer_active
+  where: Transformer_lossy
   expression: Transformer_loss <= Transformer_loss_max
 ```
 
 ```math
-\ell^{\sigma}_{\xi,t,m} \le \overline{\ell}^{\sigma}_{\xi,t,m} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ m \in \mathcal{M} \,:\, \mathrm{lossy} \wedge \mathrm{on}^{\sigma}_{t,m}
+\ell^{\sigma}_{\xi,t,m} \le \overline{\ell}^{\sigma}_{\xi,t,m} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ m \in \mathcal{M} \,:\, \mathrm{on}^{\sigma,\mathrm{lossy}}_{t,m}
 ```
 
 ### `Transformer-loss_tangents-{k}-1`
@@ -8790,12 +8775,12 @@ Transformer_loss_tangents_forward:
     loss sits above every cut to its curve for flow one way, as a line's
     does, over the segment dimension
   dims: [scenario, snapshot, transformer, segment]
-  where: transmission_losses AND Transformer_active
+  where: Transformer_lossy
   expression: Transformer_loss + Transformer_loss_slope * Transformer_s >= Transformer_loss_offset
 ```
 
 ```math
-\ell^{\sigma}_{\xi,t,m} + \mathrm{a}^{\sigma}_{\xi,t,m,b} \cdot \sigma_{\xi,t,m} \ge \mathrm{b}^{\sigma}_{\xi,t,m,b} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ m \in \mathcal{M},\ b \in \mathcal{B} \,:\, \mathrm{lossy} \wedge \mathrm{on}^{\sigma}_{t,m}
+\ell^{\sigma}_{\xi,t,m} + \mathrm{a}^{\sigma}_{\xi,t,m,b} \cdot \sigma_{\xi,t,m} \ge \mathrm{b}^{\sigma}_{\xi,t,m,b} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ m \in \mathcal{M},\ b \in \mathcal{B} \,:\, \mathrm{on}^{\sigma,\mathrm{lossy}}_{t,m}
 ```
 
 ### `Transformer-loss_tangents-{k}--1`
@@ -8808,12 +8793,12 @@ Transformer_loss_tangents_reverse:
     `Transformer-loss_tangents-{k}--1`, `Transformer-loss_secants-neg` — the
     same fan mirrored, the loss depending on the flow's magnitude
   dims: [scenario, snapshot, transformer, segment]
-  where: transmission_losses AND Transformer_active
+  where: Transformer_lossy
   expression: Transformer_loss - Transformer_loss_slope * Transformer_s >= Transformer_loss_offset
 ```
 
 ```math
-\ell^{\sigma}_{\xi,t,m} - \mathrm{a}^{\sigma}_{\xi,t,m,b} \cdot \sigma_{\xi,t,m} \ge \mathrm{b}^{\sigma}_{\xi,t,m,b} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ m \in \mathcal{M},\ b \in \mathcal{B} \,:\, \mathrm{lossy} \wedge \mathrm{on}^{\sigma}_{t,m}
+\ell^{\sigma}_{\xi,t,m} - \mathrm{a}^{\sigma}_{\xi,t,m,b} \cdot \sigma_{\xi,t,m} \ge \mathrm{b}^{\sigma}_{\xi,t,m,b} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ m \in \mathcal{M},\ b \in \mathcal{B} \,:\, \mathrm{on}^{\sigma,\mathrm{lossy}}_{t,m}
 ```
 
 ### `Line-fix-s-lower-security-for-{c}-outage-in-sub-network-{n}`
@@ -9039,13 +9024,13 @@ Generator_p_ramp_limit_up:
   where: >-
     (Generator_ramp_limit_up OR Generator_ramp_limit_start_up)
     AND NOT (Generator_committable AND Generator_p_nom_extendable AND NOT (Generator_p_nom_mod > 0))
-    AND (position(snapshot, within=snapshot_period[period]) > 0 OR (position(snapshot) == 0 AND (Generator_status_initial == 0 OR Generator_p_init)))
+    AND Generator_ramps_from_previous
     AND Generator_active
   expression: Generator_p - Generator_previous_p <= Generator_ramp_up_allowance
 ```
 
 ```math
-p_{\xi,t,g} - \overleftarrow{p}_{\xi,t,g} \le \Delta^{+}_{\xi,t,g} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \left( \mathrm{ru}_{\xi,t,g} \text{ is defined} \vee \mathrm{ru}^{\mathrm{up}}_{\xi,g} \text{ is defined} \right) \wedge \neg \left( \mathrm{com}_{g} \wedge \mathrm{ext}_{g} \wedge \neg \left( \mathrm{p}^{\mathrm{mod}}_{g} > 0 \right) \right) \wedge \left( \mathrm{pos}_{\mathrm{snapshot\_period}(t)}(t) > 0 \vee \mathrm{pos}(t) = 0 \wedge \left( \mathrm{u}^{0}_{\xi,g} = 0 \vee \mathrm{p}^{0}_{\xi,g} \text{ is defined} \right) \right) \wedge \mathrm{on}_{t,g}
+p_{\xi,t,g} - \overleftarrow{p}_{\xi,t,g} \le \Delta^{+}_{\xi,t,g} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \left( \mathrm{ru}_{\xi,t,g} \text{ is defined} \vee \mathrm{ru}^{\mathrm{up}}_{\xi,g} \text{ is defined} \right) \wedge \neg \left( \mathrm{com}_{g} \wedge \mathrm{ext}_{g} \wedge \neg \left( \mathrm{p}^{\mathrm{mod}}_{g} > 0 \right) \right) \wedge \mathrm{prev}_{\xi,t,g} \wedge \mathrm{on}_{t,g}
 ```
 
 ### `Generator-p-ramp_limit_down`
@@ -9065,13 +9050,13 @@ Generator_p_ramp_limit_down:
   where: >-
     (Generator_ramp_limit_down OR Generator_ramp_limit_shut_down)
     AND NOT (Generator_committable AND Generator_p_nom_extendable AND NOT (Generator_p_nom_mod > 0))
-    AND (position(snapshot, within=snapshot_period[period]) > 0 OR (position(snapshot) == 0 AND (Generator_status_initial == 0 OR Generator_p_init)))
+    AND Generator_ramps_from_previous
     AND Generator_active
   expression: Generator_previous_p - Generator_p <= Generator_ramp_down_allowance
 ```
 
 ```math
-\overleftarrow{p}_{\xi,t,g} - p_{\xi,t,g} \le \Delta^{-}_{\xi,t,g} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \left( \mathrm{rd}_{\xi,t,g} \text{ is defined} \vee \mathrm{rd}^{\mathrm{dn}}_{\xi,g} \text{ is defined} \right) \wedge \neg \left( \mathrm{com}_{g} \wedge \mathrm{ext}_{g} \wedge \neg \left( \mathrm{p}^{\mathrm{mod}}_{g} > 0 \right) \right) \wedge \left( \mathrm{pos}_{\mathrm{snapshot\_period}(t)}(t) > 0 \vee \mathrm{pos}(t) = 0 \wedge \left( \mathrm{u}^{0}_{\xi,g} = 0 \vee \mathrm{p}^{0}_{\xi,g} \text{ is defined} \right) \right) \wedge \mathrm{on}_{t,g}
+\overleftarrow{p}_{\xi,t,g} - p_{\xi,t,g} \le \Delta^{-}_{\xi,t,g} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \left( \mathrm{rd}_{\xi,t,g} \text{ is defined} \vee \mathrm{rd}^{\mathrm{dn}}_{\xi,g} \text{ is defined} \right) \wedge \neg \left( \mathrm{com}_{g} \wedge \mathrm{ext}_{g} \wedge \neg \left( \mathrm{p}^{\mathrm{mod}}_{g} > 0 \right) \right) \wedge \mathrm{prev}_{\xi,t,g} \wedge \mathrm{on}_{t,g}
 ```
 
 ### `Link-p-ramp_limit_up`
@@ -9091,13 +9076,13 @@ Link_p_ramp_limit_up:
   where: >-
     (Link_ramp_limit_up OR Link_ramp_limit_start_up)
     AND NOT (Link_committable AND Link_p_nom_extendable AND NOT (Link_p_nom_mod > 0))
-    AND (position(snapshot, within=snapshot_period[period]) > 0 OR (position(snapshot) == 0 AND (Link_status_initial == 0 OR Link_p_init)))
+    AND Link_ramps_from_previous
     AND Link_active
   expression: Link_p - Link_previous_p <= Link_ramp_up_allowance
 ```
 
 ```math
-f_{\xi,t,l} - \overleftarrow{f}_{\xi,t,l} \le \Delta^{f,+}_{\xi,t,l} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \left( \mathrm{ru}^{f}_{\xi,t,l} \text{ is defined} \vee \mathrm{ru}^{f,\mathrm{up}}_{\xi,l} \text{ is defined} \right) \wedge \neg \left( \mathrm{com}^{f}_{l} \wedge \mathrm{ext}^{f}_{l} \wedge \neg \left( \mathrm{f}^{\mathrm{mod}}_{l} > 0 \right) \right) \wedge \left( \mathrm{pos}_{\mathrm{snapshot\_period}(t)}(t) > 0 \vee \mathrm{pos}(t) = 0 \wedge \left( \mathrm{u}^{f,0}_{\xi,l} = 0 \vee \mathrm{f}^{0}_{\xi,l} \text{ is defined} \right) \right) \wedge \mathrm{on}^{f}_{t,l}
+f_{\xi,t,l} - \overleftarrow{f}_{\xi,t,l} \le \Delta^{f,+}_{\xi,t,l} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \left( \mathrm{ru}^{f}_{\xi,t,l} \text{ is defined} \vee \mathrm{ru}^{f,\mathrm{up}}_{\xi,l} \text{ is defined} \right) \wedge \neg \left( \mathrm{com}^{f}_{l} \wedge \mathrm{ext}^{f}_{l} \wedge \neg \left( \mathrm{f}^{\mathrm{mod}}_{l} > 0 \right) \right) \wedge \mathrm{prev}^{f}_{\xi,t,l} \wedge \mathrm{on}^{f}_{t,l}
 ```
 
 ### `Link-p-ramp_limit_down`
@@ -9117,13 +9102,13 @@ Link_p_ramp_limit_down:
   where: >-
     (Link_ramp_limit_down OR Link_ramp_limit_shut_down)
     AND NOT (Link_committable AND Link_p_nom_extendable AND NOT (Link_p_nom_mod > 0))
-    AND (position(snapshot, within=snapshot_period[period]) > 0 OR (position(snapshot) == 0 AND (Link_status_initial == 0 OR Link_p_init)))
+    AND Link_ramps_from_previous
     AND Link_active
   expression: Link_previous_p - Link_p <= Link_ramp_down_allowance
 ```
 
 ```math
-\overleftarrow{f}_{\xi,t,l} - f_{\xi,t,l} \le \Delta^{f,-}_{\xi,t,l} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \left( \mathrm{rd}^{f}_{\xi,t,l} \text{ is defined} \vee \mathrm{rd}^{f,\mathrm{dn}}_{\xi,l} \text{ is defined} \right) \wedge \neg \left( \mathrm{com}^{f}_{l} \wedge \mathrm{ext}^{f}_{l} \wedge \neg \left( \mathrm{f}^{\mathrm{mod}}_{l} > 0 \right) \right) \wedge \left( \mathrm{pos}_{\mathrm{snapshot\_period}(t)}(t) > 0 \vee \mathrm{pos}(t) = 0 \wedge \left( \mathrm{u}^{f,0}_{\xi,l} = 0 \vee \mathrm{f}^{0}_{\xi,l} \text{ is defined} \right) \right) \wedge \mathrm{on}^{f}_{t,l}
+\overleftarrow{f}_{\xi,t,l} - f_{\xi,t,l} \le \Delta^{f,-}_{\xi,t,l} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \left( \mathrm{rd}^{f}_{\xi,t,l} \text{ is defined} \vee \mathrm{rd}^{f,\mathrm{dn}}_{\xi,l} \text{ is defined} \right) \wedge \neg \left( \mathrm{com}^{f}_{l} \wedge \mathrm{ext}^{f}_{l} \wedge \neg \left( \mathrm{f}^{\mathrm{mod}}_{l} > 0 \right) \right) \wedge \mathrm{prev}^{f}_{\xi,t,l} \wedge \mathrm{on}^{f}_{t,l}
 ```
 
 ### `Process-p-ramp_limit_up`
@@ -9143,13 +9128,13 @@ Process_p_ramp_limit_up:
   where: >-
     (Process_ramp_limit_up OR Process_ramp_limit_start_up)
     AND NOT (Process_committable AND Process_p_nom_extendable AND NOT (Process_p_nom_mod > 0))
-    AND (position(snapshot, within=snapshot_period[period]) > 0 OR (position(snapshot) == 0 AND (Process_status_initial == 0 OR Process_p_init)))
+    AND Process_ramps_from_previous
     AND Process_active
   expression: Process_p - Process_previous_p <= Process_ramp_up_allowance
 ```
 
 ```math
-z_{\xi,t,j} - \overleftarrow{z}_{\xi,t,j} \le \Delta^{z,+}_{\xi,t,j} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \left( \mathrm{ru}^{z}_{\xi,t,j} \text{ is defined} \vee \mathrm{ru}^{z,\mathrm{up}}_{\xi,j} \text{ is defined} \right) \wedge \neg \left( \mathrm{com}^{z}_{j} \wedge \mathrm{ext}^{z}_{j} \wedge \neg \left( \mathrm{z}^{\mathrm{mod}}_{j} > 0 \right) \right) \wedge \left( \mathrm{pos}_{\mathrm{snapshot\_period}(t)}(t) > 0 \vee \mathrm{pos}(t) = 0 \wedge \left( \mathrm{u}^{z,0}_{\xi,j} = 0 \vee \mathrm{z}^{0}_{\xi,j} \text{ is defined} \right) \right) \wedge \mathrm{on}^{z}_{t,j}
+z_{\xi,t,j} - \overleftarrow{z}_{\xi,t,j} \le \Delta^{z,+}_{\xi,t,j} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \left( \mathrm{ru}^{z}_{\xi,t,j} \text{ is defined} \vee \mathrm{ru}^{z,\mathrm{up}}_{\xi,j} \text{ is defined} \right) \wedge \neg \left( \mathrm{com}^{z}_{j} \wedge \mathrm{ext}^{z}_{j} \wedge \neg \left( \mathrm{z}^{\mathrm{mod}}_{j} > 0 \right) \right) \wedge \mathrm{prev}^{z}_{\xi,t,j} \wedge \mathrm{on}^{z}_{t,j}
 ```
 
 ### `Process-p-ramp_limit_down`
@@ -9169,13 +9154,13 @@ Process_p_ramp_limit_down:
   where: >-
     (Process_ramp_limit_down OR Process_ramp_limit_shut_down)
     AND NOT (Process_committable AND Process_p_nom_extendable AND NOT (Process_p_nom_mod > 0))
-    AND (position(snapshot, within=snapshot_period[period]) > 0 OR (position(snapshot) == 0 AND (Process_status_initial == 0 OR Process_p_init)))
+    AND Process_ramps_from_previous
     AND Process_active
   expression: Process_previous_p - Process_p <= Process_ramp_down_allowance
 ```
 
 ```math
-\overleftarrow{z}_{\xi,t,j} - z_{\xi,t,j} \le \Delta^{z,-}_{\xi,t,j} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \left( \mathrm{rd}^{z}_{\xi,t,j} \text{ is defined} \vee \mathrm{rd}^{z,\mathrm{dn}}_{\xi,j} \text{ is defined} \right) \wedge \neg \left( \mathrm{com}^{z}_{j} \wedge \mathrm{ext}^{z}_{j} \wedge \neg \left( \mathrm{z}^{\mathrm{mod}}_{j} > 0 \right) \right) \wedge \left( \mathrm{pos}_{\mathrm{snapshot\_period}(t)}(t) > 0 \vee \mathrm{pos}(t) = 0 \wedge \left( \mathrm{u}^{z,0}_{\xi,j} = 0 \vee \mathrm{z}^{0}_{\xi,j} \text{ is defined} \right) \right) \wedge \mathrm{on}^{z}_{t,j}
+\overleftarrow{z}_{\xi,t,j} - z_{\xi,t,j} \le \Delta^{z,-}_{\xi,t,j} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \left( \mathrm{rd}^{z}_{\xi,t,j} \text{ is defined} \vee \mathrm{rd}^{z,\mathrm{dn}}_{\xi,j} \text{ is defined} \right) \wedge \neg \left( \mathrm{com}^{z}_{j} \wedge \mathrm{ext}^{z}_{j} \wedge \neg \left( \mathrm{z}^{\mathrm{mod}}_{j} > 0 \right) \right) \wedge \mathrm{prev}^{z}_{\xi,t,j} \wedge \mathrm{on}^{z}_{t,j}
 ```
 
 ### `StorageUnit-ext-p_dispatch-lower`
@@ -9186,12 +9171,12 @@ Process_p_ramp_limit_down:
 StorageUnit_ext_p_dispatch_lower:
   description: "`StorageUnit-ext-p_dispatch-lower` — dispatch is non-negative"
   dims: [scenario, snapshot, storage_unit]
-  where: StorageUnit_p_nom_extendable AND StorageUnit_active
+  where: StorageUnit_ext
   expression: StorageUnit_p_dispatch >= 0
 ```
 
 ```math
-h^{+}_{\xi,t,s} \ge 0 \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ s \in \mathcal{S} \,:\, \mathrm{ext}^{h}_{s} \wedge \mathrm{on}^{h}_{t,s}
+h^{+}_{\xi,t,s} \ge 0 \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ s \in \mathcal{S} \,:\, \mathrm{on}^{h,\mathrm{ext}}_{t,s}
 ```
 
 ### `StorageUnit-ext-p_dispatch-upper`
@@ -9202,12 +9187,12 @@ h^{+}_{\xi,t,s} \ge 0 \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ s \in \
 StorageUnit_ext_p_dispatch_upper:
   description: "`StorageUnit-ext-p_dispatch-upper` — an extendable unit dispatches at most the chosen build"
   dims: [scenario, snapshot, storage_unit]
-  where: StorageUnit_p_nom_extendable AND StorageUnit_active
+  where: StorageUnit_ext
   expression: StorageUnit_p_dispatch <= StorageUnit_p_max_pu * StorageUnit_p_nom_ext
 ```
 
 ```math
-h^{+}_{\xi,t,s} \le \overline{\mathrm{h}}_{\xi,t,s} \cdot H_{s} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ s \in \mathcal{S} \,:\, \mathrm{ext}^{h}_{s} \wedge \mathrm{on}^{h}_{t,s}
+h^{+}_{\xi,t,s} \le \overline{\mathrm{h}}_{\xi,t,s} \cdot H_{s} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ s \in \mathcal{S} \,:\, \mathrm{on}^{h,\mathrm{ext}}_{t,s}
 ```
 
 ### `StorageUnit-ext-p_store-lower`
@@ -9218,12 +9203,12 @@ h^{+}_{\xi,t,s} \le \overline{\mathrm{h}}_{\xi,t,s} \cdot H_{s} \qquad \forall\,
 StorageUnit_ext_p_store_lower:
   description: "`StorageUnit-ext-p_store-lower` — storing is non-negative"
   dims: [scenario, snapshot, storage_unit]
-  where: StorageUnit_p_nom_extendable AND StorageUnit_active
+  where: StorageUnit_ext
   expression: StorageUnit_p_store >= 0
 ```
 
 ```math
-h^{-}_{\xi,t,s} \ge 0 \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ s \in \mathcal{S} \,:\, \mathrm{ext}^{h}_{s} \wedge \mathrm{on}^{h}_{t,s}
+h^{-}_{\xi,t,s} \ge 0 \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ s \in \mathcal{S} \,:\, \mathrm{on}^{h,\mathrm{ext}}_{t,s}
 ```
 
 ### `StorageUnit-ext-p_store-upper`
@@ -9236,12 +9221,12 @@ StorageUnit_ext_p_store_upper:
     `StorageUnit-ext-p_store-upper` — an extendable unit stores at most the
     chosen build, the minimum-per-unit column carrying that cap negated
   dims: [scenario, snapshot, storage_unit]
-  where: StorageUnit_p_nom_extendable AND StorageUnit_active
+  where: StorageUnit_ext
   expression: StorageUnit_p_store <= -StorageUnit_p_min_pu * StorageUnit_p_nom_ext
 ```
 
 ```math
-h^{-}_{\xi,t,s} \le -\underline{\mathrm{h}}_{\xi,t,s} \cdot H_{s} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ s \in \mathcal{S} \,:\, \mathrm{ext}^{h}_{s} \wedge \mathrm{on}^{h}_{t,s}
+h^{-}_{\xi,t,s} \le -\underline{\mathrm{h}}_{\xi,t,s} \cdot H_{s} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ s \in \mathcal{S} \,:\, \mathrm{on}^{h,\mathrm{ext}}_{t,s}
 ```
 
 ### `StorageUnit-ext-state_of_charge-lower`
@@ -9252,12 +9237,12 @@ h^{-}_{\xi,t,s} \le -\underline{\mathrm{h}}_{\xi,t,s} \cdot H_{s} \qquad \forall
 StorageUnit_ext_state_of_charge_lower:
   description: "`StorageUnit-ext-state_of_charge-lower` — charge is non-negative"
   dims: [scenario, snapshot, storage_unit]
-  where: StorageUnit_p_nom_extendable AND StorageUnit_active
+  where: StorageUnit_ext
   expression: StorageUnit_state_of_charge >= 0
 ```
 
 ```math
-\mathit{soc}_{\xi,t,s} \ge 0 \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ s \in \mathcal{S} \,:\, \mathrm{ext}^{h}_{s} \wedge \mathrm{on}^{h}_{t,s}
+\mathit{soc}_{\xi,t,s} \ge 0 \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ s \in \mathcal{S} \,:\, \mathrm{on}^{h,\mathrm{ext}}_{t,s}
 ```
 
 ### `StorageUnit-ext-state_of_charge-upper`
@@ -9268,12 +9253,12 @@ StorageUnit_ext_state_of_charge_lower:
 StorageUnit_ext_state_of_charge_upper:
   description: "`StorageUnit-ext-state_of_charge-upper` — an extendable unit holds at most its hours at the chosen build"
   dims: [scenario, snapshot, storage_unit]
-  where: StorageUnit_p_nom_extendable AND StorageUnit_active
+  where: StorageUnit_ext
   expression: StorageUnit_state_of_charge <= StorageUnit_max_hours * StorageUnit_p_nom_ext
 ```
 
 ```math
-\mathit{soc}_{\xi,t,s} \le \mathrm{T}^{h}_{\xi,s} \cdot H_{s} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ s \in \mathcal{S} \,:\, \mathrm{ext}^{h}_{s} \wedge \mathrm{on}^{h}_{t,s}
+\mathit{soc}_{\xi,t,s} \le \mathrm{T}^{h}_{\xi,s} \cdot H_{s} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ s \in \mathcal{S} \,:\, \mathrm{on}^{h,\mathrm{ext}}_{t,s}
 ```
 
 ### `StorageUnit-ext-p_nom-lower`
@@ -11716,19 +11701,19 @@ N_{g} \ge 0, N_{g} \in \mathbb{Z} \qquad \forall\, g \in \mathcal{G} \,:\, \math
 **`Generator_status`**
 
 ```math
-u_{\xi,t,g} \ge 0, u_{\xi,t,g} \in \mathbb{Z} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{com}_{g} \wedge \mathrm{on}_{t,g}
+u_{\xi,t,g} \ge 0, u_{\xi,t,g} \in \mathbb{Z} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{on}^{\mathrm{com}}_{t,g}
 ```
 
 **`Generator_start_up`**
 
 ```math
-\mathit{up}_{\xi,t,g} \ge 0, \mathit{up}_{\xi,t,g} \in \mathbb{Z} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{com}_{g} \wedge \mathrm{on}_{t,g}
+\mathit{up}_{\xi,t,g} \ge 0, \mathit{up}_{\xi,t,g} \in \mathbb{Z} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{on}^{\mathrm{com}}_{t,g}
 ```
 
 **`Generator_shut_down`**
 
 ```math
-\mathit{dn}_{\xi,t,g} \ge 0, \mathit{dn}_{\xi,t,g} \in \mathbb{Z} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{com}_{g} \wedge \mathrm{on}_{t,g}
+\mathit{dn}_{\xi,t,g} \ge 0, \mathit{dn}_{\xi,t,g} \in \mathbb{Z} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{on}^{\mathrm{com}}_{t,g}
 ```
 
 **`Generator_maintenance`**
@@ -11746,13 +11731,13 @@ u_{\xi,t,g} \ge 0, u_{\xi,t,g} \in \mathbb{Z} \qquad \forall\, \xi \in \Xi,\ t \
 **`Generator_maintenance_capacity`**
 
 ```math
-\mu^{\mathrm{nom}}_{\xi,t,g} \ge 0 \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{mnt}_{g} \wedge \mathrm{ext}_{g} \wedge \neg \left( \mathrm{com}_{g} \wedge \mathrm{p}^{\mathrm{mod}}_{g} > 0 \right) \wedge \mathrm{on}_{t,g}
+\mu^{\mathrm{nom}}_{\xi,t,g} \ge 0 \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{on}^{\mathrm{mnt,ext}}_{t,g}
 ```
 
 **`Generator_maintenance_status`**
 
 ```math
-\mu^{u}_{\xi,t,g} \ge 0 \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{mnt}_{g} \wedge \mathrm{com}_{g} \wedge \neg \left( \mathrm{ext}_{g} \wedge \neg \left( \mathrm{p}^{\mathrm{mod}}_{g} > 0 \right) \right) \wedge \mathrm{on}_{t,g}
+\mu^{u}_{\xi,t,g} \ge 0 \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{mnt}_{g} \wedge \mathrm{on}^{\mathrm{com}}_{t,g} \wedge \neg \left( \mathrm{ext}_{g} \wedge \neg \left( \mathrm{p}^{\mathrm{mod}}_{g} > 0 \right) \right)
 ```
 
 **`Link_n_mod`**
@@ -11764,19 +11749,19 @@ N^{f}_{l} \ge 0, N^{f}_{l} \in \mathbb{Z} \qquad \forall\, l \in \mathcal{L} \,:
 **`Link_status`**
 
 ```math
-u^{f}_{\xi,t,l} \ge 0, u^{f}_{\xi,t,l} \in \mathbb{Z} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{com}^{f}_{l} \wedge \mathrm{on}^{f}_{t,l}
+u^{f}_{\xi,t,l} \ge 0, u^{f}_{\xi,t,l} \in \mathbb{Z} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{on}^{f,\mathrm{com}}_{t,l}
 ```
 
 **`Link_start_up`**
 
 ```math
-\mathit{up}^{f}_{\xi,t,l} \ge 0, \mathit{up}^{f}_{\xi,t,l} \in \mathbb{Z} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{com}^{f}_{l} \wedge \mathrm{on}^{f}_{t,l}
+\mathit{up}^{f}_{\xi,t,l} \ge 0, \mathit{up}^{f}_{\xi,t,l} \in \mathbb{Z} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{on}^{f,\mathrm{com}}_{t,l}
 ```
 
 **`Link_shut_down`**
 
 ```math
-\mathit{dn}^{f}_{\xi,t,l} \ge 0, \mathit{dn}^{f}_{\xi,t,l} \in \mathbb{Z} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{com}^{f}_{l} \wedge \mathrm{on}^{f}_{t,l}
+\mathit{dn}^{f}_{\xi,t,l} \ge 0, \mathit{dn}^{f}_{\xi,t,l} \in \mathbb{Z} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{on}^{f,\mathrm{com}}_{t,l}
 ```
 
 **`Link_maintenance`**
@@ -11794,13 +11779,13 @@ u^{f}_{\xi,t,l} \ge 0, u^{f}_{\xi,t,l} \in \mathbb{Z} \qquad \forall\, \xi \in \
 **`Link_maintenance_capacity`**
 
 ```math
-\mu^{f,\mathrm{nom}}_{\xi,t,l} \ge 0 \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{mnt}^{f}_{l} \wedge \mathrm{ext}^{f}_{l} \wedge \neg \left( \mathrm{com}^{f}_{l} \wedge \mathrm{f}^{\mathrm{mod}}_{l} > 0 \right) \wedge \mathrm{on}^{f}_{t,l}
+\mu^{f,\mathrm{nom}}_{\xi,t,l} \ge 0 \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{on}^{f,\mathrm{mnt,ext}}_{t,l}
 ```
 
 **`Link_maintenance_status`**
 
 ```math
-\mu^{f,u}_{\xi,t,l} \ge 0 \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{mnt}^{f}_{l} \wedge \mathrm{com}^{f}_{l} \wedge \neg \left( \mathrm{ext}^{f}_{l} \wedge \neg \left( \mathrm{f}^{\mathrm{mod}}_{l} > 0 \right) \right) \wedge \mathrm{on}^{f}_{t,l}
+\mu^{f,u}_{\xi,t,l} \ge 0 \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{mnt}^{f}_{l} \wedge \mathrm{on}^{f,\mathrm{com}}_{t,l} \wedge \neg \left( \mathrm{ext}^{f}_{l} \wedge \neg \left( \mathrm{f}^{\mathrm{mod}}_{l} > 0 \right) \right)
 ```
 
 **`Process_n_mod`**
@@ -11812,19 +11797,19 @@ N^{z}_{j} \ge 0, N^{z}_{j} \in \mathbb{Z} \qquad \forall\, j \in \mathcal{J} \,:
 **`Process_status`**
 
 ```math
-u^{z}_{\xi,t,j} \ge 0, u^{z}_{\xi,t,j} \in \mathbb{Z} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{com}^{z}_{j} \wedge \mathrm{on}^{z}_{t,j}
+u^{z}_{\xi,t,j} \ge 0, u^{z}_{\xi,t,j} \in \mathbb{Z} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{on}^{z,\mathrm{com}}_{t,j}
 ```
 
 **`Process_start_up`**
 
 ```math
-\mathit{up}^{z}_{\xi,t,j} \ge 0, \mathit{up}^{z}_{\xi,t,j} \in \mathbb{Z} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{com}^{z}_{j} \wedge \mathrm{on}^{z}_{t,j}
+\mathit{up}^{z}_{\xi,t,j} \ge 0, \mathit{up}^{z}_{\xi,t,j} \in \mathbb{Z} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{on}^{z,\mathrm{com}}_{t,j}
 ```
 
 **`Process_shut_down`**
 
 ```math
-\mathit{dn}^{z}_{\xi,t,j} \ge 0, \mathit{dn}^{z}_{\xi,t,j} \in \mathbb{Z} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{com}^{z}_{j} \wedge \mathrm{on}^{z}_{t,j}
+\mathit{dn}^{z}_{\xi,t,j} \ge 0, \mathit{dn}^{z}_{\xi,t,j} \in \mathbb{Z} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{on}^{z,\mathrm{com}}_{t,j}
 ```
 
 **`Process_maintenance`**
@@ -11842,13 +11827,13 @@ u^{z}_{\xi,t,j} \ge 0, u^{z}_{\xi,t,j} \in \mathbb{Z} \qquad \forall\, \xi \in \
 **`Process_maintenance_capacity`**
 
 ```math
-\mu^{z,\mathrm{nom}}_{\xi,t,j} \ge 0 \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{mnt}^{z}_{j} \wedge \mathrm{ext}^{z}_{j} \wedge \neg \left( \mathrm{com}^{z}_{j} \wedge \mathrm{z}^{\mathrm{mod}}_{j} > 0 \right) \wedge \mathrm{on}^{z}_{t,j}
+\mu^{z,\mathrm{nom}}_{\xi,t,j} \ge 0 \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{on}^{z,\mathrm{mnt,ext}}_{t,j}
 ```
 
 **`Process_maintenance_status`**
 
 ```math
-\mu^{z,u}_{\xi,t,j} \ge 0 \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{mnt}^{z}_{j} \wedge \mathrm{com}^{z}_{j} \wedge \neg \left( \mathrm{ext}^{z}_{j} \wedge \neg \left( \mathrm{z}^{\mathrm{mod}}_{j} > 0 \right) \right) \wedge \mathrm{on}^{z}_{t,j}
+\mu^{z,u}_{\xi,t,j} \ge 0 \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{mnt}^{z}_{j} \wedge \mathrm{on}^{z,\mathrm{com}}_{t,j} \wedge \neg \left( \mathrm{ext}^{z}_{j} \wedge \neg \left( \mathrm{z}^{\mathrm{mod}}_{j} > 0 \right) \right)
 ```
 
 **`Line_s`**
@@ -11860,7 +11845,7 @@ s_{\xi,t,k} \in \mathbb{R} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ k
 **`Line_loss`**
 
 ```math
-\ell_{\xi,t,k} \ge 0 \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ k \in \mathcal{K} \,:\, \mathrm{lossy} \wedge \mathrm{on}^{s}_{t,k}
+\ell_{\xi,t,k} \ge 0 \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ k \in \mathcal{K} \,:\, \mathrm{on}^{s,\mathrm{lossy}}_{t,k}
 ```
 
 **`Transformer_s`**
@@ -11872,7 +11857,7 @@ s_{\xi,t,k} \in \mathbb{R} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ k
 **`Transformer_loss`**
 
 ```math
-\ell^{\sigma}_{\xi,t,m} \ge 0 \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ m \in \mathcal{M} \,:\, \mathrm{lossy} \wedge \mathrm{on}^{\sigma}_{t,m}
+\ell^{\sigma}_{\xi,t,m} \ge 0 \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ m \in \mathcal{M} \,:\, \mathrm{on}^{\sigma,\mathrm{lossy}}_{t,m}
 ```
 
 **`Transformer_phase_shift`**
diff --git a/docs/examples/pypsa/generator.md b/docs/examples/pypsa/generator.md
index f2a67033..381b0a7e 100644
--- a/docs/examples/pypsa/generator.md
+++ b/docs/examples/pypsa/generator.md
@@ -222,6 +222,13 @@ expressions:
     expression: sum(Generator_sign * Generator_p, over=generator, by=Generator_bus[bus])
     adds_to: Bus_injection
 
+masks:
+  Generator_committed:
+    description: >-
+      a committable generator that stands in the snapshot's period — every
+      unit-commitment row's set
+    where: Generator_committable AND Generator_active
+
 constraints:
   Generator_fix_p_lower:
     description: "`Generator-fix-p-lower` — a fixed generator outputs at least its minimum"
@@ -374,6 +381,12 @@ assumptions:
 | $`\mathit{Generator\_additions}`$ | `Generator_additions` over $`\mathcal{Y} \times \mathcal{I}`$ |
 | $`\mathit{Generator\_injection}`$ | `Generator_injection` over $`\Xi \times \mathcal{T} \times \mathcal{N}`$ |
 
+#### Masks
+
+| Symbol | Meaning |
+|---|---|
+| $`\mathrm{on}^{\mathrm{com}}`$ | `Generator_committed` over $`\mathcal{T} \times \mathcal{G}`$ — a committable generator that stands in the snapshot's period — every unit-commitment row's set |
+
 #### Subject to
 
 **`Generator_fix_p_lower`**
@@ -498,6 +511,14 @@ p_{\xi,t,g} = \mathrm{p}^{\mathrm{set}}_{\xi,t,g} \qquad \forall\, \xi \in \Xi,\
 \mathit{Generator\_injection}_{\xi,t,n} = \sum_{g \in \mathcal{G} \,:\, \mathrm{Generator\_bus}(g) = n} \mathrm{sgn}_{g} \cdot p_{\xi,t,g} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ n \in \mathcal{N}
 ```
 
+#### Masks
+
+**`Generator_committed`**
+
+```math
+\mathrm{on}^{\mathrm{com}}_{t,g} \iff \mathrm{com}_{g} \wedge \mathrm{on}_{t,g} \qquad \forall\, t \in \mathcal{T},\ g \in \mathcal{G}
+```
+
 #### Variable domains
 
 **`Generator_p`**
diff --git a/docs/examples/pypsa/generator_commitment.md b/docs/examples/pypsa/generator_commitment.md
index aa3ab50c..bc6be516 100644
--- a/docs/examples/pypsa/generator_commitment.md
+++ b/docs/examples/pypsa/generator_commitment.md
@@ -88,21 +88,21 @@ variables:
       the rows below cap at one, or at the module count where the build is
       modular
     dims: [scenario, snapshot, generator]
-    where: Generator_committable AND Generator_active
+    where: Generator_committed
     domain: integer
     bounds:
       lower: 0
   Generator_start_up:
     description: "`Generator-start_up` — how much of a committable unit turns on this snapshot, capped as the status is"
     dims: [scenario, snapshot, generator]
-    where: Generator_committable AND Generator_active
+    where: Generator_committed
     domain: integer
     bounds:
       lower: 0
   Generator_shut_down:
     description: "`Generator-shut_down` — how much of a committable unit turns off this snapshot, capped as the status is"
     dims: [scenario, snapshot, generator]
-    where: Generator_committable AND Generator_active
+    where: Generator_committed
     domain: integer
     bounds:
       lower: 0
@@ -128,6 +128,8 @@ given:
     Generator_p_nom_ext: { dims: [generator] }
   expressions:
     scenario_opex: { dims: [scenario] }
+  masks:
+    Generator_committed: { dims: [snapshot, generator] }
 
 expressions:
   Generator_previous_status:
@@ -155,26 +157,38 @@ expressions:
       + sum(sum(Generator_shut_down * Generator_shut_down_cost, over=generator), over=snapshot)
     adds_to: scenario_opex
 
+masks:
+  Generator_com_ext:
+    description: >-
+      a committable generator with an extendable, non-modular build that
+      stands in the snapshot's period — PyPSA's `com-ext` rows, whose status
+      is relaxed against the chosen build
+    where: >-
+      Generator_committable
+      AND Generator_p_nom_extendable
+      AND NOT (Generator_p_nom_mod > 0)
+      AND Generator_active
+
 constraints:
   Generator_com_p_lower:
     description: "`Generator-com-p-lower` — a committed unit outputs at least its minimum; off, at least nothing"
     dims: [scenario, snapshot, generator]
-    where: Generator_committable AND not Generator_p_nom_extendable AND NOT (Generator_p_nom_mod > 0) AND Generator_active
+    where: Generator_committed AND NOT Generator_p_nom_extendable AND NOT (Generator_p_nom_mod > 0)
     expression: Generator_p >= Generator_p_min_pu * Generator_p_nom * (Generator_status - Generator_maintenance_pu * Generator_maintenance_status)
   Generator_com_p_upper:
     description: "`Generator-com-p-upper` — a committed unit outputs at most what is available; off, at most nothing"
     dims: [scenario, snapshot, generator]
-    where: Generator_committable AND not Generator_p_nom_extendable AND NOT (Generator_p_nom_mod > 0) AND Generator_active
+    where: Generator_committed AND NOT Generator_p_nom_extendable AND NOT (Generator_p_nom_mod > 0)
     expression: Generator_p <= Generator_p_max_pu * Generator_p_nom * (Generator_status - Generator_maintenance_pu * Generator_maintenance_status)
   Generator_com_transition_start_up:
     description: "`Generator-com-transition-start-up` — turning on is a start, counted against the state the unit carried into the snapshot"
     dims: [scenario, snapshot, generator]
-    where: Generator_committable AND Generator_active
+    where: Generator_committed
     expression: Generator_start_up >= Generator_status - Generator_previous_status
   Generator_com_transition_shut_down:
     description: "`Generator-com-transition-shut-down` — turning off is a stop, counted against the state the unit carried into the snapshot"
     dims: [scenario, snapshot, generator]
-    where: Generator_committable AND Generator_active
+    where: Generator_committed
     expression: Generator_shut_down >= Generator_previous_status - Generator_status
   Generator_com_up_time:
     description: >-
@@ -182,7 +196,7 @@ constraints:
       is still on. The first snapshot's share of the window is the brought-in
       up time's, which the must-stay-up mask carries
     dims: [scenario, snapshot, generator]
-    where: Generator_committable AND Generator_min_up_time > 0 AND position(snapshot) > 0 AND Generator_active
+    where: Generator_committed AND Generator_min_up_time > 0 AND position(snapshot) > 0
     expression: sum_back(Generator_start_up, along=snapshot, window=Generator_min_up_time) <= Generator_status
   Generator_com_down_time:
     description: >-
@@ -190,38 +204,38 @@ constraints:
       time is still off. The first snapshot's share of the window is the
       brought-in down time's, which the must-stay-down mask carries
     dims: [scenario, snapshot, generator]
-    where: Generator_committable AND Generator_min_down_time > 0 AND position(snapshot) > 0 AND Generator_active
+    where: Generator_committed AND Generator_min_down_time > 0 AND position(snapshot) > 0
     expression: sum_back(Generator_shut_down, along=snapshot, window=Generator_min_down_time) <= 1 - Generator_status
   Generator_com_status_must_stay_up:
     description: "`Generator-com-status-min_up_time_must_stay_up` — a unit still serving the up time it brought in stays on"
     dims: [scenario, snapshot, generator]
-    where: Generator_committable AND Generator_must_stay_up AND Generator_active
+    where: Generator_committed AND Generator_must_stay_up
     expression: Generator_status == 1
   Generator_com_status_must_stay_down:
     description: >-
       `Generator-com-status-min_down_time_must_stay_up` — a unit still serving
       the down time it brought in stays off; PyPSA names the row `_must_stay_up`
     dims: [scenario, snapshot, generator]
-    where: Generator_committable AND Generator_must_stay_down AND Generator_active
+    where: Generator_committed AND Generator_must_stay_down
     expression: Generator_status == 0
   Generator_com_ext_p_upper_cap:
     description: >-
       `Generator-com-ext-p-upper-cap` — a committed extendable unit outputs
       at most what is available of the chosen build, whatever its status
     dims: [scenario, snapshot, generator]
-    where: Generator_committable AND Generator_p_nom_extendable AND NOT (Generator_p_nom_mod > 0) AND Generator_active
+    where: Generator_com_ext
     expression: Generator_p <= Generator_p_max_pu * (Generator_p_nom_ext - Generator_maintenance_pu * Generator_maintenance_capacity)
   Generator_com_ext_p_upper_big_m:
     description: "`Generator-com-ext-p-upper-bigM` — off, a unit outputs nothing; on, the big M is no bound"
     dims: [scenario, snapshot, generator]
-    where: Generator_committable AND Generator_p_nom_extendable AND NOT (Generator_p_nom_mod > 0) AND Generator_active
+    where: Generator_com_ext
     expression: Generator_p <= Generator_big_m * Generator_status
   Generator_com_ext_p_lower:
     description: >-
       `Generator-com-ext-p-lower` — a committed extendable unit outputs at
       least its minimum of the chosen build; off, the big M releases the row
     dims: [scenario, snapshot, generator]
-    where: Generator_committable AND Generator_p_nom_extendable AND NOT (Generator_p_nom_mod > 0) AND Generator_active
+    where: Generator_com_ext
     expression: >-
       Generator_p >=
       Generator_p_min_pu * (Generator_p_nom_ext - Generator_maintenance_pu * Generator_maintenance_capacity)
@@ -232,23 +246,21 @@ constraints:
       negative, output is also plainly non-negative, a row the big-M lower
       cannot assert while the unit is off
     dims: [scenario, snapshot, generator]
-    where: >-
-      Generator_committable AND Generator_p_nom_extendable
-      AND Generator_p_min_pu_nonneg AND NOT (Generator_p_nom_mod > 0) AND Generator_active
+    where: Generator_com_ext AND Generator_p_min_pu_nonneg
     expression: Generator_p >= 0
   Generator_com_mod_p_lower:
     description: >-
       `Generator-com-mod-p-lower` — a committed modular unit outputs at least
       its minimum of one module, whether the build is fixed or a decision
     dims: [scenario, snapshot, generator]
-    where: Generator_committable AND Generator_p_nom_mod > 0 AND Generator_active
+    where: Generator_committed AND Generator_p_nom_mod > 0
     expression: Generator_p >= Generator_p_min_pu * Generator_p_nom_mod * (Generator_status - Generator_maintenance_pu * Generator_maintenance_status)
   Generator_com_mod_p_upper:
     description: >-
       `Generator-com-mod-p-upper` — a committed modular unit outputs at most
       one module's share, whether the build is fixed or a decision
     dims: [scenario, snapshot, generator]
-    where: Generator_committable AND Generator_p_nom_mod > 0 AND Generator_active
+    where: Generator_committed AND Generator_p_nom_mod > 0
     expression: Generator_p <= Generator_p_max_pu * Generator_p_nom_mod * (Generator_status - Generator_maintenance_pu * Generator_maintenance_status)
   Generator_status_p_fixed_upper:
     description: >-
@@ -256,7 +268,7 @@ constraints:
       place, an explicit row as PyPSA writes it: one where the build is not
       modular, and the fixed build's whole count of modules where it is
     dims: [scenario, snapshot, generator]
-    where: Generator_committable AND NOT (Generator_p_nom_extendable AND Generator_p_nom_mod > 0) AND Generator_active
+    where: Generator_committed AND NOT (Generator_p_nom_extendable AND Generator_p_nom_mod > 0)
     expression: Generator_status <= Generator_modules_installed
   Generator_start_up_p_fixed_upper:
     description: >-
@@ -264,7 +276,7 @@ constraints:
       place, an explicit row as PyPSA writes it: one where the build is not
       modular, and the fixed build's whole count of modules where it is
     dims: [scenario, snapshot, generator]
-    where: Generator_committable AND NOT (Generator_p_nom_extendable AND Generator_p_nom_mod > 0) AND Generator_active
+    where: Generator_committed AND NOT (Generator_p_nom_extendable AND Generator_p_nom_mod > 0)
     expression: Generator_start_up <= Generator_modules_installed
   Generator_shut_down_p_fixed_upper:
     description: >-
@@ -272,22 +284,22 @@ constraints:
       place, an explicit row as PyPSA writes it: one where the build is not
       modular, and the fixed build's whole count of modules where it is
     dims: [scenario, snapshot, generator]
-    where: Generator_committable AND NOT (Generator_p_nom_extendable AND Generator_p_nom_mod > 0) AND Generator_active
+    where: Generator_committed AND NOT (Generator_p_nom_extendable AND Generator_p_nom_mod > 0)
     expression: Generator_shut_down <= Generator_modules_installed
   Generator_status_p_nom_variable_upper:
     description: "`Generator-status-p_nom-variable-upper` — a modular unit is on only where a module is built"
     dims: [scenario, snapshot, generator]
-    where: Generator_committable AND Generator_p_nom_extendable AND Generator_p_nom_mod > 0 AND Generator_active
+    where: Generator_committed AND Generator_p_nom_extendable AND Generator_p_nom_mod > 0
     expression: Generator_status <= Generator_n_mod
   Generator_start_up_p_nom_variable_upper:
     description: "`Generator-start_up-p_nom-variable-upper` — a modular unit starts only where a module is built"
     dims: [scenario, snapshot, generator]
-    where: Generator_committable AND Generator_p_nom_extendable AND Generator_p_nom_mod > 0 AND Generator_active
+    where: Generator_committed AND Generator_p_nom_extendable AND Generator_p_nom_mod > 0
     expression: Generator_start_up <= Generator_n_mod
   Generator_shut_down_p_nom_variable_upper:
     description: "`Generator-shut_down-p_nom-variable-upper` — a modular unit stops only where a module is built"
     dims: [scenario, snapshot, generator]
-    where: Generator_committable AND Generator_p_nom_extendable AND Generator_p_nom_mod > 0 AND Generator_active
+    where: Generator_committed AND Generator_p_nom_extendable AND Generator_p_nom_mod > 0
     expression: Generator_shut_down <= Generator_n_mod
 ```
 
@@ -344,6 +356,7 @@ constraints:
 | $`\mu^{u}`$ | `Generator_maintenance_status` over $`\Xi \times \mathcal{T} \times \mathcal{G}`$ |
 | $`P`$ | `Generator_p_nom_ext` over $`\mathcal{G}`$ |
 | $`\mathit{scenario\_opex}`$ | `scenario_opex` over $`\Xi`$, an expression this file adds `Generator_commitment_opex` to |
+| $`\mathrm{on}^{\mathrm{com}}`$ | `Generator_committed` over $`\mathcal{T} \times \mathcal{G}`$, a mask another file defines |
 
 #### Definitions
 
@@ -353,6 +366,12 @@ constraints:
 | $`\overleftarrow{u}^{\circ}`$ | `Generator_status_carried_over` over $`\Xi \times \mathcal{T} \times \mathcal{G}`$ — the state a generator carries over into a snapshot — the state it brought into the horizon at the first, the previous snapshot's after that |
 | $`\mathit{Generator\_commitment\_opex}`$ | `Generator_commitment_opex` over $`\Xi`$ |
 
+#### Masks
+
+| Symbol | Meaning |
+|---|---|
+| $`\mathrm{on}^{\mathrm{com,ext}}`$ | `Generator_com_ext` over $`\mathcal{T} \times \mathcal{G}`$ — a committable generator with an extendable, non-modular build that stands in the snapshot's period — PyPSA's `com-ext` rows, whose status is relaxed against the chosen build |
+
 $`\mathrm{pos}(t)`$ denotes where index $`t`$ sits along its dimension's own order — the order `shift` steps along, not the order labels sort in — counted from $`0`$. The index itself stays the coordinate, so $`t`$ compares against labels and $`\mathrm{pos}(t)`$ against positions.
 
 #### Subject to
@@ -360,121 +379,121 @@ $`\mathrm{pos}(t)`$ denotes where index $`t`$ sits along its dimension's own ord
 **`Generator_com_p_lower`**
 
 ```math
-p_{\xi,t,g} \ge \underline{\mathrm{p}}_{\xi,t,g} \cdot \mathrm{p}^{\mathrm{nom}}_{\xi,g} \cdot \left( u_{\xi,t,g} - \gamma_{\xi,g} \cdot \mu^{u}_{\xi,t,g} \right) \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{com}_{g} \wedge \neg \mathrm{ext}_{g} \wedge \neg \left( \mathrm{p}^{\mathrm{mod}}_{g} > 0 \right) \wedge \mathrm{on}_{t,g}
+p_{\xi,t,g} \ge \underline{\mathrm{p}}_{\xi,t,g} \cdot \mathrm{p}^{\mathrm{nom}}_{\xi,g} \cdot \left( u_{\xi,t,g} - \gamma_{\xi,g} \cdot \mu^{u}_{\xi,t,g} \right) \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{on}^{\mathrm{com}}_{t,g} \wedge \neg \mathrm{ext}_{g} \wedge \neg \left( \mathrm{p}^{\mathrm{mod}}_{g} > 0 \right)
 ```
 
 **`Generator_com_p_upper`**
 
 ```math
-p_{\xi,t,g} \le \overline{\mathrm{p}}_{\xi,t,g} \cdot \mathrm{p}^{\mathrm{nom}}_{\xi,g} \cdot \left( u_{\xi,t,g} - \gamma_{\xi,g} \cdot \mu^{u}_{\xi,t,g} \right) \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{com}_{g} \wedge \neg \mathrm{ext}_{g} \wedge \neg \left( \mathrm{p}^{\mathrm{mod}}_{g} > 0 \right) \wedge \mathrm{on}_{t,g}
+p_{\xi,t,g} \le \overline{\mathrm{p}}_{\xi,t,g} \cdot \mathrm{p}^{\mathrm{nom}}_{\xi,g} \cdot \left( u_{\xi,t,g} - \gamma_{\xi,g} \cdot \mu^{u}_{\xi,t,g} \right) \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{on}^{\mathrm{com}}_{t,g} \wedge \neg \mathrm{ext}_{g} \wedge \neg \left( \mathrm{p}^{\mathrm{mod}}_{g} > 0 \right)
 ```
 
 **`Generator_com_transition_start_up`**
 
 ```math
-\mathit{up}_{\xi,t,g} \ge u_{\xi,t,g} - \overleftarrow{u}_{\xi,t,g} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{com}_{g} \wedge \mathrm{on}_{t,g}
+\mathit{up}_{\xi,t,g} \ge u_{\xi,t,g} - \overleftarrow{u}_{\xi,t,g} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{on}^{\mathrm{com}}_{t,g}
 ```
 
 **`Generator_com_transition_shut_down`**
 
 ```math
-\mathit{dn}_{\xi,t,g} \ge \overleftarrow{u}_{\xi,t,g} - u_{\xi,t,g} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{com}_{g} \wedge \mathrm{on}_{t,g}
+\mathit{dn}_{\xi,t,g} \ge \overleftarrow{u}_{\xi,t,g} - u_{\xi,t,g} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{on}^{\mathrm{com}}_{t,g}
 ```
 
 **`Generator_com_up_time`**
 
 ```math
-\sum_{t' \in \mathcal{T} \,:\, 0 \le t - t' < \mathrm{UT}} \mathit{up}_{\xi,t',g} \le u_{\xi,t,g} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{com}_{g} \wedge \mathrm{UT}_{\xi,g} > 0 \wedge \mathrm{pos}(t) > 0 \wedge \mathrm{on}_{t,g}
+\sum_{t' \in \mathcal{T} \,:\, 0 \le t - t' < \mathrm{UT}} \mathit{up}_{\xi,t',g} \le u_{\xi,t,g} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{on}^{\mathrm{com}}_{t,g} \wedge \mathrm{UT}_{\xi,g} > 0 \wedge \mathrm{pos}(t) > 0
 ```
 
 **`Generator_com_down_time`**
 
 ```math
-\sum_{t' \in \mathcal{T} \,:\, 0 \le t - t' < \mathrm{DT}} \mathit{dn}_{\xi,t',g} \le 1 - u_{\xi,t,g} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{com}_{g} \wedge \mathrm{DT}_{\xi,g} > 0 \wedge \mathrm{pos}(t) > 0 \wedge \mathrm{on}_{t,g}
+\sum_{t' \in \mathcal{T} \,:\, 0 \le t - t' < \mathrm{DT}} \mathit{dn}_{\xi,t',g} \le 1 - u_{\xi,t,g} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{on}^{\mathrm{com}}_{t,g} \wedge \mathrm{DT}_{\xi,g} > 0 \wedge \mathrm{pos}(t) > 0
 ```
 
 **`Generator_com_status_must_stay_up`**
 
 ```math
-u_{\xi,t,g} = 1 \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{com}_{g} \wedge \mathrm{hold}_{\xi,t,g} \wedge \mathrm{on}_{t,g}
+u_{\xi,t,g} = 1 \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{on}^{\mathrm{com}}_{t,g} \wedge \mathrm{hold}_{\xi,t,g}
 ```
 
 **`Generator_com_status_must_stay_down`**
 
 ```math
-u_{\xi,t,g} = 0 \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{com}_{g} \wedge \mathrm{rest}_{\xi,t,g} \wedge \mathrm{on}_{t,g}
+u_{\xi,t,g} = 0 \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{on}^{\mathrm{com}}_{t,g} \wedge \mathrm{rest}_{\xi,t,g}
 ```
 
 **`Generator_com_ext_p_upper_cap`**
 
 ```math
-p_{\xi,t,g} \le \overline{\mathrm{p}}_{\xi,t,g} \cdot \left( P_{g} - \gamma_{\xi,g} \cdot \mu^{\mathrm{nom}}_{\xi,t,g} \right) \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{com}_{g} \wedge \mathrm{ext}_{g} \wedge \neg \left( \mathrm{p}^{\mathrm{mod}}_{g} > 0 \right) \wedge \mathrm{on}_{t,g}
+p_{\xi,t,g} \le \overline{\mathrm{p}}_{\xi,t,g} \cdot \left( P_{g} - \gamma_{\xi,g} \cdot \mu^{\mathrm{nom}}_{\xi,t,g} \right) \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{on}^{\mathrm{com,ext}}_{t,g}
 ```
 
 **`Generator_com_ext_p_upper_big_m`**
 
 ```math
-p_{\xi,t,g} \le \mathrm{M}_{\xi,g} \cdot u_{\xi,t,g} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{com}_{g} \wedge \mathrm{ext}_{g} \wedge \neg \left( \mathrm{p}^{\mathrm{mod}}_{g} > 0 \right) \wedge \mathrm{on}_{t,g}
+p_{\xi,t,g} \le \mathrm{M}_{\xi,g} \cdot u_{\xi,t,g} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{on}^{\mathrm{com,ext}}_{t,g}
 ```
 
 **`Generator_com_ext_p_lower`**
 
 ```math
-p_{\xi,t,g} \ge \underline{\mathrm{p}}_{\xi,t,g} \cdot \left( P_{g} - \gamma_{\xi,g} \cdot \mu^{\mathrm{nom}}_{\xi,t,g} \right) + \mathrm{M}_{\xi,g} \cdot u_{\xi,t,g} - \mathrm{M}_{\xi,g} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{com}_{g} \wedge \mathrm{ext}_{g} \wedge \neg \left( \mathrm{p}^{\mathrm{mod}}_{g} > 0 \right) \wedge \mathrm{on}_{t,g}
+p_{\xi,t,g} \ge \underline{\mathrm{p}}_{\xi,t,g} \cdot \left( P_{g} - \gamma_{\xi,g} \cdot \mu^{\mathrm{nom}}_{\xi,t,g} \right) + \mathrm{M}_{\xi,g} \cdot u_{\xi,t,g} - \mathrm{M}_{\xi,g} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{on}^{\mathrm{com,ext}}_{t,g}
 ```
 
 **`Generator_com_ext_p_lower_nonneg`**
 
 ```math
-p_{\xi,t,g} \ge 0 \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{com}_{g} \wedge \mathrm{ext}_{g} \wedge \mathrm{nonneg}_{g} \wedge \neg \left( \mathrm{p}^{\mathrm{mod}}_{g} > 0 \right) \wedge \mathrm{on}_{t,g}
+p_{\xi,t,g} \ge 0 \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{on}^{\mathrm{com,ext}}_{t,g} \wedge \mathrm{nonneg}_{g}
 ```
 
 **`Generator_com_mod_p_lower`**
 
 ```math
-p_{\xi,t,g} \ge \underline{\mathrm{p}}_{\xi,t,g} \cdot \mathrm{p}^{\mathrm{mod}}_{g} \cdot \left( u_{\xi,t,g} - \gamma_{\xi,g} \cdot \mu^{u}_{\xi,t,g} \right) \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{com}_{g} \wedge \mathrm{p}^{\mathrm{mod}}_{g} > 0 \wedge \mathrm{on}_{t,g}
+p_{\xi,t,g} \ge \underline{\mathrm{p}}_{\xi,t,g} \cdot \mathrm{p}^{\mathrm{mod}}_{g} \cdot \left( u_{\xi,t,g} - \gamma_{\xi,g} \cdot \mu^{u}_{\xi,t,g} \right) \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{on}^{\mathrm{com}}_{t,g} \wedge \mathrm{p}^{\mathrm{mod}}_{g} > 0
 ```
 
 **`Generator_com_mod_p_upper`**
 
 ```math
-p_{\xi,t,g} \le \overline{\mathrm{p}}_{\xi,t,g} \cdot \mathrm{p}^{\mathrm{mod}}_{g} \cdot \left( u_{\xi,t,g} - \gamma_{\xi,g} \cdot \mu^{u}_{\xi,t,g} \right) \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{com}_{g} \wedge \mathrm{p}^{\mathrm{mod}}_{g} > 0 \wedge \mathrm{on}_{t,g}
+p_{\xi,t,g} \le \overline{\mathrm{p}}_{\xi,t,g} \cdot \mathrm{p}^{\mathrm{mod}}_{g} \cdot \left( u_{\xi,t,g} - \gamma_{\xi,g} \cdot \mu^{u}_{\xi,t,g} \right) \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{on}^{\mathrm{com}}_{t,g} \wedge \mathrm{p}^{\mathrm{mod}}_{g} > 0
 ```
 
 **`Generator_status_p_fixed_upper`**
 
 ```math
-u_{\xi,t,g} \le \mathrm{N}^{\mathrm{fix}}_{\xi,g} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{com}_{g} \wedge \neg \left( \mathrm{ext}_{g} \wedge \mathrm{p}^{\mathrm{mod}}_{g} > 0 \right) \wedge \mathrm{on}_{t,g}
+u_{\xi,t,g} \le \mathrm{N}^{\mathrm{fix}}_{\xi,g} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{on}^{\mathrm{com}}_{t,g} \wedge \neg \left( \mathrm{ext}_{g} \wedge \mathrm{p}^{\mathrm{mod}}_{g} > 0 \right)
 ```
 
 **`Generator_start_up_p_fixed_upper`**
 
 ```math
-\mathit{up}_{\xi,t,g} \le \mathrm{N}^{\mathrm{fix}}_{\xi,g} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{com}_{g} \wedge \neg \left( \mathrm{ext}_{g} \wedge \mathrm{p}^{\mathrm{mod}}_{g} > 0 \right) \wedge \mathrm{on}_{t,g}
+\mathit{up}_{\xi,t,g} \le \mathrm{N}^{\mathrm{fix}}_{\xi,g} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{on}^{\mathrm{com}}_{t,g} \wedge \neg \left( \mathrm{ext}_{g} \wedge \mathrm{p}^{\mathrm{mod}}_{g} > 0 \right)
 ```
 
 **`Generator_shut_down_p_fixed_upper`**
 
 ```math
-\mathit{dn}_{\xi,t,g} \le \mathrm{N}^{\mathrm{fix}}_{\xi,g} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{com}_{g} \wedge \neg \left( \mathrm{ext}_{g} \wedge \mathrm{p}^{\mathrm{mod}}_{g} > 0 \right) \wedge \mathrm{on}_{t,g}
+\mathit{dn}_{\xi,t,g} \le \mathrm{N}^{\mathrm{fix}}_{\xi,g} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{on}^{\mathrm{com}}_{t,g} \wedge \neg \left( \mathrm{ext}_{g} \wedge \mathrm{p}^{\mathrm{mod}}_{g} > 0 \right)
 ```
 
 **`Generator_status_p_nom_variable_upper`**
 
 ```math
-u_{\xi,t,g} \le N_{g} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{com}_{g} \wedge \mathrm{ext}_{g} \wedge \mathrm{p}^{\mathrm{mod}}_{g} > 0 \wedge \mathrm{on}_{t,g}
+u_{\xi,t,g} \le N_{g} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{on}^{\mathrm{com}}_{t,g} \wedge \mathrm{ext}_{g} \wedge \mathrm{p}^{\mathrm{mod}}_{g} > 0
 ```
 
 **`Generator_start_up_p_nom_variable_upper`**
 
 ```math
-\mathit{up}_{\xi,t,g} \le N_{g} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{com}_{g} \wedge \mathrm{ext}_{g} \wedge \mathrm{p}^{\mathrm{mod}}_{g} > 0 \wedge \mathrm{on}_{t,g}
+\mathit{up}_{\xi,t,g} \le N_{g} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{on}^{\mathrm{com}}_{t,g} \wedge \mathrm{ext}_{g} \wedge \mathrm{p}^{\mathrm{mod}}_{g} > 0
 ```
 
 **`Generator_shut_down_p_nom_variable_upper`**
 
 ```math
-\mathit{dn}_{\xi,t,g} \le N_{g} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{com}_{g} \wedge \mathrm{ext}_{g} \wedge \mathrm{p}^{\mathrm{mod}}_{g} > 0 \wedge \mathrm{on}_{t,g}
+\mathit{dn}_{\xi,t,g} \le N_{g} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{on}^{\mathrm{com}}_{t,g} \wedge \mathrm{ext}_{g} \wedge \mathrm{p}^{\mathrm{mod}}_{g} > 0
 ```
 
 #### Definitions
@@ -497,23 +516,31 @@ u_{\xi,t,g} \le N_{g} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \
 \mathit{Generator\_commitment\_opex}_{\xi} = \sum_{t \in \mathcal{T}} \sum_{g \in \mathcal{G}} u_{\xi,t,g} \cdot \mathrm{c}^{\mathrm{on}}_{\xi,t,g} \cdot \mathrm{w}_{t} \cdot \mathrm{w}^{y}_{\mathrm{snapshot\_period}(t)} + \sum_{t \in \mathcal{T}} \sum_{g \in \mathcal{G}} \mathit{up}_{\xi,t,g} \cdot \mathrm{c}^{\mathrm{up}}_{\xi,t,g} + \sum_{t \in \mathcal{T}} \sum_{g \in \mathcal{G}} \mathit{dn}_{\xi,t,g} \cdot \mathrm{c}^{\mathrm{dn}}_{\xi,t,g} \qquad \forall\, \xi \in \Xi
 ```
 
+#### Masks
+
+**`Generator_com_ext`**
+
+```math
+\mathrm{on}^{\mathrm{com,ext}}_{t,g} \iff \mathrm{com}_{g} \wedge \mathrm{ext}_{g} \wedge \neg \left( \mathrm{p}^{\mathrm{mod}}_{g} > 0 \right) \wedge \mathrm{on}_{t,g} \qquad \forall\, t \in \mathcal{T},\ g \in \mathcal{G}
+```
+
 #### Variable domains
 
 **`Generator_status`**
 
 ```math
-u_{\xi,t,g} \ge 0, u_{\xi,t,g} \in \mathbb{Z} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{com}_{g} \wedge \mathrm{on}_{t,g}
+u_{\xi,t,g} \ge 0, u_{\xi,t,g} \in \mathbb{Z} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{on}^{\mathrm{com}}_{t,g}
 ```
 
 **`Generator_start_up`**
 
 ```math
-\mathit{up}_{\xi,t,g} \ge 0, \mathit{up}_{\xi,t,g} \in \mathbb{Z} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{com}_{g} \wedge \mathrm{on}_{t,g}
+\mathit{up}_{\xi,t,g} \ge 0, \mathit{up}_{\xi,t,g} \in \mathbb{Z} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{on}^{\mathrm{com}}_{t,g}
 ```
 
 **`Generator_shut_down`**
 
 ```math
-\mathit{dn}_{\xi,t,g} \ge 0, \mathit{dn}_{\xi,t,g} \in \mathbb{Z} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{com}_{g} \wedge \mathrm{on}_{t,g}
+\mathit{dn}_{\xi,t,g} \ge 0, \mathit{dn}_{\xi,t,g} \in \mathbb{Z} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{on}^{\mathrm{com}}_{t,g}
 ```
 <!-- gallery:end -->
diff --git a/docs/examples/pypsa/generator_maintenance.md b/docs/examples/pypsa/generator_maintenance.md
index 09f731f6..7e293796 100644
--- a/docs/examples/pypsa/generator_maintenance.md
+++ b/docs/examples/pypsa/generator_maintenance.md
@@ -82,9 +82,7 @@ variables:
       `Generator-maintenance_capacity` — the chosen build while in maintenance, zero
       otherwise: the product the `maintcap` rows linearize
     dims: [scenario, snapshot, generator]
-    where: >-
-      Generator_maintainable AND Generator_p_nom_extendable
-      AND NOT (Generator_committable AND Generator_p_nom_mod > 0) AND Generator_active
+    where: Generator_maint_ext
     absence: zero
     bounds:
       lower: 0
@@ -95,8 +93,9 @@ variables:
       maintenance may also be off
     dims: [scenario, snapshot, generator]
     where: >-
-      Generator_maintainable AND Generator_committable
-      AND NOT (Generator_p_nom_extendable AND NOT (Generator_p_nom_mod > 0)) AND Generator_active
+      Generator_maintainable
+      AND Generator_committed
+      AND NOT (Generator_p_nom_extendable AND NOT (Generator_p_nom_mod > 0))
     absence: zero
     bounds:
       lower: 0
@@ -113,6 +112,20 @@ given:
   variables:
     Generator_status: { dims: [scenario, snapshot, generator], domain: integer }
     Generator_p_nom_ext: { dims: [generator] }
+  masks:
+    Generator_committed: { dims: [snapshot, generator] }
+
+masks:
+  Generator_maint_ext:
+    description: >-
+      a maintainable generator with an extendable build, unless it is
+      committable and modular, that stands in the snapshot's period — the
+      maintenance rows against the chosen build
+    where: >-
+      Generator_maintainable
+      AND Generator_p_nom_extendable
+      AND NOT (Generator_committable AND Generator_p_nom_mod > 0)
+      AND Generator_active
 
 constraints:
   Generator_maint_event_count:
@@ -138,54 +151,54 @@ constraints:
       `Generator-maintcap_upper` — the build taken off is at most the chosen build in
       maintenance, and at most the build less its floor out of it
     dims: [scenario, snapshot, generator]
-    where: Generator_maintainable AND Generator_p_nom_extendable AND NOT (Generator_committable AND Generator_p_nom_mod > 0) AND Generator_active
+    where: Generator_maint_ext
     expression: Generator_maintenance_capacity <= Generator_p_nom_ext - Generator_p_nom_min * (1 - Generator_maintenance)
   Generator_maintcap_upper_nommax:
     description: "`Generator-maintcap_upper_nommax` — out of maintenance, no build is taken off"
     dims: [scenario, snapshot, generator]
-    where: Generator_maintainable AND Generator_p_nom_extendable AND NOT (Generator_committable AND Generator_p_nom_mod > 0) AND Generator_active
+    where: Generator_maint_ext
     expression: Generator_maintenance_capacity <= Generator_p_nom_max * Generator_maintenance
   Generator_maintcap_lower_nommax:
     description: "`Generator-maintcap_lower_nommax` — in maintenance, the whole chosen build is taken off"
     dims: [scenario, snapshot, generator]
-    where: Generator_maintainable AND Generator_p_nom_extendable AND NOT (Generator_committable AND Generator_p_nom_mod > 0) AND Generator_active
+    where: Generator_maint_ext
     expression: Generator_maintenance_capacity >= Generator_p_nom_ext - Generator_p_nom_max * (1 - Generator_maintenance)
   Generator_maintcap_lower_nommin:
     description: "`Generator-maintcap_lower_nommin` — in maintenance, at least the floor of the build is taken off"
     dims: [scenario, snapshot, generator]
-    where: Generator_maintainable AND Generator_p_nom_extendable AND NOT (Generator_committable AND Generator_p_nom_mod > 0) AND Generator_active AND Generator_p_nom_min > 0
+    where: Generator_maint_ext AND Generator_p_nom_min > 0
     expression: Generator_maintenance_capacity >= Generator_p_nom_min * Generator_maintenance
   Generator_maint_status_le_status:
     description: "`Generator-maint-status-le-status` — the status in maintenance is at most the status"
     dims: [scenario, snapshot, generator]
-    where: Generator_maintainable AND Generator_committable AND NOT Generator_p_nom_extendable AND NOT (Generator_p_nom_mod > 0) AND Generator_active
+    where: Generator_maintainable AND Generator_committed AND NOT Generator_p_nom_extendable AND NOT (Generator_p_nom_mod > 0)
     expression: Generator_maintenance_status <= Generator_status
   Generator_maint_status_le_maint:
     description: "`Generator-maint-status-le-maint` — out of maintenance, the status in maintenance is zero"
     dims: [scenario, snapshot, generator]
-    where: Generator_maintainable AND Generator_committable AND NOT Generator_p_nom_extendable AND NOT (Generator_p_nom_mod > 0) AND Generator_active
+    where: Generator_maintainable AND Generator_committed AND NOT Generator_p_nom_extendable AND NOT (Generator_p_nom_mod > 0)
     expression: Generator_maintenance_status <= Generator_maintenance
   Generator_maint_status_lb:
     description: "`Generator-maint-status-lb` — on and in maintenance, the status in maintenance is one"
     dims: [scenario, snapshot, generator]
-    where: Generator_maintainable AND Generator_committable AND NOT Generator_p_nom_extendable AND NOT (Generator_p_nom_mod > 0) AND Generator_active
+    where: Generator_maintainable AND Generator_committed AND NOT Generator_p_nom_extendable AND NOT (Generator_p_nom_mod > 0)
     expression: Generator_maintenance_status >= Generator_status + Generator_maintenance - 1
   Generator_maint_modstatus_le_status:
     description: "`Generator-maint-modstatus-le-status` — the modules on in maintenance are at most the modules on"
     dims: [scenario, snapshot, generator]
-    where: Generator_maintainable AND Generator_committable AND Generator_p_nom_mod > 0 AND Generator_active
+    where: Generator_maintainable AND Generator_committed AND Generator_p_nom_mod > 0
     expression: Generator_maintenance_status <= Generator_status
   Generator_maint_modstatus_le_maint:
     description: >-
       `Generator-maint-modstatus-le-maint` — out of maintenance, no module is on in
       maintenance; in it, at most the modules the build cap holds
     dims: [scenario, snapshot, generator]
-    where: Generator_maintainable AND Generator_committable AND Generator_p_nom_mod > 0 AND Generator_active
+    where: Generator_maintainable AND Generator_committed AND Generator_p_nom_mod > 0
     expression: Generator_maintenance_status <= Generator_p_nom_max / Generator_p_nom_mod * Generator_maintenance
   Generator_maint_modstatus_lb:
     description: "`Generator-maint-modstatus-lb` — in maintenance, every module on is on in maintenance"
     dims: [scenario, snapshot, generator]
-    where: Generator_maintainable AND Generator_committable AND Generator_p_nom_mod > 0 AND Generator_active
+    where: Generator_maintainable AND Generator_committed AND Generator_p_nom_mod > 0
     expression: Generator_maintenance_status >= Generator_status - Generator_p_nom_max / Generator_p_nom_mod * (1 - Generator_maintenance)
 
 assumptions:
@@ -272,6 +285,13 @@ assumptions:
 | $`\overline{\mathrm{p}}^{\mathrm{nom}}`$ | `Generator_p_nom_max` over $`\Xi \times \mathcal{G}`$, data another file declares |
 | $`u`$ | `Generator_status` over $`\Xi \times \mathcal{T} \times \mathcal{G}`$ |
 | $`P`$ | `Generator_p_nom_ext` over $`\mathcal{G}`$ |
+| $`\mathrm{on}^{\mathrm{com}}`$ | `Generator_committed` over $`\mathcal{T} \times \mathcal{G}`$, a mask another file defines |
+
+#### Masks
+
+| Symbol | Meaning |
+|---|---|
+| $`\mathrm{on}^{\mathrm{mnt,ext}}`$ | `Generator_maint_ext` over $`\mathcal{T} \times \mathcal{G}`$ — a maintainable generator with an extendable build, unless it is committable and modular, that stands in the snapshot's period — the maintenance rows against the chosen build |
 
 #### Subject to
 
@@ -296,61 +316,69 @@ assumptions:
 **`Generator_maintcap_upper`**
 
 ```math
-\mu^{\mathrm{nom}}_{\xi,t,g} \le P_{g} - \underline{\mathrm{p}}^{\mathrm{nom}}_{\xi,g} \cdot \left( 1 - \mu_{\xi,t,g} \right) \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{mnt}_{g} \wedge \mathrm{ext}_{g} \wedge \neg \left( \mathrm{com}_{g} \wedge \mathrm{p}^{\mathrm{mod}}_{g} > 0 \right) \wedge \mathrm{on}_{t,g}
+\mu^{\mathrm{nom}}_{\xi,t,g} \le P_{g} - \underline{\mathrm{p}}^{\mathrm{nom}}_{\xi,g} \cdot \left( 1 - \mu_{\xi,t,g} \right) \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{on}^{\mathrm{mnt,ext}}_{t,g}
 ```
 
 **`Generator_maintcap_upper_nommax`**
 
 ```math
-\mu^{\mathrm{nom}}_{\xi,t,g} \le \overline{\mathrm{p}}^{\mathrm{nom}}_{\xi,g} \cdot \mu_{\xi,t,g} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{mnt}_{g} \wedge \mathrm{ext}_{g} \wedge \neg \left( \mathrm{com}_{g} \wedge \mathrm{p}^{\mathrm{mod}}_{g} > 0 \right) \wedge \mathrm{on}_{t,g}
+\mu^{\mathrm{nom}}_{\xi,t,g} \le \overline{\mathrm{p}}^{\mathrm{nom}}_{\xi,g} \cdot \mu_{\xi,t,g} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{on}^{\mathrm{mnt,ext}}_{t,g}
 ```
 
 **`Generator_maintcap_lower_nommax`**
 
 ```math
-\mu^{\mathrm{nom}}_{\xi,t,g} \ge P_{g} - \overline{\mathrm{p}}^{\mathrm{nom}}_{\xi,g} \cdot \left( 1 - \mu_{\xi,t,g} \right) \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{mnt}_{g} \wedge \mathrm{ext}_{g} \wedge \neg \left( \mathrm{com}_{g} \wedge \mathrm{p}^{\mathrm{mod}}_{g} > 0 \right) \wedge \mathrm{on}_{t,g}
+\mu^{\mathrm{nom}}_{\xi,t,g} \ge P_{g} - \overline{\mathrm{p}}^{\mathrm{nom}}_{\xi,g} \cdot \left( 1 - \mu_{\xi,t,g} \right) \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{on}^{\mathrm{mnt,ext}}_{t,g}
 ```
 
 **`Generator_maintcap_lower_nommin`**
 
 ```math
-\mu^{\mathrm{nom}}_{\xi,t,g} \ge \underline{\mathrm{p}}^{\mathrm{nom}}_{\xi,g} \cdot \mu_{\xi,t,g} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{mnt}_{g} \wedge \mathrm{ext}_{g} \wedge \neg \left( \mathrm{com}_{g} \wedge \mathrm{p}^{\mathrm{mod}}_{g} > 0 \right) \wedge \mathrm{on}_{t,g} \wedge \underline{\mathrm{p}}^{\mathrm{nom}}_{\xi,g} > 0
+\mu^{\mathrm{nom}}_{\xi,t,g} \ge \underline{\mathrm{p}}^{\mathrm{nom}}_{\xi,g} \cdot \mu_{\xi,t,g} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{on}^{\mathrm{mnt,ext}}_{t,g} \wedge \underline{\mathrm{p}}^{\mathrm{nom}}_{\xi,g} > 0
 ```
 
 **`Generator_maint_status_le_status`**
 
 ```math
-\mu^{u}_{\xi,t,g} \le u_{\xi,t,g} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{mnt}_{g} \wedge \mathrm{com}_{g} \wedge \neg \mathrm{ext}_{g} \wedge \neg \left( \mathrm{p}^{\mathrm{mod}}_{g} > 0 \right) \wedge \mathrm{on}_{t,g}
+\mu^{u}_{\xi,t,g} \le u_{\xi,t,g} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{mnt}_{g} \wedge \mathrm{on}^{\mathrm{com}}_{t,g} \wedge \neg \mathrm{ext}_{g} \wedge \neg \left( \mathrm{p}^{\mathrm{mod}}_{g} > 0 \right)
 ```
 
 **`Generator_maint_status_le_maint`**
 
 ```math
-\mu^{u}_{\xi,t,g} \le \mu_{\xi,t,g} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{mnt}_{g} \wedge \mathrm{com}_{g} \wedge \neg \mathrm{ext}_{g} \wedge \neg \left( \mathrm{p}^{\mathrm{mod}}_{g} > 0 \right) \wedge \mathrm{on}_{t,g}
+\mu^{u}_{\xi,t,g} \le \mu_{\xi,t,g} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{mnt}_{g} \wedge \mathrm{on}^{\mathrm{com}}_{t,g} \wedge \neg \mathrm{ext}_{g} \wedge \neg \left( \mathrm{p}^{\mathrm{mod}}_{g} > 0 \right)
 ```
 
 **`Generator_maint_status_lb`**
 
 ```math
-\mu^{u}_{\xi,t,g} \ge u_{\xi,t,g} + \mu_{\xi,t,g} - 1 \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{mnt}_{g} \wedge \mathrm{com}_{g} \wedge \neg \mathrm{ext}_{g} \wedge \neg \left( \mathrm{p}^{\mathrm{mod}}_{g} > 0 \right) \wedge \mathrm{on}_{t,g}
+\mu^{u}_{\xi,t,g} \ge u_{\xi,t,g} + \mu_{\xi,t,g} - 1 \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{mnt}_{g} \wedge \mathrm{on}^{\mathrm{com}}_{t,g} \wedge \neg \mathrm{ext}_{g} \wedge \neg \left( \mathrm{p}^{\mathrm{mod}}_{g} > 0 \right)
 ```
 
 **`Generator_maint_modstatus_le_status`**
 
 ```math
-\mu^{u}_{\xi,t,g} \le u_{\xi,t,g} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{mnt}_{g} \wedge \mathrm{com}_{g} \wedge \mathrm{p}^{\mathrm{mod}}_{g} > 0 \wedge \mathrm{on}_{t,g}
+\mu^{u}_{\xi,t,g} \le u_{\xi,t,g} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{mnt}_{g} \wedge \mathrm{on}^{\mathrm{com}}_{t,g} \wedge \mathrm{p}^{\mathrm{mod}}_{g} > 0
 ```
 
 **`Generator_maint_modstatus_le_maint`**
 
 ```math
-\mu^{u}_{\xi,t,g} \le \frac{\overline{\mathrm{p}}^{\mathrm{nom}}_{\xi,g}}{\mathrm{p}^{\mathrm{mod}}_{g}} \cdot \mu_{\xi,t,g} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{mnt}_{g} \wedge \mathrm{com}_{g} \wedge \mathrm{p}^{\mathrm{mod}}_{g} > 0 \wedge \mathrm{on}_{t,g}
+\mu^{u}_{\xi,t,g} \le \frac{\overline{\mathrm{p}}^{\mathrm{nom}}_{\xi,g}}{\mathrm{p}^{\mathrm{mod}}_{g}} \cdot \mu_{\xi,t,g} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{mnt}_{g} \wedge \mathrm{on}^{\mathrm{com}}_{t,g} \wedge \mathrm{p}^{\mathrm{mod}}_{g} > 0
 ```
 
 **`Generator_maint_modstatus_lb`**
 
 ```math
-\mu^{u}_{\xi,t,g} \ge u_{\xi,t,g} - \frac{\overline{\mathrm{p}}^{\mathrm{nom}}_{\xi,g}}{\mathrm{p}^{\mathrm{mod}}_{g}} \cdot \left( 1 - \mu_{\xi,t,g} \right) \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{mnt}_{g} \wedge \mathrm{com}_{g} \wedge \mathrm{p}^{\mathrm{mod}}_{g} > 0 \wedge \mathrm{on}_{t,g}
+\mu^{u}_{\xi,t,g} \ge u_{\xi,t,g} - \frac{\overline{\mathrm{p}}^{\mathrm{nom}}_{\xi,g}}{\mathrm{p}^{\mathrm{mod}}_{g}} \cdot \left( 1 - \mu_{\xi,t,g} \right) \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{mnt}_{g} \wedge \mathrm{on}^{\mathrm{com}}_{t,g} \wedge \mathrm{p}^{\mathrm{mod}}_{g} > 0
+```
+
+#### Masks
+
+**`Generator_maint_ext`**
+
+```math
+\mathrm{on}^{\mathrm{mnt,ext}}_{t,g} \iff \mathrm{mnt}_{g} \wedge \mathrm{ext}_{g} \wedge \neg \left( \mathrm{com}_{g} \wedge \mathrm{p}^{\mathrm{mod}}_{g} > 0 \right) \wedge \mathrm{on}_{t,g} \qquad \forall\, t \in \mathcal{T},\ g \in \mathcal{G}
 ```
 
 #### Variable domains
@@ -370,13 +398,13 @@ assumptions:
 **`Generator_maintenance_capacity`**
 
 ```math
-\mu^{\mathrm{nom}}_{\xi,t,g} \ge 0 \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{mnt}_{g} \wedge \mathrm{ext}_{g} \wedge \neg \left( \mathrm{com}_{g} \wedge \mathrm{p}^{\mathrm{mod}}_{g} > 0 \right) \wedge \mathrm{on}_{t,g}
+\mu^{\mathrm{nom}}_{\xi,t,g} \ge 0 \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{on}^{\mathrm{mnt,ext}}_{t,g}
 ```
 
 **`Generator_maintenance_status`**
 
 ```math
-\mu^{u}_{\xi,t,g} \ge 0 \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{mnt}_{g} \wedge \mathrm{com}_{g} \wedge \neg \left( \mathrm{ext}_{g} \wedge \neg \left( \mathrm{p}^{\mathrm{mod}}_{g} > 0 \right) \right) \wedge \mathrm{on}_{t,g}
+\mu^{u}_{\xi,t,g} \ge 0 \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{mnt}_{g} \wedge \mathrm{on}^{\mathrm{com}}_{t,g} \wedge \neg \left( \mathrm{ext}_{g} \wedge \neg \left( \mathrm{p}^{\mathrm{mod}}_{g} > 0 \right) \right)
 ```
 
 #### Assumptions
diff --git a/docs/examples/pypsa/generator_ramping.md b/docs/examples/pypsa/generator_ramping.md
index 695390ee..df8d2711 100644
--- a/docs/examples/pypsa/generator_ramping.md
+++ b/docs/examples/pypsa/generator_ramping.md
@@ -67,6 +67,8 @@ given:
     Generator_previous_status: { dims: [scenario, snapshot, generator] }
     Generator_p_nom_effective: { dims: [scenario, generator] }
     Generator_p_nom_committed: { dims: [scenario, generator] }
+  masks:
+    Generator_com_ext: { dims: [snapshot, generator] }
 
 expressions:
   Generator_previous_p:
@@ -139,6 +141,16 @@ expressions:
           * (Generator_previous_status - Generator_status)
     otherwise: Generator_ramp_down_rate * Generator_p_nom_effective
 
+masks:
+  Generator_ramps_from_previous:
+    description: >-
+      a snapshot whose ramp reads a previous output — any snapshot but its
+      period's first, and the horizon's first where the generator comes in off
+      or carries an initial output
+    where: >-
+      position(snapshot, within=snapshot_period[period]) > 0 OR (position(snapshot) == 0 AND
+      (Generator_status_initial == 0 OR Generator_p_init))
+
 constraints:
   Generator_p_ramp_limit_up_run_big_m:
     description: >-
@@ -147,10 +159,9 @@ constraints:
       releases the row in the snapshot it turns on
     dims: [scenario, snapshot, generator]
     where: >-
-      Generator_committable AND Generator_p_nom_extendable AND NOT (Generator_p_nom_mod > 0)
+      Generator_com_ext
       AND (Generator_ramp_limit_up OR Generator_ramp_limit_start_up)
-      AND (position(snapshot, within=snapshot_period[period]) > 0 OR (position(snapshot) == 0 AND (Generator_status_initial == 0 OR Generator_p_init)))
-      AND Generator_active
+      AND Generator_ramps_from_previous
     expression: >-
       Generator_p - Generator_previous_p <=
       Generator_ramp_up_rate * Generator_p_nom_ext
@@ -162,10 +173,9 @@ constraints:
       the chosen build; the big M releases the row everywhere else
     dims: [scenario, snapshot, generator]
     where: >-
-      Generator_committable AND Generator_p_nom_extendable AND NOT (Generator_p_nom_mod > 0)
+      Generator_com_ext
       AND (Generator_ramp_limit_up OR Generator_ramp_limit_start_up)
-      AND (position(snapshot, within=snapshot_period[period]) > 0 OR (position(snapshot) == 0 AND (Generator_status_initial == 0 OR Generator_p_init)))
-      AND Generator_active
+      AND Generator_ramps_from_previous
     expression: >-
       Generator_p - Generator_previous_p <=
       Generator_start_up_rate * Generator_p_nom_ext
@@ -177,10 +187,9 @@ constraints:
       releases the row in the snapshot it turns off
     dims: [scenario, snapshot, generator]
     where: >-
-      Generator_committable AND Generator_p_nom_extendable AND NOT (Generator_p_nom_mod > 0)
+      Generator_com_ext
       AND (Generator_ramp_limit_down OR Generator_ramp_limit_shut_down)
-      AND (position(snapshot, within=snapshot_period[period]) > 0 OR (position(snapshot) == 0 AND (Generator_status_initial == 0 OR Generator_p_init)))
-      AND Generator_active
+      AND Generator_ramps_from_previous
     expression: >-
       Generator_previous_p - Generator_p <=
       Generator_ramp_down_rate * Generator_p_nom_ext
@@ -192,10 +201,9 @@ constraints:
       the chosen build; the big M releases the row everywhere else
     dims: [scenario, snapshot, generator]
     where: >-
-      Generator_committable AND Generator_p_nom_extendable AND NOT (Generator_p_nom_mod > 0)
+      Generator_com_ext
       AND (Generator_ramp_limit_down OR Generator_ramp_limit_shut_down)
-      AND (position(snapshot, within=snapshot_period[period]) > 0 OR (position(snapshot) == 0 AND (Generator_status_initial == 0 OR Generator_p_init)))
-      AND Generator_active
+      AND Generator_ramps_from_previous
     expression: >-
       Generator_previous_p - Generator_p <=
       Generator_shut_down_rate * Generator_p_nom_ext
@@ -212,7 +220,7 @@ constraints:
     where: >-
       (Generator_ramp_limit_up OR Generator_ramp_limit_start_up)
       AND NOT (Generator_committable AND Generator_p_nom_extendable AND NOT (Generator_p_nom_mod > 0))
-      AND (position(snapshot, within=snapshot_period[period]) > 0 OR (position(snapshot) == 0 AND (Generator_status_initial == 0 OR Generator_p_init)))
+      AND Generator_ramps_from_previous
       AND Generator_active
     expression: Generator_p - Generator_previous_p <= Generator_ramp_up_allowance
   Generator_p_ramp_limit_down:
@@ -227,7 +235,7 @@ constraints:
     where: >-
       (Generator_ramp_limit_down OR Generator_ramp_limit_shut_down)
       AND NOT (Generator_committable AND Generator_p_nom_extendable AND NOT (Generator_p_nom_mod > 0))
-      AND (position(snapshot, within=snapshot_period[period]) > 0 OR (position(snapshot) == 0 AND (Generator_status_initial == 0 OR Generator_p_init)))
+      AND Generator_ramps_from_previous
       AND Generator_active
     expression: Generator_previous_p - Generator_p <= Generator_ramp_down_allowance
 
@@ -285,6 +293,7 @@ assumptions:
 | $`\overleftarrow{u}`$ | `Generator_previous_status` over $`\Xi \times \mathcal{T} \times \mathcal{G}`$, an expression another file defines |
 | $`\widetilde{\mathrm{p}}^{\mathrm{nom}}`$ | `Generator_p_nom_effective` over $`\Xi \times \mathcal{G}`$, an expression another file defines |
 | $`\widehat{\mathrm{p}}^{\mathrm{nom}}`$ | `Generator_p_nom_committed` over $`\Xi \times \mathcal{G}`$, an expression another file defines |
+| $`\mathrm{on}^{\mathrm{com,ext}}`$ | `Generator_com_ext` over $`\mathcal{T} \times \mathcal{G}`$, a mask another file defines |
 
 #### Definitions
 
@@ -298,6 +307,12 @@ assumptions:
 | $`\Delta^{+}`$ | `Generator_ramp_up_allowance` over $`\Xi \times \mathcal{T} \times \mathcal{G}`$ — how far a generator may raise output between two snapshots — its ramp limit of the build while it stays on, plus its start-up ramp in the snapshot it turns on |
 | $`\Delta^{-}`$ | `Generator_ramp_down_allowance` over $`\Xi \times \mathcal{T} \times \mathcal{G}`$ — how far a generator may lower output between two snapshots — its ramp limit of the build while it stays on, plus its shut-down ramp in the snapshot it turns off |
 
+#### Masks
+
+| Symbol | Meaning |
+|---|---|
+| $`\mathrm{prev}`$ | `Generator_ramps_from_previous` over $`\Xi \times \mathcal{T} \times \mathcal{G}`$ — a snapshot whose ramp reads a previous output — any snapshot but its period's first, and the horizon's first where the generator comes in off or carries an initial output |
+
 $`\mathrm{pos}(t)`$ denotes where index $`t`$ sits along its dimension's own order — the order `shift` steps along, not the order labels sort in — counted from $`0`$. The index itself stays the coordinate, so $`t`$ compares against labels and $`\mathrm{pos}(t)`$ against positions.
 
 $`\mathrm{pos}_{\mathrm{relation}(t)}(t)`$ counts within the group a relation puts $`t`$ in: the subscript names the map, $`\mathcal{T}_{\mathrm{relation}(t)}`$ is the group it lands in, and that group has a first position of its own.
@@ -307,37 +322,37 @@ $`\mathrm{pos}_{\mathrm{relation}(t)}(t)`$ counts within the group a relation pu
 **`Generator_p_ramp_limit_up_run_big_m`**
 
 ```math
-p_{\xi,t,g} - \overleftarrow{p}_{\xi,t,g} \le \widetilde{\mathrm{ru}}_{\xi,t,g} \cdot P_{g} + \mathrm{M}_{\xi,g} - \mathrm{M}_{\xi,g} \cdot \overleftarrow{u}_{\xi,t,g} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{com}_{g} \wedge \mathrm{ext}_{g} \wedge \neg \left( \mathrm{p}^{\mathrm{mod}}_{g} > 0 \right) \wedge \left( \mathrm{ru}_{\xi,t,g} \text{ is defined} \vee \mathrm{ru}^{\mathrm{up}}_{\xi,g} \text{ is defined} \right) \wedge \left( \mathrm{pos}_{\mathrm{snapshot\_period}(t)}(t) > 0 \vee \mathrm{pos}(t) = 0 \wedge \left( \mathrm{u}^{0}_{\xi,g} = 0 \vee \mathrm{p}^{0}_{\xi,g} \text{ is defined} \right) \right) \wedge \mathrm{on}_{t,g}
+p_{\xi,t,g} - \overleftarrow{p}_{\xi,t,g} \le \widetilde{\mathrm{ru}}_{\xi,t,g} \cdot P_{g} + \mathrm{M}_{\xi,g} - \mathrm{M}_{\xi,g} \cdot \overleftarrow{u}_{\xi,t,g} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{on}^{\mathrm{com,ext}}_{t,g} \wedge \left( \mathrm{ru}_{\xi,t,g} \text{ is defined} \vee \mathrm{ru}^{\mathrm{up}}_{\xi,g} \text{ is defined} \right) \wedge \mathrm{prev}_{\xi,t,g}
 ```
 
 **`Generator_p_ramp_limit_up_start_big_m`**
 
 ```math
-p_{\xi,t,g} - \overleftarrow{p}_{\xi,t,g} \le \widetilde{\mathrm{ru}}^{\mathrm{up}}_{\xi,g} \cdot P_{g} + \mathrm{M}_{\xi,g} - \mathrm{M}_{\xi,g} \cdot \mathit{up}_{\xi,t,g} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{com}_{g} \wedge \mathrm{ext}_{g} \wedge \neg \left( \mathrm{p}^{\mathrm{mod}}_{g} > 0 \right) \wedge \left( \mathrm{ru}_{\xi,t,g} \text{ is defined} \vee \mathrm{ru}^{\mathrm{up}}_{\xi,g} \text{ is defined} \right) \wedge \left( \mathrm{pos}_{\mathrm{snapshot\_period}(t)}(t) > 0 \vee \mathrm{pos}(t) = 0 \wedge \left( \mathrm{u}^{0}_{\xi,g} = 0 \vee \mathrm{p}^{0}_{\xi,g} \text{ is defined} \right) \right) \wedge \mathrm{on}_{t,g}
+p_{\xi,t,g} - \overleftarrow{p}_{\xi,t,g} \le \widetilde{\mathrm{ru}}^{\mathrm{up}}_{\xi,g} \cdot P_{g} + \mathrm{M}_{\xi,g} - \mathrm{M}_{\xi,g} \cdot \mathit{up}_{\xi,t,g} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{on}^{\mathrm{com,ext}}_{t,g} \wedge \left( \mathrm{ru}_{\xi,t,g} \text{ is defined} \vee \mathrm{ru}^{\mathrm{up}}_{\xi,g} \text{ is defined} \right) \wedge \mathrm{prev}_{\xi,t,g}
 ```
 
 **`Generator_p_ramp_limit_down_run_big_m`**
 
 ```math
-\overleftarrow{p}_{\xi,t,g} - p_{\xi,t,g} \le \widetilde{\mathrm{rd}}_{\xi,t,g} \cdot P_{g} + \mathrm{M}_{\xi,g} - \mathrm{M}_{\xi,g} \cdot u_{\xi,t,g} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{com}_{g} \wedge \mathrm{ext}_{g} \wedge \neg \left( \mathrm{p}^{\mathrm{mod}}_{g} > 0 \right) \wedge \left( \mathrm{rd}_{\xi,t,g} \text{ is defined} \vee \mathrm{rd}^{\mathrm{dn}}_{\xi,g} \text{ is defined} \right) \wedge \left( \mathrm{pos}_{\mathrm{snapshot\_period}(t)}(t) > 0 \vee \mathrm{pos}(t) = 0 \wedge \left( \mathrm{u}^{0}_{\xi,g} = 0 \vee \mathrm{p}^{0}_{\xi,g} \text{ is defined} \right) \right) \wedge \mathrm{on}_{t,g}
+\overleftarrow{p}_{\xi,t,g} - p_{\xi,t,g} \le \widetilde{\mathrm{rd}}_{\xi,t,g} \cdot P_{g} + \mathrm{M}_{\xi,g} - \mathrm{M}_{\xi,g} \cdot u_{\xi,t,g} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{on}^{\mathrm{com,ext}}_{t,g} \wedge \left( \mathrm{rd}_{\xi,t,g} \text{ is defined} \vee \mathrm{rd}^{\mathrm{dn}}_{\xi,g} \text{ is defined} \right) \wedge \mathrm{prev}_{\xi,t,g}
 ```
 
 **`Generator_p_ramp_limit_down_shut_big_m`**
 
 ```math
-\overleftarrow{p}_{\xi,t,g} - p_{\xi,t,g} \le \widetilde{\mathrm{rd}}^{\mathrm{dn}}_{\xi,g} \cdot P_{g} + \mathrm{M}_{\xi,g} - \mathrm{M}_{\xi,g} \cdot \mathit{dn}_{\xi,t,g} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{com}_{g} \wedge \mathrm{ext}_{g} \wedge \neg \left( \mathrm{p}^{\mathrm{mod}}_{g} > 0 \right) \wedge \left( \mathrm{rd}_{\xi,t,g} \text{ is defined} \vee \mathrm{rd}^{\mathrm{dn}}_{\xi,g} \text{ is defined} \right) \wedge \left( \mathrm{pos}_{\mathrm{snapshot\_period}(t)}(t) > 0 \vee \mathrm{pos}(t) = 0 \wedge \left( \mathrm{u}^{0}_{\xi,g} = 0 \vee \mathrm{p}^{0}_{\xi,g} \text{ is defined} \right) \right) \wedge \mathrm{on}_{t,g}
+\overleftarrow{p}_{\xi,t,g} - p_{\xi,t,g} \le \widetilde{\mathrm{rd}}^{\mathrm{dn}}_{\xi,g} \cdot P_{g} + \mathrm{M}_{\xi,g} - \mathrm{M}_{\xi,g} \cdot \mathit{dn}_{\xi,t,g} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{on}^{\mathrm{com,ext}}_{t,g} \wedge \left( \mathrm{rd}_{\xi,t,g} \text{ is defined} \vee \mathrm{rd}^{\mathrm{dn}}_{\xi,g} \text{ is defined} \right) \wedge \mathrm{prev}_{\xi,t,g}
 ```
 
 **`Generator_p_ramp_limit_up`**
 
 ```math
-p_{\xi,t,g} - \overleftarrow{p}_{\xi,t,g} \le \Delta^{+}_{\xi,t,g} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \left( \mathrm{ru}_{\xi,t,g} \text{ is defined} \vee \mathrm{ru}^{\mathrm{up}}_{\xi,g} \text{ is defined} \right) \wedge \neg \left( \mathrm{com}_{g} \wedge \mathrm{ext}_{g} \wedge \neg \left( \mathrm{p}^{\mathrm{mod}}_{g} > 0 \right) \right) \wedge \left( \mathrm{pos}_{\mathrm{snapshot\_period}(t)}(t) > 0 \vee \mathrm{pos}(t) = 0 \wedge \left( \mathrm{u}^{0}_{\xi,g} = 0 \vee \mathrm{p}^{0}_{\xi,g} \text{ is defined} \right) \right) \wedge \mathrm{on}_{t,g}
+p_{\xi,t,g} - \overleftarrow{p}_{\xi,t,g} \le \Delta^{+}_{\xi,t,g} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \left( \mathrm{ru}_{\xi,t,g} \text{ is defined} \vee \mathrm{ru}^{\mathrm{up}}_{\xi,g} \text{ is defined} \right) \wedge \neg \left( \mathrm{com}_{g} \wedge \mathrm{ext}_{g} \wedge \neg \left( \mathrm{p}^{\mathrm{mod}}_{g} > 0 \right) \right) \wedge \mathrm{prev}_{\xi,t,g} \wedge \mathrm{on}_{t,g}
 ```
 
 **`Generator_p_ramp_limit_down`**
 
 ```math
-\overleftarrow{p}_{\xi,t,g} - p_{\xi,t,g} \le \Delta^{-}_{\xi,t,g} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \left( \mathrm{rd}_{\xi,t,g} \text{ is defined} \vee \mathrm{rd}^{\mathrm{dn}}_{\xi,g} \text{ is defined} \right) \wedge \neg \left( \mathrm{com}_{g} \wedge \mathrm{ext}_{g} \wedge \neg \left( \mathrm{p}^{\mathrm{mod}}_{g} > 0 \right) \right) \wedge \left( \mathrm{pos}_{\mathrm{snapshot\_period}(t)}(t) > 0 \vee \mathrm{pos}(t) = 0 \wedge \left( \mathrm{u}^{0}_{\xi,g} = 0 \vee \mathrm{p}^{0}_{\xi,g} \text{ is defined} \right) \right) \wedge \mathrm{on}_{t,g}
+\overleftarrow{p}_{\xi,t,g} - p_{\xi,t,g} \le \Delta^{-}_{\xi,t,g} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \left( \mathrm{rd}_{\xi,t,g} \text{ is defined} \vee \mathrm{rd}^{\mathrm{dn}}_{\xi,g} \text{ is defined} \right) \wedge \neg \left( \mathrm{com}_{g} \wedge \mathrm{ext}_{g} \wedge \neg \left( \mathrm{p}^{\mathrm{mod}}_{g} > 0 \right) \right) \wedge \mathrm{prev}_{\xi,t,g} \wedge \mathrm{on}_{t,g}
 ```
 
 #### Definitions
@@ -384,6 +399,14 @@ p_{\xi,t,g} - \overleftarrow{p}_{\xi,t,g} \le \Delta^{+}_{\xi,t,g} \qquad \foral
 \Delta^{-}_{\xi,t,g} = \begin{cases} \widetilde{\mathrm{rd}}_{\xi,t,g} \cdot \widehat{\mathrm{p}}^{\mathrm{nom}}_{\xi,g} \cdot u_{\xi,t,g} + \widetilde{\mathrm{rd}}^{\mathrm{dn}}_{\xi,g} \cdot \widehat{\mathrm{p}}^{\mathrm{nom}}_{\xi,g} \cdot \left( \overleftarrow{u}_{\xi,t,g} - u_{\xi,t,g} \right) & \text{if } \mathrm{com}_{g} \\ \widetilde{\mathrm{rd}}_{\xi,t,g} \cdot \widetilde{\mathrm{p}}^{\mathrm{nom}}_{\xi,g} & \text{otherwise} \end{cases} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G}
 ```
 
+#### Masks
+
+**`Generator_ramps_from_previous`**
+
+```math
+\mathrm{prev}_{\xi,t,g} \iff \mathrm{pos}_{\mathrm{snapshot\_period}(t)}(t) > 0 \vee \mathrm{pos}(t) = 0 \wedge \left( \mathrm{u}^{0}_{\xi,g} = 0 \vee \mathrm{p}^{0}_{\xi,g} \text{ is defined} \right) \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G}
+```
+
 #### Assumptions
 
 **`Generator_came_in_running_unless_committable`**
diff --git a/docs/examples/pypsa/line.md b/docs/examples/pypsa/line.md
index 345ff802..da780d87 100644
--- a/docs/examples/pypsa/line.md
+++ b/docs/examples/pypsa/line.md
@@ -175,7 +175,7 @@ variables:
       cost and held up by the cuts; absent, and zero in the balance, where
       the network is lossless
     dims: [scenario, snapshot, line]
-    where: transmission_losses AND Line_active
+    where: Line_lossy
     absence: zero
     bounds:
       lower: 0
@@ -243,6 +243,13 @@ expressions:
     expression: sum(Line_s * at(Line_cycle_weight, by=snapshot_period[period]), over=line)
     adds_to: Cycle_angle_sum
 
+masks:
+  Line_lossy:
+    description: >-
+      a line that stands in the snapshot's period, where the run models
+      transmission losses
+    where: transmission_losses AND Line_active
+
 constraints:
   Line_fix_s_lower:
     description: "`Line-fix-s-lower` — a fixed line carries at least the negative of its rating, the loss counted against it"
@@ -307,7 +314,7 @@ constraints:
   Line_loss_upper:
     description: "`Line-loss_upper` — a line dissipates at most the loss at its rating"
     dims: [scenario, snapshot, line]
-    where: transmission_losses AND Line_active
+    where: Line_lossy
     expression: Line_loss <= Line_loss_max
   Line_loss_tangents_forward:
     description: >-
@@ -316,14 +323,14 @@ constraints:
       `k`, or one row stacked over its `secant` axis, and this block states them
       all over the segment dimension
     dims: [scenario, snapshot, line, segment]
-    where: transmission_losses AND Line_active
+    where: Line_lossy
     expression: Line_loss + Line_loss_slope * Line_s >= Line_loss_offset
   Line_loss_tangents_reverse:
     description: >-
       `Line-loss_tangents-{k}--1`, `Line-loss_secants-neg` — the same fan
       mirrored, the loss depending on the flow's magnitude
     dims: [scenario, snapshot, line, segment]
-    where: transmission_losses AND Line_active
+    where: Line_lossy
     expression: Line_loss - Line_loss_slope * Line_s >= Line_loss_offset
 ```
 
@@ -403,6 +410,12 @@ constraints:
 | $`\mathit{Line\_injection}`$ | `Line_injection` over $`\Xi \times \mathcal{T} \times \mathcal{N}`$ |
 | $`\mathit{Line\_angle\_sum}`$ | `Line_angle_sum` over $`\Xi \times \mathcal{T} \times \mathcal{C}`$ |
 
+#### Masks
+
+| Symbol | Meaning |
+|---|---|
+| $`\mathrm{on}^{s,\mathrm{lossy}}`$ | `Line_lossy` over $`\mathcal{T} \times \mathcal{K}`$ — a line that stands in the snapshot's period, where the run models transmission losses |
+
 #### Subject to
 
 **`Line_fix_s_lower`**
@@ -474,19 +487,19 @@ s_{\xi,t,k} \le \frac{\overline{\delta}_{\xi,k} \cdot \frac{3.141592653589793}{1
 **`Line_loss_upper`**
 
 ```math
-\ell_{\xi,t,k} \le \overline{\ell}_{\xi,t,k} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ k \in \mathcal{K} \,:\, \mathrm{lossy} \wedge \mathrm{on}^{s}_{t,k}
+\ell_{\xi,t,k} \le \overline{\ell}_{\xi,t,k} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ k \in \mathcal{K} \,:\, \mathrm{on}^{s,\mathrm{lossy}}_{t,k}
 ```
 
 **`Line_loss_tangents_forward`**
 
 ```math
-\ell_{\xi,t,k} + \mathrm{a}_{\xi,t,k,e} \cdot s_{\xi,t,k} \ge \mathrm{b}_{\xi,t,k,e} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ k \in \mathcal{K},\ e \in \mathcal{E} \,:\, \mathrm{lossy} \wedge \mathrm{on}^{s}_{t,k}
+\ell_{\xi,t,k} + \mathrm{a}_{\xi,t,k,e} \cdot s_{\xi,t,k} \ge \mathrm{b}_{\xi,t,k,e} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ k \in \mathcal{K},\ e \in \mathcal{E} \,:\, \mathrm{on}^{s,\mathrm{lossy}}_{t,k}
 ```
 
 **`Line_loss_tangents_reverse`**
 
 ```math
-\ell_{\xi,t,k} - \mathrm{a}_{\xi,t,k,e} \cdot s_{\xi,t,k} \ge \mathrm{b}_{\xi,t,k,e} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ k \in \mathcal{K},\ e \in \mathcal{E} \,:\, \mathrm{lossy} \wedge \mathrm{on}^{s}_{t,k}
+\ell_{\xi,t,k} - \mathrm{a}_{\xi,t,k,e} \cdot s_{\xi,t,k} \ge \mathrm{b}_{\xi,t,k,e} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ k \in \mathcal{K},\ e \in \mathcal{E} \,:\, \mathrm{on}^{s,\mathrm{lossy}}_{t,k}
 ```
 
 #### Definitions
@@ -539,6 +552,14 @@ s_{\xi,t,k} \le \frac{\overline{\delta}_{\xi,k} \cdot \frac{3.141592653589793}{1
 \mathit{Line\_angle\_sum}_{\xi,t,c} = \sum_{k \in \mathcal{K}} s_{\xi,t,k} \cdot \mathrm{x}_{\mathrm{snapshot\_period}(t),k,c} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ c \in \mathcal{C}
 ```
 
+#### Masks
+
+**`Line_lossy`**
+
+```math
+\mathrm{on}^{s,\mathrm{lossy}}_{t,k} \iff \mathrm{lossy} \wedge \mathrm{on}^{s}_{t,k} \qquad \forall\, t \in \mathcal{T},\ k \in \mathcal{K}
+```
+
 #### Variable domains
 
 **`Line_s`**
@@ -550,7 +571,7 @@ s_{\xi,t,k} \in \mathbb{R} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ k
 **`Line_loss`**
 
 ```math
-\ell_{\xi,t,k} \ge 0 \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ k \in \mathcal{K} \,:\, \mathrm{lossy} \wedge \mathrm{on}^{s}_{t,k}
+\ell_{\xi,t,k} \ge 0 \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ k \in \mathcal{K} \,:\, \mathrm{on}^{s,\mathrm{lossy}}_{t,k}
 ```
 
 **`Line_s_nom_ext`**
diff --git a/docs/examples/pypsa/link.md b/docs/examples/pypsa/link.md
index c41449a5..a43c4eea 100644
--- a/docs/examples/pypsa/link.md
+++ b/docs/examples/pypsa/link.md
@@ -274,6 +274,13 @@ expressions:
       + sum(Link_output_arrival, over=link_output, by=Link_output_bus[bus])
     adds_to: Bus_injection
 
+masks:
+  Link_committed:
+    description: >-
+      a committable link that stands in the snapshot's period — every
+      unit-commitment row's set
+    where: Link_committable AND Link_active
+
 constraints:
   Link_fix_p_lower:
     description: "`Link-fix-p-lower` — a fixed link carries at least its minimum, negative for the other way"
@@ -416,6 +423,12 @@ assumptions:
 | $`\mathit{Link\_additions}`$ | `Link_additions` over $`\mathcal{Y} \times \mathcal{I}`$ |
 | $`\mathit{Link\_injection}`$ | `Link_injection` over $`\Xi \times \mathcal{T} \times \mathcal{N}`$ |
 
+#### Masks
+
+| Symbol | Meaning |
+|---|---|
+| $`\mathrm{on}^{f,\mathrm{com}}`$ | `Link_committed` over $`\mathcal{T} \times \mathcal{L}`$ — a committable link that stands in the snapshot's period — every unit-commitment row's set |
+
 $`t \ominus k`$ denotes cyclic translation: index $`t-k`$ taken modulo the size of the dimension (`roll`). Plain $`t-k`$ (`shift`) has no wraparound — terms translated past the edge are simply absent.
 
 $`t \boxminus_{v} k`$ denotes translation with $`v`$ standing where index $`t-k`$ leaves the dimension (`shift(edge=v)`), so the row at that boundary is built and carries $`v`$ rather than being dropped.
@@ -540,6 +553,14 @@ f_{\xi,t,l} = \mathrm{f}^{\mathrm{set}}_{\xi,t,l} \qquad \forall\, \xi \in \Xi,\
 \mathit{Link\_injection}_{\xi,t,n} = -\left( \sum_{l \in \mathcal{L} \,:\, \mathrm{Link\_bus0}(l) = n} f_{\xi,t,l} \right) + \sum_{o \in \mathcal{O} \,:\, \mathrm{Link\_output\_bus}(o) = n} \overrightarrow{f}_{\xi,t,o} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ n \in \mathcal{N}
 ```
 
+#### Masks
+
+**`Link_committed`**
+
+```math
+\mathrm{on}^{f,\mathrm{com}}_{t,l} \iff \mathrm{com}^{f}_{l} \wedge \mathrm{on}^{f}_{t,l} \qquad \forall\, t \in \mathcal{T},\ l \in \mathcal{L}
+```
+
 #### Variable domains
 
 **`Link_p`**
diff --git a/docs/examples/pypsa/link_commitment.md b/docs/examples/pypsa/link_commitment.md
index 9884826e..321b2d9f 100644
--- a/docs/examples/pypsa/link_commitment.md
+++ b/docs/examples/pypsa/link_commitment.md
@@ -88,21 +88,21 @@ variables:
       the rows below cap at one, or at the module count where the build is
       modular
     dims: [scenario, snapshot, link]
-    where: Link_committable AND Link_active
+    where: Link_committed
     domain: integer
     bounds:
       lower: 0
   Link_start_up:
     description: "`Link-start_up` — how much of a committable link turns on this snapshot, capped as the status is"
     dims: [scenario, snapshot, link]
-    where: Link_committable AND Link_active
+    where: Link_committed
     domain: integer
     bounds:
       lower: 0
   Link_shut_down:
     description: "`Link-shut_down` — how much of a committable link turns off this snapshot, capped as the status is"
     dims: [scenario, snapshot, link]
-    where: Link_committable AND Link_active
+    where: Link_committed
     domain: integer
     bounds:
       lower: 0
@@ -128,6 +128,8 @@ given:
     Link_p_nom_ext: { dims: [link] }
   expressions:
     scenario_opex: { dims: [scenario] }
+  masks:
+    Link_committed: { dims: [snapshot, link] }
 
 expressions:
   Link_previous_status:
@@ -155,26 +157,38 @@ expressions:
       + sum(sum(Link_shut_down * Link_shut_down_cost, over=link), over=snapshot)
     adds_to: scenario_opex
 
+masks:
+  Link_com_ext:
+    description: >-
+      a committable link with an extendable, non-modular build that stands in
+      the snapshot's period — PyPSA's `com-ext` rows, whose status is relaxed
+      against the chosen build
+    where: >-
+      Link_committable
+      AND Link_p_nom_extendable
+      AND NOT (Link_p_nom_mod > 0)
+      AND Link_active
+
 constraints:
   Link_com_p_lower:
     description: "`Link-com-p-lower` — a committed link flows at least its minimum; off, at least nothing"
     dims: [scenario, snapshot, link]
-    where: Link_committable AND not Link_p_nom_extendable AND NOT (Link_p_nom_mod > 0) AND Link_active
+    where: Link_committed AND NOT Link_p_nom_extendable AND NOT (Link_p_nom_mod > 0)
     expression: Link_p >= Link_p_min_pu * Link_p_nom * (Link_status - Link_maintenance_pu * Link_maintenance_status)
   Link_com_p_upper:
     description: "`Link-com-p-upper` — a committed link flows at most what is available; off, at most nothing"
     dims: [scenario, snapshot, link]
-    where: Link_committable AND not Link_p_nom_extendable AND NOT (Link_p_nom_mod > 0) AND Link_active
+    where: Link_committed AND NOT Link_p_nom_extendable AND NOT (Link_p_nom_mod > 0)
     expression: Link_p <= Link_p_max_pu * Link_p_nom * (Link_status - Link_maintenance_pu * Link_maintenance_status)
   Link_com_transition_start_up:
     description: "`Link-com-transition-start-up` — turning on is a start, counted against the state the link carried into the snapshot"
     dims: [scenario, snapshot, link]
-    where: Link_committable AND Link_active
+    where: Link_committed
     expression: Link_start_up >= Link_status - Link_previous_status
   Link_com_transition_shut_down:
     description: "`Link-com-transition-shut-down` — turning off is a stop, counted against the state the link carried into the snapshot"
     dims: [scenario, snapshot, link]
-    where: Link_committable AND Link_active
+    where: Link_committed
     expression: Link_shut_down >= Link_previous_status - Link_status
   Link_com_up_time:
     description: >-
@@ -182,7 +196,7 @@ constraints:
       is still on. The first snapshot's share of the window is the brought-in
       up time's, which the must-stay-up mask carries
     dims: [scenario, snapshot, link]
-    where: Link_committable AND Link_min_up_time > 0 AND position(snapshot) > 0 AND Link_active
+    where: Link_committed AND Link_min_up_time > 0 AND position(snapshot) > 0
     expression: sum_back(Link_start_up, along=snapshot, window=Link_min_up_time) <= Link_status
   Link_com_down_time:
     description: >-
@@ -190,38 +204,38 @@ constraints:
       time is still off. The first snapshot's share of the window is the
       brought-in down time's, which the must-stay-down mask carries
     dims: [scenario, snapshot, link]
-    where: Link_committable AND Link_min_down_time > 0 AND position(snapshot) > 0 AND Link_active
+    where: Link_committed AND Link_min_down_time > 0 AND position(snapshot) > 0
     expression: sum_back(Link_shut_down, along=snapshot, window=Link_min_down_time) <= 1 - Link_status
   Link_com_status_must_stay_up:
     description: "`Link-com-status-min_up_time_must_stay_up` — a link still serving the up time it brought in stays on"
     dims: [scenario, snapshot, link]
-    where: Link_committable AND Link_must_stay_up AND Link_active
+    where: Link_committed AND Link_must_stay_up
     expression: Link_status == 1
   Link_com_status_must_stay_down:
     description: >-
       `Link-com-status-min_down_time_must_stay_up` — a link still serving
       the down time it brought in stays off; PyPSA names the row `_must_stay_up`
     dims: [scenario, snapshot, link]
-    where: Link_committable AND Link_must_stay_down AND Link_active
+    where: Link_committed AND Link_must_stay_down
     expression: Link_status == 0
   Link_com_ext_p_upper_cap:
     description: >-
       `Link-com-ext-p-upper-cap` — a committed extendable link flows
       at most what is available of the chosen build, whatever its status
     dims: [scenario, snapshot, link]
-    where: Link_committable AND Link_p_nom_extendable AND NOT (Link_p_nom_mod > 0) AND Link_active
+    where: Link_com_ext
     expression: Link_p <= Link_p_max_pu * (Link_p_nom_ext - Link_maintenance_pu * Link_maintenance_capacity)
   Link_com_ext_p_upper_big_m:
     description: "`Link-com-ext-p-upper-bigM` — off, a link flows nothing; on, the big M is no bound"
     dims: [scenario, snapshot, link]
-    where: Link_committable AND Link_p_nom_extendable AND NOT (Link_p_nom_mod > 0) AND Link_active
+    where: Link_com_ext
     expression: Link_p <= Link_big_m * Link_status
   Link_com_ext_p_lower:
     description: >-
       `Link-com-ext-p-lower` — a committed extendable link flows at
       least its minimum of the chosen build; off, the big M releases the row
     dims: [scenario, snapshot, link]
-    where: Link_committable AND Link_p_nom_extendable AND NOT (Link_p_nom_mod > 0) AND Link_active
+    where: Link_com_ext
     expression: >-
       Link_p >=
       Link_p_min_pu * (Link_p_nom_ext - Link_maintenance_pu * Link_maintenance_capacity)
@@ -232,23 +246,21 @@ constraints:
       negative, flow is also plainly non-negative, a row the big-M lower
       cannot assert while the link is off
     dims: [scenario, snapshot, link]
-    where: >-
-      Link_committable AND Link_p_nom_extendable
-      AND Link_p_min_pu_nonneg AND NOT (Link_p_nom_mod > 0) AND Link_active
+    where: Link_com_ext AND Link_p_min_pu_nonneg
     expression: Link_p >= 0
   Link_com_mod_p_lower:
     description: >-
       `Link-com-mod-p-lower` — a committed modular link flows at least
       its minimum of one module, whether the build is fixed or a decision
     dims: [scenario, snapshot, link]
-    where: Link_committable AND Link_p_nom_mod > 0 AND Link_active
+    where: Link_committed AND Link_p_nom_mod > 0
     expression: Link_p >= Link_p_min_pu * Link_p_nom_mod * (Link_status - Link_maintenance_pu * Link_maintenance_status)
   Link_com_mod_p_upper:
     description: >-
       `Link-com-mod-p-upper` — a committed modular link flows at most
       one module's share, whether the build is fixed or a decision
     dims: [scenario, snapshot, link]
-    where: Link_committable AND Link_p_nom_mod > 0 AND Link_active
+    where: Link_committed AND Link_p_nom_mod > 0
     expression: Link_p <= Link_p_max_pu * Link_p_nom_mod * (Link_status - Link_maintenance_pu * Link_maintenance_status)
   Link_status_p_fixed_upper:
     description: >-
@@ -256,7 +268,7 @@ constraints:
       place, an explicit row as PyPSA writes it: one where the build is not
       modular, and the fixed build's whole count of modules where it is
     dims: [scenario, snapshot, link]
-    where: Link_committable AND NOT (Link_p_nom_extendable AND Link_p_nom_mod > 0) AND Link_active
+    where: Link_committed AND NOT (Link_p_nom_extendable AND Link_p_nom_mod > 0)
     expression: Link_status <= Link_modules_installed
   Link_start_up_p_fixed_upper:
     description: >-
@@ -264,7 +276,7 @@ constraints:
       place, an explicit row as PyPSA writes it: one where the build is not
       modular, and the fixed build's whole count of modules where it is
     dims: [scenario, snapshot, link]
-    where: Link_committable AND NOT (Link_p_nom_extendable AND Link_p_nom_mod > 0) AND Link_active
+    where: Link_committed AND NOT (Link_p_nom_extendable AND Link_p_nom_mod > 0)
     expression: Link_start_up <= Link_modules_installed
   Link_shut_down_p_fixed_upper:
     description: >-
@@ -272,22 +284,22 @@ constraints:
       place, an explicit row as PyPSA writes it: one where the build is not
       modular, and the fixed build's whole count of modules where it is
     dims: [scenario, snapshot, link]
-    where: Link_committable AND NOT (Link_p_nom_extendable AND Link_p_nom_mod > 0) AND Link_active
+    where: Link_committed AND NOT (Link_p_nom_extendable AND Link_p_nom_mod > 0)
     expression: Link_shut_down <= Link_modules_installed
   Link_status_p_nom_variable_upper:
     description: "`Link-status-p_nom-variable-upper` — a modular link is on only where a module is built"
     dims: [scenario, snapshot, link]
-    where: Link_committable AND Link_p_nom_extendable AND Link_p_nom_mod > 0 AND Link_active
+    where: Link_committed AND Link_p_nom_extendable AND Link_p_nom_mod > 0
     expression: Link_status <= Link_n_mod
   Link_start_up_p_nom_variable_upper:
     description: "`Link-start_up-p_nom-variable-upper` — a modular link starts only where a module is built"
     dims: [scenario, snapshot, link]
-    where: Link_committable AND Link_p_nom_extendable AND Link_p_nom_mod > 0 AND Link_active
+    where: Link_committed AND Link_p_nom_extendable AND Link_p_nom_mod > 0
     expression: Link_start_up <= Link_n_mod
   Link_shut_down_p_nom_variable_upper:
     description: "`Link-shut_down-p_nom-variable-upper` — a modular link stops only where a module is built"
     dims: [scenario, snapshot, link]
-    where: Link_committable AND Link_p_nom_extendable AND Link_p_nom_mod > 0 AND Link_active
+    where: Link_committed AND Link_p_nom_extendable AND Link_p_nom_mod > 0
     expression: Link_shut_down <= Link_n_mod
 ```
 
@@ -344,6 +356,7 @@ constraints:
 | $`\mu^{f,u}`$ | `Link_maintenance_status` over $`\Xi \times \mathcal{T} \times \mathcal{L}`$ |
 | $`F`$ | `Link_p_nom_ext` over $`\mathcal{L}`$ |
 | $`\mathit{scenario\_opex}`$ | `scenario_opex` over $`\Xi`$, an expression this file adds `Link_commitment_opex` to |
+| $`\mathrm{on}^{f,\mathrm{com}}`$ | `Link_committed` over $`\mathcal{T} \times \mathcal{L}`$, a mask another file defines |
 
 #### Definitions
 
@@ -353,6 +366,12 @@ constraints:
 | $`\overleftarrow{u}^{\circ f}`$ | `Link_status_carried_over` over $`\Xi \times \mathcal{T} \times \mathcal{L}`$ — the state a link carries over into a snapshot — the state it brought into the horizon at the first, the previous snapshot's after that |
 | $`\mathit{Link\_commitment\_opex}`$ | `Link_commitment_opex` over $`\Xi`$ |
 
+#### Masks
+
+| Symbol | Meaning |
+|---|---|
+| $`\mathrm{on}^{f,\mathrm{com,ext}}`$ | `Link_com_ext` over $`\mathcal{T} \times \mathcal{L}`$ — a committable link with an extendable, non-modular build that stands in the snapshot's period — PyPSA's `com-ext` rows, whose status is relaxed against the chosen build |
+
 $`\mathrm{pos}(t)`$ denotes where index $`t`$ sits along its dimension's own order — the order `shift` steps along, not the order labels sort in — counted from $`0`$. The index itself stays the coordinate, so $`t`$ compares against labels and $`\mathrm{pos}(t)`$ against positions.
 
 #### Subject to
@@ -360,121 +379,121 @@ $`\mathrm{pos}(t)`$ denotes where index $`t`$ sits along its dimension's own ord
 **`Link_com_p_lower`**
 
 ```math
-f_{\xi,t,l} \ge \underline{\mathrm{f}}_{\xi,t,l} \cdot \mathrm{f}^{\mathrm{nom}}_{\xi,l} \cdot \left( u^{f}_{\xi,t,l} - \gamma^{f}_{\xi,l} \cdot \mu^{f,u}_{\xi,t,l} \right) \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{com}^{f}_{l} \wedge \neg \mathrm{ext}^{f}_{l} \wedge \neg \left( \mathrm{f}^{\mathrm{mod}}_{l} > 0 \right) \wedge \mathrm{on}^{f}_{t,l}
+f_{\xi,t,l} \ge \underline{\mathrm{f}}_{\xi,t,l} \cdot \mathrm{f}^{\mathrm{nom}}_{\xi,l} \cdot \left( u^{f}_{\xi,t,l} - \gamma^{f}_{\xi,l} \cdot \mu^{f,u}_{\xi,t,l} \right) \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{on}^{f,\mathrm{com}}_{t,l} \wedge \neg \mathrm{ext}^{f}_{l} \wedge \neg \left( \mathrm{f}^{\mathrm{mod}}_{l} > 0 \right)
 ```
 
 **`Link_com_p_upper`**
 
 ```math
-f_{\xi,t,l} \le \overline{\mathrm{f}}_{\xi,t,l} \cdot \mathrm{f}^{\mathrm{nom}}_{\xi,l} \cdot \left( u^{f}_{\xi,t,l} - \gamma^{f}_{\xi,l} \cdot \mu^{f,u}_{\xi,t,l} \right) \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{com}^{f}_{l} \wedge \neg \mathrm{ext}^{f}_{l} \wedge \neg \left( \mathrm{f}^{\mathrm{mod}}_{l} > 0 \right) \wedge \mathrm{on}^{f}_{t,l}
+f_{\xi,t,l} \le \overline{\mathrm{f}}_{\xi,t,l} \cdot \mathrm{f}^{\mathrm{nom}}_{\xi,l} \cdot \left( u^{f}_{\xi,t,l} - \gamma^{f}_{\xi,l} \cdot \mu^{f,u}_{\xi,t,l} \right) \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{on}^{f,\mathrm{com}}_{t,l} \wedge \neg \mathrm{ext}^{f}_{l} \wedge \neg \left( \mathrm{f}^{\mathrm{mod}}_{l} > 0 \right)
 ```
 
 **`Link_com_transition_start_up`**
 
 ```math
-\mathit{up}^{f}_{\xi,t,l} \ge u^{f}_{\xi,t,l} - \overleftarrow{u}^{f}_{\xi,t,l} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{com}^{f}_{l} \wedge \mathrm{on}^{f}_{t,l}
+\mathit{up}^{f}_{\xi,t,l} \ge u^{f}_{\xi,t,l} - \overleftarrow{u}^{f}_{\xi,t,l} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{on}^{f,\mathrm{com}}_{t,l}
 ```
 
 **`Link_com_transition_shut_down`**
 
 ```math
-\mathit{dn}^{f}_{\xi,t,l} \ge \overleftarrow{u}^{f}_{\xi,t,l} - u^{f}_{\xi,t,l} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{com}^{f}_{l} \wedge \mathrm{on}^{f}_{t,l}
+\mathit{dn}^{f}_{\xi,t,l} \ge \overleftarrow{u}^{f}_{\xi,t,l} - u^{f}_{\xi,t,l} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{on}^{f,\mathrm{com}}_{t,l}
 ```
 
 **`Link_com_up_time`**
 
 ```math
-\sum_{t' \in \mathcal{T} \,:\, 0 \le t - t' < \mathrm{UT}^{f}} \mathit{up}^{f}_{\xi,t',l} \le u^{f}_{\xi,t,l} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{com}^{f}_{l} \wedge \mathrm{UT}^{f}_{\xi,l} > 0 \wedge \mathrm{pos}(t) > 0 \wedge \mathrm{on}^{f}_{t,l}
+\sum_{t' \in \mathcal{T} \,:\, 0 \le t - t' < \mathrm{UT}^{f}} \mathit{up}^{f}_{\xi,t',l} \le u^{f}_{\xi,t,l} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{on}^{f,\mathrm{com}}_{t,l} \wedge \mathrm{UT}^{f}_{\xi,l} > 0 \wedge \mathrm{pos}(t) > 0
 ```
 
 **`Link_com_down_time`**
 
 ```math
-\sum_{t' \in \mathcal{T} \,:\, 0 \le t - t' < \mathrm{DT}^{f}} \mathit{dn}^{f}_{\xi,t',l} \le 1 - u^{f}_{\xi,t,l} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{com}^{f}_{l} \wedge \mathrm{DT}^{f}_{\xi,l} > 0 \wedge \mathrm{pos}(t) > 0 \wedge \mathrm{on}^{f}_{t,l}
+\sum_{t' \in \mathcal{T} \,:\, 0 \le t - t' < \mathrm{DT}^{f}} \mathit{dn}^{f}_{\xi,t',l} \le 1 - u^{f}_{\xi,t,l} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{on}^{f,\mathrm{com}}_{t,l} \wedge \mathrm{DT}^{f}_{\xi,l} > 0 \wedge \mathrm{pos}(t) > 0
 ```
 
 **`Link_com_status_must_stay_up`**
 
 ```math
-u^{f}_{\xi,t,l} = 1 \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{com}^{f}_{l} \wedge \mathrm{hold}^{f}_{\xi,t,l} \wedge \mathrm{on}^{f}_{t,l}
+u^{f}_{\xi,t,l} = 1 \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{on}^{f,\mathrm{com}}_{t,l} \wedge \mathrm{hold}^{f}_{\xi,t,l}
 ```
 
 **`Link_com_status_must_stay_down`**
 
 ```math
-u^{f}_{\xi,t,l} = 0 \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{com}^{f}_{l} \wedge \mathrm{rest}^{f}_{\xi,t,l} \wedge \mathrm{on}^{f}_{t,l}
+u^{f}_{\xi,t,l} = 0 \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{on}^{f,\mathrm{com}}_{t,l} \wedge \mathrm{rest}^{f}_{\xi,t,l}
 ```
 
 **`Link_com_ext_p_upper_cap`**
 
 ```math
-f_{\xi,t,l} \le \overline{\mathrm{f}}_{\xi,t,l} \cdot \left( F_{l} - \gamma^{f}_{\xi,l} \cdot \mu^{f,\mathrm{nom}}_{\xi,t,l} \right) \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{com}^{f}_{l} \wedge \mathrm{ext}^{f}_{l} \wedge \neg \left( \mathrm{f}^{\mathrm{mod}}_{l} > 0 \right) \wedge \mathrm{on}^{f}_{t,l}
+f_{\xi,t,l} \le \overline{\mathrm{f}}_{\xi,t,l} \cdot \left( F_{l} - \gamma^{f}_{\xi,l} \cdot \mu^{f,\mathrm{nom}}_{\xi,t,l} \right) \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{on}^{f,\mathrm{com,ext}}_{t,l}
 ```
 
 **`Link_com_ext_p_upper_big_m`**
 
 ```math
-f_{\xi,t,l} \le \mathrm{M}^{f}_{\xi,l} \cdot u^{f}_{\xi,t,l} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{com}^{f}_{l} \wedge \mathrm{ext}^{f}_{l} \wedge \neg \left( \mathrm{f}^{\mathrm{mod}}_{l} > 0 \right) \wedge \mathrm{on}^{f}_{t,l}
+f_{\xi,t,l} \le \mathrm{M}^{f}_{\xi,l} \cdot u^{f}_{\xi,t,l} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{on}^{f,\mathrm{com,ext}}_{t,l}
 ```
 
 **`Link_com_ext_p_lower`**
 
 ```math
-f_{\xi,t,l} \ge \underline{\mathrm{f}}_{\xi,t,l} \cdot \left( F_{l} - \gamma^{f}_{\xi,l} \cdot \mu^{f,\mathrm{nom}}_{\xi,t,l} \right) + \mathrm{M}^{f}_{\xi,l} \cdot u^{f}_{\xi,t,l} - \mathrm{M}^{f}_{\xi,l} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{com}^{f}_{l} \wedge \mathrm{ext}^{f}_{l} \wedge \neg \left( \mathrm{f}^{\mathrm{mod}}_{l} > 0 \right) \wedge \mathrm{on}^{f}_{t,l}
+f_{\xi,t,l} \ge \underline{\mathrm{f}}_{\xi,t,l} \cdot \left( F_{l} - \gamma^{f}_{\xi,l} \cdot \mu^{f,\mathrm{nom}}_{\xi,t,l} \right) + \mathrm{M}^{f}_{\xi,l} \cdot u^{f}_{\xi,t,l} - \mathrm{M}^{f}_{\xi,l} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{on}^{f,\mathrm{com,ext}}_{t,l}
 ```
 
 **`Link_com_ext_p_lower_nonneg`**
 
 ```math
-f_{\xi,t,l} \ge 0 \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{com}^{f}_{l} \wedge \mathrm{ext}^{f}_{l} \wedge \mathrm{nonneg}^{f}_{l} \wedge \neg \left( \mathrm{f}^{\mathrm{mod}}_{l} > 0 \right) \wedge \mathrm{on}^{f}_{t,l}
+f_{\xi,t,l} \ge 0 \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{on}^{f,\mathrm{com,ext}}_{t,l} \wedge \mathrm{nonneg}^{f}_{l}
 ```
 
 **`Link_com_mod_p_lower`**
 
 ```math
-f_{\xi,t,l} \ge \underline{\mathrm{f}}_{\xi,t,l} \cdot \mathrm{f}^{\mathrm{mod}}_{l} \cdot \left( u^{f}_{\xi,t,l} - \gamma^{f}_{\xi,l} \cdot \mu^{f,u}_{\xi,t,l} \right) \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{com}^{f}_{l} \wedge \mathrm{f}^{\mathrm{mod}}_{l} > 0 \wedge \mathrm{on}^{f}_{t,l}
+f_{\xi,t,l} \ge \underline{\mathrm{f}}_{\xi,t,l} \cdot \mathrm{f}^{\mathrm{mod}}_{l} \cdot \left( u^{f}_{\xi,t,l} - \gamma^{f}_{\xi,l} \cdot \mu^{f,u}_{\xi,t,l} \right) \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{on}^{f,\mathrm{com}}_{t,l} \wedge \mathrm{f}^{\mathrm{mod}}_{l} > 0
 ```
 
 **`Link_com_mod_p_upper`**
 
 ```math
-f_{\xi,t,l} \le \overline{\mathrm{f}}_{\xi,t,l} \cdot \mathrm{f}^{\mathrm{mod}}_{l} \cdot \left( u^{f}_{\xi,t,l} - \gamma^{f}_{\xi,l} \cdot \mu^{f,u}_{\xi,t,l} \right) \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{com}^{f}_{l} \wedge \mathrm{f}^{\mathrm{mod}}_{l} > 0 \wedge \mathrm{on}^{f}_{t,l}
+f_{\xi,t,l} \le \overline{\mathrm{f}}_{\xi,t,l} \cdot \mathrm{f}^{\mathrm{mod}}_{l} \cdot \left( u^{f}_{\xi,t,l} - \gamma^{f}_{\xi,l} \cdot \mu^{f,u}_{\xi,t,l} \right) \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{on}^{f,\mathrm{com}}_{t,l} \wedge \mathrm{f}^{\mathrm{mod}}_{l} > 0
 ```
 
 **`Link_status_p_fixed_upper`**
 
 ```math
-u^{f}_{\xi,t,l} \le \mathrm{N}^{f,\mathrm{fix}}_{\xi,l} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{com}^{f}_{l} \wedge \neg \left( \mathrm{ext}^{f}_{l} \wedge \mathrm{f}^{\mathrm{mod}}_{l} > 0 \right) \wedge \mathrm{on}^{f}_{t,l}
+u^{f}_{\xi,t,l} \le \mathrm{N}^{f,\mathrm{fix}}_{\xi,l} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{on}^{f,\mathrm{com}}_{t,l} \wedge \neg \left( \mathrm{ext}^{f}_{l} \wedge \mathrm{f}^{\mathrm{mod}}_{l} > 0 \right)
 ```
 
 **`Link_start_up_p_fixed_upper`**
 
 ```math
-\mathit{up}^{f}_{\xi,t,l} \le \mathrm{N}^{f,\mathrm{fix}}_{\xi,l} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{com}^{f}_{l} \wedge \neg \left( \mathrm{ext}^{f}_{l} \wedge \mathrm{f}^{\mathrm{mod}}_{l} > 0 \right) \wedge \mathrm{on}^{f}_{t,l}
+\mathit{up}^{f}_{\xi,t,l} \le \mathrm{N}^{f,\mathrm{fix}}_{\xi,l} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{on}^{f,\mathrm{com}}_{t,l} \wedge \neg \left( \mathrm{ext}^{f}_{l} \wedge \mathrm{f}^{\mathrm{mod}}_{l} > 0 \right)
 ```
 
 **`Link_shut_down_p_fixed_upper`**
 
 ```math
-\mathit{dn}^{f}_{\xi,t,l} \le \mathrm{N}^{f,\mathrm{fix}}_{\xi,l} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{com}^{f}_{l} \wedge \neg \left( \mathrm{ext}^{f}_{l} \wedge \mathrm{f}^{\mathrm{mod}}_{l} > 0 \right) \wedge \mathrm{on}^{f}_{t,l}
+\mathit{dn}^{f}_{\xi,t,l} \le \mathrm{N}^{f,\mathrm{fix}}_{\xi,l} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{on}^{f,\mathrm{com}}_{t,l} \wedge \neg \left( \mathrm{ext}^{f}_{l} \wedge \mathrm{f}^{\mathrm{mod}}_{l} > 0 \right)
 ```
 
 **`Link_status_p_nom_variable_upper`**
 
 ```math
-u^{f}_{\xi,t,l} \le N^{f}_{l} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{com}^{f}_{l} \wedge \mathrm{ext}^{f}_{l} \wedge \mathrm{f}^{\mathrm{mod}}_{l} > 0 \wedge \mathrm{on}^{f}_{t,l}
+u^{f}_{\xi,t,l} \le N^{f}_{l} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{on}^{f,\mathrm{com}}_{t,l} \wedge \mathrm{ext}^{f}_{l} \wedge \mathrm{f}^{\mathrm{mod}}_{l} > 0
 ```
 
 **`Link_start_up_p_nom_variable_upper`**
 
 ```math
-\mathit{up}^{f}_{\xi,t,l} \le N^{f}_{l} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{com}^{f}_{l} \wedge \mathrm{ext}^{f}_{l} \wedge \mathrm{f}^{\mathrm{mod}}_{l} > 0 \wedge \mathrm{on}^{f}_{t,l}
+\mathit{up}^{f}_{\xi,t,l} \le N^{f}_{l} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{on}^{f,\mathrm{com}}_{t,l} \wedge \mathrm{ext}^{f}_{l} \wedge \mathrm{f}^{\mathrm{mod}}_{l} > 0
 ```
 
 **`Link_shut_down_p_nom_variable_upper`**
 
 ```math
-\mathit{dn}^{f}_{\xi,t,l} \le N^{f}_{l} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{com}^{f}_{l} \wedge \mathrm{ext}^{f}_{l} \wedge \mathrm{f}^{\mathrm{mod}}_{l} > 0 \wedge \mathrm{on}^{f}_{t,l}
+\mathit{dn}^{f}_{\xi,t,l} \le N^{f}_{l} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{on}^{f,\mathrm{com}}_{t,l} \wedge \mathrm{ext}^{f}_{l} \wedge \mathrm{f}^{\mathrm{mod}}_{l} > 0
 ```
 
 #### Definitions
@@ -497,23 +516,31 @@ u^{f}_{\xi,t,l} \le N^{f}_{l} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\
 \mathit{Link\_commitment\_opex}_{\xi} = \sum_{t \in \mathcal{T}} \sum_{l \in \mathcal{L}} u^{f}_{\xi,t,l} \cdot \mathrm{c}^{f,\mathrm{on}}_{\xi,t,l} \cdot \mathrm{w}_{t} \cdot \mathrm{w}^{y}_{\mathrm{snapshot\_period}(t)} + \sum_{t \in \mathcal{T}} \sum_{l \in \mathcal{L}} \mathit{up}^{f}_{\xi,t,l} \cdot \mathrm{c}^{f,\mathrm{up}}_{\xi,t,l} + \sum_{t \in \mathcal{T}} \sum_{l \in \mathcal{L}} \mathit{dn}^{f}_{\xi,t,l} \cdot \mathrm{c}^{f,\mathrm{dn}}_{\xi,t,l} \qquad \forall\, \xi \in \Xi
 ```
 
+#### Masks
+
+**`Link_com_ext`**
+
+```math
+\mathrm{on}^{f,\mathrm{com,ext}}_{t,l} \iff \mathrm{com}^{f}_{l} \wedge \mathrm{ext}^{f}_{l} \wedge \neg \left( \mathrm{f}^{\mathrm{mod}}_{l} > 0 \right) \wedge \mathrm{on}^{f}_{t,l} \qquad \forall\, t \in \mathcal{T},\ l \in \mathcal{L}
+```
+
 #### Variable domains
 
 **`Link_status`**
 
 ```math
-u^{f}_{\xi,t,l} \ge 0, u^{f}_{\xi,t,l} \in \mathbb{Z} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{com}^{f}_{l} \wedge \mathrm{on}^{f}_{t,l}
+u^{f}_{\xi,t,l} \ge 0, u^{f}_{\xi,t,l} \in \mathbb{Z} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{on}^{f,\mathrm{com}}_{t,l}
 ```
 
 **`Link_start_up`**
 
 ```math
-\mathit{up}^{f}_{\xi,t,l} \ge 0, \mathit{up}^{f}_{\xi,t,l} \in \mathbb{Z} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{com}^{f}_{l} \wedge \mathrm{on}^{f}_{t,l}
+\mathit{up}^{f}_{\xi,t,l} \ge 0, \mathit{up}^{f}_{\xi,t,l} \in \mathbb{Z} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{on}^{f,\mathrm{com}}_{t,l}
 ```
 
 **`Link_shut_down`**
 
 ```math
-\mathit{dn}^{f}_{\xi,t,l} \ge 0, \mathit{dn}^{f}_{\xi,t,l} \in \mathbb{Z} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{com}^{f}_{l} \wedge \mathrm{on}^{f}_{t,l}
+\mathit{dn}^{f}_{\xi,t,l} \ge 0, \mathit{dn}^{f}_{\xi,t,l} \in \mathbb{Z} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{on}^{f,\mathrm{com}}_{t,l}
 ```
 <!-- gallery:end -->
diff --git a/docs/examples/pypsa/link_maintenance.md b/docs/examples/pypsa/link_maintenance.md
index 07a28342..c057d698 100644
--- a/docs/examples/pypsa/link_maintenance.md
+++ b/docs/examples/pypsa/link_maintenance.md
@@ -82,9 +82,7 @@ variables:
       `Link-maintenance_capacity` — the chosen build while in maintenance, zero
       otherwise: the product the `maintcap` rows linearize
     dims: [scenario, snapshot, link]
-    where: >-
-      Link_maintainable AND Link_p_nom_extendable
-      AND NOT (Link_committable AND Link_p_nom_mod > 0) AND Link_active
+    where: Link_maint_ext
     absence: zero
     bounds:
       lower: 0
@@ -94,9 +92,7 @@ variables:
       otherwise: the product the `maint-status` rows linearize, so a unit in
       maintenance may also be off
     dims: [scenario, snapshot, link]
-    where: >-
-      Link_maintainable AND Link_committable
-      AND NOT (Link_p_nom_extendable AND NOT (Link_p_nom_mod > 0)) AND Link_active
+    where: Link_maintainable AND Link_committed AND NOT (Link_p_nom_extendable AND NOT (Link_p_nom_mod > 0))
     absence: zero
     bounds:
       lower: 0
@@ -113,6 +109,20 @@ given:
   variables:
     Link_status: { dims: [scenario, snapshot, link], domain: integer }
     Link_p_nom_ext: { dims: [link] }
+  masks:
+    Link_committed: { dims: [snapshot, link] }
+
+masks:
+  Link_maint_ext:
+    description: >-
+      a maintainable link with an extendable build, unless it is committable
+      and modular, that stands in the snapshot's period — the maintenance rows
+      against the chosen build
+    where: >-
+      Link_maintainable
+      AND Link_p_nom_extendable
+      AND NOT (Link_committable AND Link_p_nom_mod > 0)
+      AND Link_active
 
 constraints:
   Link_maint_event_count:
@@ -138,54 +148,54 @@ constraints:
       `Link-maintcap_upper` — the build taken off is at most the chosen build in
       maintenance, and at most the build less its floor out of it
     dims: [scenario, snapshot, link]
-    where: Link_maintainable AND Link_p_nom_extendable AND NOT (Link_committable AND Link_p_nom_mod > 0) AND Link_active
+    where: Link_maint_ext
     expression: Link_maintenance_capacity <= Link_p_nom_ext - Link_p_nom_min * (1 - Link_maintenance)
   Link_maintcap_upper_nommax:
     description: "`Link-maintcap_upper_nommax` — out of maintenance, no build is taken off"
     dims: [scenario, snapshot, link]
-    where: Link_maintainable AND Link_p_nom_extendable AND NOT (Link_committable AND Link_p_nom_mod > 0) AND Link_active
+    where: Link_maint_ext
     expression: Link_maintenance_capacity <= Link_p_nom_max * Link_maintenance
   Link_maintcap_lower_nommax:
     description: "`Link-maintcap_lower_nommax` — in maintenance, the whole chosen build is taken off"
     dims: [scenario, snapshot, link]
-    where: Link_maintainable AND Link_p_nom_extendable AND NOT (Link_committable AND Link_p_nom_mod > 0) AND Link_active
+    where: Link_maint_ext
     expression: Link_maintenance_capacity >= Link_p_nom_ext - Link_p_nom_max * (1 - Link_maintenance)
   Link_maintcap_lower_nommin:
     description: "`Link-maintcap_lower_nommin` — in maintenance, at least the floor of the build is taken off"
     dims: [scenario, snapshot, link]
-    where: Link_maintainable AND Link_p_nom_extendable AND NOT (Link_committable AND Link_p_nom_mod > 0) AND Link_active AND Link_p_nom_min > 0
+    where: Link_maint_ext AND Link_p_nom_min > 0
     expression: Link_maintenance_capacity >= Link_p_nom_min * Link_maintenance
   Link_maint_status_le_status:
     description: "`Link-maint-status-le-status` — the status in maintenance is at most the status"
     dims: [scenario, snapshot, link]
-    where: Link_maintainable AND Link_committable AND NOT Link_p_nom_extendable AND NOT (Link_p_nom_mod > 0) AND Link_active
+    where: Link_maintainable AND Link_committed AND NOT Link_p_nom_extendable AND NOT (Link_p_nom_mod > 0)
     expression: Link_maintenance_status <= Link_status
   Link_maint_status_le_maint:
     description: "`Link-maint-status-le-maint` — out of maintenance, the status in maintenance is zero"
     dims: [scenario, snapshot, link]
-    where: Link_maintainable AND Link_committable AND NOT Link_p_nom_extendable AND NOT (Link_p_nom_mod > 0) AND Link_active
+    where: Link_maintainable AND Link_committed AND NOT Link_p_nom_extendable AND NOT (Link_p_nom_mod > 0)
     expression: Link_maintenance_status <= Link_maintenance
   Link_maint_status_lb:
     description: "`Link-maint-status-lb` — on and in maintenance, the status in maintenance is one"
     dims: [scenario, snapshot, link]
-    where: Link_maintainable AND Link_committable AND NOT Link_p_nom_extendable AND NOT (Link_p_nom_mod > 0) AND Link_active
+    where: Link_maintainable AND Link_committed AND NOT Link_p_nom_extendable AND NOT (Link_p_nom_mod > 0)
     expression: Link_maintenance_status >= Link_status + Link_maintenance - 1
   Link_maint_modstatus_le_status:
     description: "`Link-maint-modstatus-le-status` — the modules on in maintenance are at most the modules on"
     dims: [scenario, snapshot, link]
-    where: Link_maintainable AND Link_committable AND Link_p_nom_mod > 0 AND Link_active
+    where: Link_maintainable AND Link_committed AND Link_p_nom_mod > 0
     expression: Link_maintenance_status <= Link_status
   Link_maint_modstatus_le_maint:
     description: >-
       `Link-maint-modstatus-le-maint` — out of maintenance, no module is on in
       maintenance; in it, at most the modules the build cap holds
     dims: [scenario, snapshot, link]
-    where: Link_maintainable AND Link_committable AND Link_p_nom_mod > 0 AND Link_active
+    where: Link_maintainable AND Link_committed AND Link_p_nom_mod > 0
     expression: Link_maintenance_status <= Link_p_nom_max / Link_p_nom_mod * Link_maintenance
   Link_maint_modstatus_lb:
     description: "`Link-maint-modstatus-lb` — in maintenance, every module on is on in maintenance"
     dims: [scenario, snapshot, link]
-    where: Link_maintainable AND Link_committable AND Link_p_nom_mod > 0 AND Link_active
+    where: Link_maintainable AND Link_committed AND Link_p_nom_mod > 0
     expression: Link_maintenance_status >= Link_status - Link_p_nom_max / Link_p_nom_mod * (1 - Link_maintenance)
 
 assumptions:
@@ -272,6 +282,13 @@ assumptions:
 | $`\overline{\mathrm{f}}^{\mathrm{nom}}`$ | `Link_p_nom_max` over $`\Xi \times \mathcal{L}`$, data another file declares |
 | $`u^{f}`$ | `Link_status` over $`\Xi \times \mathcal{T} \times \mathcal{L}`$ |
 | $`F`$ | `Link_p_nom_ext` over $`\mathcal{L}`$ |
+| $`\mathrm{on}^{f,\mathrm{com}}`$ | `Link_committed` over $`\mathcal{T} \times \mathcal{L}`$, a mask another file defines |
+
+#### Masks
+
+| Symbol | Meaning |
+|---|---|
+| $`\mathrm{on}^{f,\mathrm{mnt,ext}}`$ | `Link_maint_ext` over $`\mathcal{T} \times \mathcal{L}`$ — a maintainable link with an extendable build, unless it is committable and modular, that stands in the snapshot's period — the maintenance rows against the chosen build |
 
 #### Subject to
 
@@ -296,61 +313,69 @@ assumptions:
 **`Link_maintcap_upper`**
 
 ```math
-\mu^{f,\mathrm{nom}}_{\xi,t,l} \le F_{l} - \underline{\mathrm{f}}^{\mathrm{nom}}_{\xi,l} \cdot \left( 1 - \mu^{f}_{\xi,t,l} \right) \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{mnt}^{f}_{l} \wedge \mathrm{ext}^{f}_{l} \wedge \neg \left( \mathrm{com}^{f}_{l} \wedge \mathrm{f}^{\mathrm{mod}}_{l} > 0 \right) \wedge \mathrm{on}^{f}_{t,l}
+\mu^{f,\mathrm{nom}}_{\xi,t,l} \le F_{l} - \underline{\mathrm{f}}^{\mathrm{nom}}_{\xi,l} \cdot \left( 1 - \mu^{f}_{\xi,t,l} \right) \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{on}^{f,\mathrm{mnt,ext}}_{t,l}
 ```
 
 **`Link_maintcap_upper_nommax`**
 
 ```math
-\mu^{f,\mathrm{nom}}_{\xi,t,l} \le \overline{\mathrm{f}}^{\mathrm{nom}}_{\xi,l} \cdot \mu^{f}_{\xi,t,l} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{mnt}^{f}_{l} \wedge \mathrm{ext}^{f}_{l} \wedge \neg \left( \mathrm{com}^{f}_{l} \wedge \mathrm{f}^{\mathrm{mod}}_{l} > 0 \right) \wedge \mathrm{on}^{f}_{t,l}
+\mu^{f,\mathrm{nom}}_{\xi,t,l} \le \overline{\mathrm{f}}^{\mathrm{nom}}_{\xi,l} \cdot \mu^{f}_{\xi,t,l} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{on}^{f,\mathrm{mnt,ext}}_{t,l}
 ```
 
 **`Link_maintcap_lower_nommax`**
 
 ```math
-\mu^{f,\mathrm{nom}}_{\xi,t,l} \ge F_{l} - \overline{\mathrm{f}}^{\mathrm{nom}}_{\xi,l} \cdot \left( 1 - \mu^{f}_{\xi,t,l} \right) \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{mnt}^{f}_{l} \wedge \mathrm{ext}^{f}_{l} \wedge \neg \left( \mathrm{com}^{f}_{l} \wedge \mathrm{f}^{\mathrm{mod}}_{l} > 0 \right) \wedge \mathrm{on}^{f}_{t,l}
+\mu^{f,\mathrm{nom}}_{\xi,t,l} \ge F_{l} - \overline{\mathrm{f}}^{\mathrm{nom}}_{\xi,l} \cdot \left( 1 - \mu^{f}_{\xi,t,l} \right) \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{on}^{f,\mathrm{mnt,ext}}_{t,l}
 ```
 
 **`Link_maintcap_lower_nommin`**
 
 ```math
-\mu^{f,\mathrm{nom}}_{\xi,t,l} \ge \underline{\mathrm{f}}^{\mathrm{nom}}_{\xi,l} \cdot \mu^{f}_{\xi,t,l} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{mnt}^{f}_{l} \wedge \mathrm{ext}^{f}_{l} \wedge \neg \left( \mathrm{com}^{f}_{l} \wedge \mathrm{f}^{\mathrm{mod}}_{l} > 0 \right) \wedge \mathrm{on}^{f}_{t,l} \wedge \underline{\mathrm{f}}^{\mathrm{nom}}_{\xi,l} > 0
+\mu^{f,\mathrm{nom}}_{\xi,t,l} \ge \underline{\mathrm{f}}^{\mathrm{nom}}_{\xi,l} \cdot \mu^{f}_{\xi,t,l} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{on}^{f,\mathrm{mnt,ext}}_{t,l} \wedge \underline{\mathrm{f}}^{\mathrm{nom}}_{\xi,l} > 0
 ```
 
 **`Link_maint_status_le_status`**
 
 ```math
-\mu^{f,u}_{\xi,t,l} \le u^{f}_{\xi,t,l} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{mnt}^{f}_{l} \wedge \mathrm{com}^{f}_{l} \wedge \neg \mathrm{ext}^{f}_{l} \wedge \neg \left( \mathrm{f}^{\mathrm{mod}}_{l} > 0 \right) \wedge \mathrm{on}^{f}_{t,l}
+\mu^{f,u}_{\xi,t,l} \le u^{f}_{\xi,t,l} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{mnt}^{f}_{l} \wedge \mathrm{on}^{f,\mathrm{com}}_{t,l} \wedge \neg \mathrm{ext}^{f}_{l} \wedge \neg \left( \mathrm{f}^{\mathrm{mod}}_{l} > 0 \right)
 ```
 
 **`Link_maint_status_le_maint`**
 
 ```math
-\mu^{f,u}_{\xi,t,l} \le \mu^{f}_{\xi,t,l} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{mnt}^{f}_{l} \wedge \mathrm{com}^{f}_{l} \wedge \neg \mathrm{ext}^{f}_{l} \wedge \neg \left( \mathrm{f}^{\mathrm{mod}}_{l} > 0 \right) \wedge \mathrm{on}^{f}_{t,l}
+\mu^{f,u}_{\xi,t,l} \le \mu^{f}_{\xi,t,l} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{mnt}^{f}_{l} \wedge \mathrm{on}^{f,\mathrm{com}}_{t,l} \wedge \neg \mathrm{ext}^{f}_{l} \wedge \neg \left( \mathrm{f}^{\mathrm{mod}}_{l} > 0 \right)
 ```
 
 **`Link_maint_status_lb`**
 
 ```math
-\mu^{f,u}_{\xi,t,l} \ge u^{f}_{\xi,t,l} + \mu^{f}_{\xi,t,l} - 1 \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{mnt}^{f}_{l} \wedge \mathrm{com}^{f}_{l} \wedge \neg \mathrm{ext}^{f}_{l} \wedge \neg \left( \mathrm{f}^{\mathrm{mod}}_{l} > 0 \right) \wedge \mathrm{on}^{f}_{t,l}
+\mu^{f,u}_{\xi,t,l} \ge u^{f}_{\xi,t,l} + \mu^{f}_{\xi,t,l} - 1 \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{mnt}^{f}_{l} \wedge \mathrm{on}^{f,\mathrm{com}}_{t,l} \wedge \neg \mathrm{ext}^{f}_{l} \wedge \neg \left( \mathrm{f}^{\mathrm{mod}}_{l} > 0 \right)
 ```
 
 **`Link_maint_modstatus_le_status`**
 
 ```math
-\mu^{f,u}_{\xi,t,l} \le u^{f}_{\xi,t,l} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{mnt}^{f}_{l} \wedge \mathrm{com}^{f}_{l} \wedge \mathrm{f}^{\mathrm{mod}}_{l} > 0 \wedge \mathrm{on}^{f}_{t,l}
+\mu^{f,u}_{\xi,t,l} \le u^{f}_{\xi,t,l} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{mnt}^{f}_{l} \wedge \mathrm{on}^{f,\mathrm{com}}_{t,l} \wedge \mathrm{f}^{\mathrm{mod}}_{l} > 0
 ```
 
 **`Link_maint_modstatus_le_maint`**
 
 ```math
-\mu^{f,u}_{\xi,t,l} \le \frac{\overline{\mathrm{f}}^{\mathrm{nom}}_{\xi,l}}{\mathrm{f}^{\mathrm{mod}}_{l}} \cdot \mu^{f}_{\xi,t,l} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{mnt}^{f}_{l} \wedge \mathrm{com}^{f}_{l} \wedge \mathrm{f}^{\mathrm{mod}}_{l} > 0 \wedge \mathrm{on}^{f}_{t,l}
+\mu^{f,u}_{\xi,t,l} \le \frac{\overline{\mathrm{f}}^{\mathrm{nom}}_{\xi,l}}{\mathrm{f}^{\mathrm{mod}}_{l}} \cdot \mu^{f}_{\xi,t,l} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{mnt}^{f}_{l} \wedge \mathrm{on}^{f,\mathrm{com}}_{t,l} \wedge \mathrm{f}^{\mathrm{mod}}_{l} > 0
 ```
 
 **`Link_maint_modstatus_lb`**
 
 ```math
-\mu^{f,u}_{\xi,t,l} \ge u^{f}_{\xi,t,l} - \frac{\overline{\mathrm{f}}^{\mathrm{nom}}_{\xi,l}}{\mathrm{f}^{\mathrm{mod}}_{l}} \cdot \left( 1 - \mu^{f}_{\xi,t,l} \right) \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{mnt}^{f}_{l} \wedge \mathrm{com}^{f}_{l} \wedge \mathrm{f}^{\mathrm{mod}}_{l} > 0 \wedge \mathrm{on}^{f}_{t,l}
+\mu^{f,u}_{\xi,t,l} \ge u^{f}_{\xi,t,l} - \frac{\overline{\mathrm{f}}^{\mathrm{nom}}_{\xi,l}}{\mathrm{f}^{\mathrm{mod}}_{l}} \cdot \left( 1 - \mu^{f}_{\xi,t,l} \right) \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{mnt}^{f}_{l} \wedge \mathrm{on}^{f,\mathrm{com}}_{t,l} \wedge \mathrm{f}^{\mathrm{mod}}_{l} > 0
+```
+
+#### Masks
+
+**`Link_maint_ext`**
+
+```math
+\mathrm{on}^{f,\mathrm{mnt,ext}}_{t,l} \iff \mathrm{mnt}^{f}_{l} \wedge \mathrm{ext}^{f}_{l} \wedge \neg \left( \mathrm{com}^{f}_{l} \wedge \mathrm{f}^{\mathrm{mod}}_{l} > 0 \right) \wedge \mathrm{on}^{f}_{t,l} \qquad \forall\, t \in \mathcal{T},\ l \in \mathcal{L}
 ```
 
 #### Variable domains
@@ -370,13 +395,13 @@ assumptions:
 **`Link_maintenance_capacity`**
 
 ```math
-\mu^{f,\mathrm{nom}}_{\xi,t,l} \ge 0 \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{mnt}^{f}_{l} \wedge \mathrm{ext}^{f}_{l} \wedge \neg \left( \mathrm{com}^{f}_{l} \wedge \mathrm{f}^{\mathrm{mod}}_{l} > 0 \right) \wedge \mathrm{on}^{f}_{t,l}
+\mu^{f,\mathrm{nom}}_{\xi,t,l} \ge 0 \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{on}^{f,\mathrm{mnt,ext}}_{t,l}
 ```
 
 **`Link_maintenance_status`**
 
 ```math
-\mu^{f,u}_{\xi,t,l} \ge 0 \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{mnt}^{f}_{l} \wedge \mathrm{com}^{f}_{l} \wedge \neg \left( \mathrm{ext}^{f}_{l} \wedge \neg \left( \mathrm{f}^{\mathrm{mod}}_{l} > 0 \right) \right) \wedge \mathrm{on}^{f}_{t,l}
+\mu^{f,u}_{\xi,t,l} \ge 0 \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{mnt}^{f}_{l} \wedge \mathrm{on}^{f,\mathrm{com}}_{t,l} \wedge \neg \left( \mathrm{ext}^{f}_{l} \wedge \neg \left( \mathrm{f}^{\mathrm{mod}}_{l} > 0 \right) \right)
 ```
 
 #### Assumptions
diff --git a/docs/examples/pypsa/link_ramping.md b/docs/examples/pypsa/link_ramping.md
index 3105ca16..41bc9db6 100644
--- a/docs/examples/pypsa/link_ramping.md
+++ b/docs/examples/pypsa/link_ramping.md
@@ -67,6 +67,8 @@ given:
     Link_p_nom_effective: { dims: [scenario, link] }
     Link_previous_status: { dims: [scenario, snapshot, link] }
     Link_p_nom_committed: { dims: [scenario, link] }
+  masks:
+    Link_com_ext: { dims: [snapshot, link] }
 
 expressions:
   Link_previous_p:
@@ -139,6 +141,16 @@ expressions:
           * (Link_previous_status - Link_status)
     otherwise: Link_ramp_down_rate * Link_p_nom_effective
 
+masks:
+  Link_ramps_from_previous:
+    description: >-
+      a snapshot whose ramp reads a previous output — any snapshot but its
+      period's first, and the horizon's first where the link comes in off or
+      carries an initial output
+    where: >-
+      position(snapshot, within=snapshot_period[period]) > 0 OR (position(snapshot) == 0 AND
+      (Link_status_initial == 0 OR Link_p_init))
+
 constraints:
   Link_p_ramp_limit_up_run_big_m:
     description: >-
@@ -146,11 +158,7 @@ constraints:
       raises flow no faster than its limit of the chosen build; the big M
       releases the row in the snapshot it turns on
     dims: [scenario, snapshot, link]
-    where: >-
-      Link_committable AND Link_p_nom_extendable AND NOT (Link_p_nom_mod > 0)
-      AND (Link_ramp_limit_up OR Link_ramp_limit_start_up)
-      AND (position(snapshot, within=snapshot_period[period]) > 0 OR (position(snapshot) == 0 AND (Link_status_initial == 0 OR Link_p_init)))
-      AND Link_active
+    where: Link_com_ext AND (Link_ramp_limit_up OR Link_ramp_limit_start_up) AND Link_ramps_from_previous
     expression: >-
       Link_p - Link_previous_p <=
       Link_ramp_up_rate * Link_p_nom_ext
@@ -161,11 +169,7 @@ constraints:
       committed extendable link ramps no further than its start-up ramp of
       the chosen build; the big M releases the row everywhere else
     dims: [scenario, snapshot, link]
-    where: >-
-      Link_committable AND Link_p_nom_extendable AND NOT (Link_p_nom_mod > 0)
-      AND (Link_ramp_limit_up OR Link_ramp_limit_start_up)
-      AND (position(snapshot, within=snapshot_period[period]) > 0 OR (position(snapshot) == 0 AND (Link_status_initial == 0 OR Link_p_init)))
-      AND Link_active
+    where: Link_com_ext AND (Link_ramp_limit_up OR Link_ramp_limit_start_up) AND Link_ramps_from_previous
     expression: >-
       Link_p - Link_previous_p <=
       Link_start_up_rate * Link_p_nom_ext
@@ -176,11 +180,7 @@ constraints:
       lowers flow no faster than its limit of the chosen build; the big M
       releases the row in the snapshot it turns off
     dims: [scenario, snapshot, link]
-    where: >-
-      Link_committable AND Link_p_nom_extendable AND NOT (Link_p_nom_mod > 0)
-      AND (Link_ramp_limit_down OR Link_ramp_limit_shut_down)
-      AND (position(snapshot, within=snapshot_period[period]) > 0 OR (position(snapshot) == 0 AND (Link_status_initial == 0 OR Link_p_init)))
-      AND Link_active
+    where: Link_com_ext AND (Link_ramp_limit_down OR Link_ramp_limit_shut_down) AND Link_ramps_from_previous
     expression: >-
       Link_previous_p - Link_p <=
       Link_ramp_down_rate * Link_p_nom_ext
@@ -191,11 +191,7 @@ constraints:
       a committed extendable link ramps no further than its shut-down ramp of
       the chosen build; the big M releases the row everywhere else
     dims: [scenario, snapshot, link]
-    where: >-
-      Link_committable AND Link_p_nom_extendable AND NOT (Link_p_nom_mod > 0)
-      AND (Link_ramp_limit_down OR Link_ramp_limit_shut_down)
-      AND (position(snapshot, within=snapshot_period[period]) > 0 OR (position(snapshot) == 0 AND (Link_status_initial == 0 OR Link_p_init)))
-      AND Link_active
+    where: Link_com_ext AND (Link_ramp_limit_down OR Link_ramp_limit_shut_down) AND Link_ramps_from_previous
     expression: >-
       Link_previous_p - Link_p <=
       Link_shut_down_rate * Link_p_nom_ext
@@ -212,7 +208,7 @@ constraints:
     where: >-
       (Link_ramp_limit_up OR Link_ramp_limit_start_up)
       AND NOT (Link_committable AND Link_p_nom_extendable AND NOT (Link_p_nom_mod > 0))
-      AND (position(snapshot, within=snapshot_period[period]) > 0 OR (position(snapshot) == 0 AND (Link_status_initial == 0 OR Link_p_init)))
+      AND Link_ramps_from_previous
       AND Link_active
     expression: Link_p - Link_previous_p <= Link_ramp_up_allowance
   Link_p_ramp_limit_down:
@@ -227,7 +223,7 @@ constraints:
     where: >-
       (Link_ramp_limit_down OR Link_ramp_limit_shut_down)
       AND NOT (Link_committable AND Link_p_nom_extendable AND NOT (Link_p_nom_mod > 0))
-      AND (position(snapshot, within=snapshot_period[period]) > 0 OR (position(snapshot) == 0 AND (Link_status_initial == 0 OR Link_p_init)))
+      AND Link_ramps_from_previous
       AND Link_active
     expression: Link_previous_p - Link_p <= Link_ramp_down_allowance
 
@@ -285,6 +281,7 @@ assumptions:
 | $`\widetilde{\mathrm{f}}^{\mathrm{nom}}`$ | `Link_p_nom_effective` over $`\Xi \times \mathcal{L}`$, an expression another file defines |
 | $`\overleftarrow{u}^{f}`$ | `Link_previous_status` over $`\Xi \times \mathcal{T} \times \mathcal{L}`$, an expression another file defines |
 | $`\widehat{\mathrm{f}}^{\mathrm{nom}}`$ | `Link_p_nom_committed` over $`\Xi \times \mathcal{L}`$, an expression another file defines |
+| $`\mathrm{on}^{f,\mathrm{com,ext}}`$ | `Link_com_ext` over $`\mathcal{T} \times \mathcal{L}`$, a mask another file defines |
 
 #### Definitions
 
@@ -298,6 +295,12 @@ assumptions:
 | $`\Delta^{f,+}`$ | `Link_ramp_up_allowance` over $`\Xi \times \mathcal{T} \times \mathcal{L}`$ — how far a link may raise flow between two snapshots — its ramp limit of the build while it stays on, plus its start-up ramp in the snapshot it turns on |
 | $`\Delta^{f,-}`$ | `Link_ramp_down_allowance` over $`\Xi \times \mathcal{T} \times \mathcal{L}`$ — how far a link may lower flow between two snapshots — its ramp limit of the build while it stays on, plus its shut-down ramp in the snapshot it turns off |
 
+#### Masks
+
+| Symbol | Meaning |
+|---|---|
+| $`\mathrm{prev}^{f}`$ | `Link_ramps_from_previous` over $`\Xi \times \mathcal{T} \times \mathcal{L}`$ — a snapshot whose ramp reads a previous output — any snapshot but its period's first, and the horizon's first where the link comes in off or carries an initial output |
+
 $`\mathrm{pos}(t)`$ denotes where index $`t`$ sits along its dimension's own order — the order `shift` steps along, not the order labels sort in — counted from $`0`$. The index itself stays the coordinate, so $`t`$ compares against labels and $`\mathrm{pos}(t)`$ against positions.
 
 $`\mathrm{pos}_{\mathrm{relation}(t)}(t)`$ counts within the group a relation puts $`t`$ in: the subscript names the map, $`\mathcal{T}_{\mathrm{relation}(t)}`$ is the group it lands in, and that group has a first position of its own.
@@ -307,37 +310,37 @@ $`\mathrm{pos}_{\mathrm{relation}(t)}(t)`$ counts within the group a relation pu
 **`Link_p_ramp_limit_up_run_big_m`**
 
 ```math
-f_{\xi,t,l} - \overleftarrow{f}_{\xi,t,l} \le \widetilde{\mathrm{ru}}^{f}_{\xi,t,l} \cdot F_{l} + \mathrm{M}^{f}_{\xi,l} - \mathrm{M}^{f}_{\xi,l} \cdot \overleftarrow{u}^{f}_{\xi,t,l} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{com}^{f}_{l} \wedge \mathrm{ext}^{f}_{l} \wedge \neg \left( \mathrm{f}^{\mathrm{mod}}_{l} > 0 \right) \wedge \left( \mathrm{ru}^{f}_{\xi,t,l} \text{ is defined} \vee \mathrm{ru}^{f,\mathrm{up}}_{\xi,l} \text{ is defined} \right) \wedge \left( \mathrm{pos}_{\mathrm{snapshot\_period}(t)}(t) > 0 \vee \mathrm{pos}(t) = 0 \wedge \left( \mathrm{u}^{f,0}_{\xi,l} = 0 \vee \mathrm{f}^{0}_{\xi,l} \text{ is defined} \right) \right) \wedge \mathrm{on}^{f}_{t,l}
+f_{\xi,t,l} - \overleftarrow{f}_{\xi,t,l} \le \widetilde{\mathrm{ru}}^{f}_{\xi,t,l} \cdot F_{l} + \mathrm{M}^{f}_{\xi,l} - \mathrm{M}^{f}_{\xi,l} \cdot \overleftarrow{u}^{f}_{\xi,t,l} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{on}^{f,\mathrm{com,ext}}_{t,l} \wedge \left( \mathrm{ru}^{f}_{\xi,t,l} \text{ is defined} \vee \mathrm{ru}^{f,\mathrm{up}}_{\xi,l} \text{ is defined} \right) \wedge \mathrm{prev}^{f}_{\xi,t,l}
 ```
 
 **`Link_p_ramp_limit_up_start_big_m`**
 
 ```math
-f_{\xi,t,l} - \overleftarrow{f}_{\xi,t,l} \le \widetilde{\mathrm{ru}}^{f,\mathrm{up}}_{\xi,l} \cdot F_{l} + \mathrm{M}^{f}_{\xi,l} - \mathrm{M}^{f}_{\xi,l} \cdot \mathit{up}^{f}_{\xi,t,l} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{com}^{f}_{l} \wedge \mathrm{ext}^{f}_{l} \wedge \neg \left( \mathrm{f}^{\mathrm{mod}}_{l} > 0 \right) \wedge \left( \mathrm{ru}^{f}_{\xi,t,l} \text{ is defined} \vee \mathrm{ru}^{f,\mathrm{up}}_{\xi,l} \text{ is defined} \right) \wedge \left( \mathrm{pos}_{\mathrm{snapshot\_period}(t)}(t) > 0 \vee \mathrm{pos}(t) = 0 \wedge \left( \mathrm{u}^{f,0}_{\xi,l} = 0 \vee \mathrm{f}^{0}_{\xi,l} \text{ is defined} \right) \right) \wedge \mathrm{on}^{f}_{t,l}
+f_{\xi,t,l} - \overleftarrow{f}_{\xi,t,l} \le \widetilde{\mathrm{ru}}^{f,\mathrm{up}}_{\xi,l} \cdot F_{l} + \mathrm{M}^{f}_{\xi,l} - \mathrm{M}^{f}_{\xi,l} \cdot \mathit{up}^{f}_{\xi,t,l} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{on}^{f,\mathrm{com,ext}}_{t,l} \wedge \left( \mathrm{ru}^{f}_{\xi,t,l} \text{ is defined} \vee \mathrm{ru}^{f,\mathrm{up}}_{\xi,l} \text{ is defined} \right) \wedge \mathrm{prev}^{f}_{\xi,t,l}
 ```
 
 **`Link_p_ramp_limit_down_run_big_m`**
 
 ```math
-\overleftarrow{f}_{\xi,t,l} - f_{\xi,t,l} \le \widetilde{\mathrm{rd}}^{f}_{\xi,t,l} \cdot F_{l} + \mathrm{M}^{f}_{\xi,l} - \mathrm{M}^{f}_{\xi,l} \cdot u^{f}_{\xi,t,l} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{com}^{f}_{l} \wedge \mathrm{ext}^{f}_{l} \wedge \neg \left( \mathrm{f}^{\mathrm{mod}}_{l} > 0 \right) \wedge \left( \mathrm{rd}^{f}_{\xi,t,l} \text{ is defined} \vee \mathrm{rd}^{f,\mathrm{dn}}_{\xi,l} \text{ is defined} \right) \wedge \left( \mathrm{pos}_{\mathrm{snapshot\_period}(t)}(t) > 0 \vee \mathrm{pos}(t) = 0 \wedge \left( \mathrm{u}^{f,0}_{\xi,l} = 0 \vee \mathrm{f}^{0}_{\xi,l} \text{ is defined} \right) \right) \wedge \mathrm{on}^{f}_{t,l}
+\overleftarrow{f}_{\xi,t,l} - f_{\xi,t,l} \le \widetilde{\mathrm{rd}}^{f}_{\xi,t,l} \cdot F_{l} + \mathrm{M}^{f}_{\xi,l} - \mathrm{M}^{f}_{\xi,l} \cdot u^{f}_{\xi,t,l} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{on}^{f,\mathrm{com,ext}}_{t,l} \wedge \left( \mathrm{rd}^{f}_{\xi,t,l} \text{ is defined} \vee \mathrm{rd}^{f,\mathrm{dn}}_{\xi,l} \text{ is defined} \right) \wedge \mathrm{prev}^{f}_{\xi,t,l}
 ```
 
 **`Link_p_ramp_limit_down_shut_big_m`**
 
 ```math
-\overleftarrow{f}_{\xi,t,l} - f_{\xi,t,l} \le \widetilde{\mathrm{rd}}^{f,\mathrm{dn}}_{\xi,l} \cdot F_{l} + \mathrm{M}^{f}_{\xi,l} - \mathrm{M}^{f}_{\xi,l} \cdot \mathit{dn}^{f}_{\xi,t,l} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{com}^{f}_{l} \wedge \mathrm{ext}^{f}_{l} \wedge \neg \left( \mathrm{f}^{\mathrm{mod}}_{l} > 0 \right) \wedge \left( \mathrm{rd}^{f}_{\xi,t,l} \text{ is defined} \vee \mathrm{rd}^{f,\mathrm{dn}}_{\xi,l} \text{ is defined} \right) \wedge \left( \mathrm{pos}_{\mathrm{snapshot\_period}(t)}(t) > 0 \vee \mathrm{pos}(t) = 0 \wedge \left( \mathrm{u}^{f,0}_{\xi,l} = 0 \vee \mathrm{f}^{0}_{\xi,l} \text{ is defined} \right) \right) \wedge \mathrm{on}^{f}_{t,l}
+\overleftarrow{f}_{\xi,t,l} - f_{\xi,t,l} \le \widetilde{\mathrm{rd}}^{f,\mathrm{dn}}_{\xi,l} \cdot F_{l} + \mathrm{M}^{f}_{\xi,l} - \mathrm{M}^{f}_{\xi,l} \cdot \mathit{dn}^{f}_{\xi,t,l} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{on}^{f,\mathrm{com,ext}}_{t,l} \wedge \left( \mathrm{rd}^{f}_{\xi,t,l} \text{ is defined} \vee \mathrm{rd}^{f,\mathrm{dn}}_{\xi,l} \text{ is defined} \right) \wedge \mathrm{prev}^{f}_{\xi,t,l}
 ```
 
 **`Link_p_ramp_limit_up`**
 
 ```math
-f_{\xi,t,l} - \overleftarrow{f}_{\xi,t,l} \le \Delta^{f,+}_{\xi,t,l} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \left( \mathrm{ru}^{f}_{\xi,t,l} \text{ is defined} \vee \mathrm{ru}^{f,\mathrm{up}}_{\xi,l} \text{ is defined} \right) \wedge \neg \left( \mathrm{com}^{f}_{l} \wedge \mathrm{ext}^{f}_{l} \wedge \neg \left( \mathrm{f}^{\mathrm{mod}}_{l} > 0 \right) \right) \wedge \left( \mathrm{pos}_{\mathrm{snapshot\_period}(t)}(t) > 0 \vee \mathrm{pos}(t) = 0 \wedge \left( \mathrm{u}^{f,0}_{\xi,l} = 0 \vee \mathrm{f}^{0}_{\xi,l} \text{ is defined} \right) \right) \wedge \mathrm{on}^{f}_{t,l}
+f_{\xi,t,l} - \overleftarrow{f}_{\xi,t,l} \le \Delta^{f,+}_{\xi,t,l} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \left( \mathrm{ru}^{f}_{\xi,t,l} \text{ is defined} \vee \mathrm{ru}^{f,\mathrm{up}}_{\xi,l} \text{ is defined} \right) \wedge \neg \left( \mathrm{com}^{f}_{l} \wedge \mathrm{ext}^{f}_{l} \wedge \neg \left( \mathrm{f}^{\mathrm{mod}}_{l} > 0 \right) \right) \wedge \mathrm{prev}^{f}_{\xi,t,l} \wedge \mathrm{on}^{f}_{t,l}
 ```
 
 **`Link_p_ramp_limit_down`**
 
 ```math
-\overleftarrow{f}_{\xi,t,l} - f_{\xi,t,l} \le \Delta^{f,-}_{\xi,t,l} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \left( \mathrm{rd}^{f}_{\xi,t,l} \text{ is defined} \vee \mathrm{rd}^{f,\mathrm{dn}}_{\xi,l} \text{ is defined} \right) \wedge \neg \left( \mathrm{com}^{f}_{l} \wedge \mathrm{ext}^{f}_{l} \wedge \neg \left( \mathrm{f}^{\mathrm{mod}}_{l} > 0 \right) \right) \wedge \left( \mathrm{pos}_{\mathrm{snapshot\_period}(t)}(t) > 0 \vee \mathrm{pos}(t) = 0 \wedge \left( \mathrm{u}^{f,0}_{\xi,l} = 0 \vee \mathrm{f}^{0}_{\xi,l} \text{ is defined} \right) \right) \wedge \mathrm{on}^{f}_{t,l}
+\overleftarrow{f}_{\xi,t,l} - f_{\xi,t,l} \le \Delta^{f,-}_{\xi,t,l} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \left( \mathrm{rd}^{f}_{\xi,t,l} \text{ is defined} \vee \mathrm{rd}^{f,\mathrm{dn}}_{\xi,l} \text{ is defined} \right) \wedge \neg \left( \mathrm{com}^{f}_{l} \wedge \mathrm{ext}^{f}_{l} \wedge \neg \left( \mathrm{f}^{\mathrm{mod}}_{l} > 0 \right) \right) \wedge \mathrm{prev}^{f}_{\xi,t,l} \wedge \mathrm{on}^{f}_{t,l}
 ```
 
 #### Definitions
@@ -384,6 +387,14 @@ f_{\xi,t,l} - \overleftarrow{f}_{\xi,t,l} \le \Delta^{f,+}_{\xi,t,l} \qquad \for
 \Delta^{f,-}_{\xi,t,l} = \begin{cases} \widetilde{\mathrm{rd}}^{f}_{\xi,t,l} \cdot \widehat{\mathrm{f}}^{\mathrm{nom}}_{\xi,l} \cdot u^{f}_{\xi,t,l} + \widetilde{\mathrm{rd}}^{f,\mathrm{dn}}_{\xi,l} \cdot \widehat{\mathrm{f}}^{\mathrm{nom}}_{\xi,l} \cdot \left( \overleftarrow{u}^{f}_{\xi,t,l} - u^{f}_{\xi,t,l} \right) & \text{if } \mathrm{com}^{f}_{l} \\ \widetilde{\mathrm{rd}}^{f}_{\xi,t,l} \cdot \widetilde{\mathrm{f}}^{\mathrm{nom}}_{\xi,l} & \text{otherwise} \end{cases} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L}
 ```
 
+#### Masks
+
+**`Link_ramps_from_previous`**
+
+```math
+\mathrm{prev}^{f}_{\xi,t,l} \iff \mathrm{pos}_{\mathrm{snapshot\_period}(t)}(t) > 0 \vee \mathrm{pos}(t) = 0 \wedge \left( \mathrm{u}^{f,0}_{\xi,l} = 0 \vee \mathrm{f}^{0}_{\xi,l} \text{ is defined} \right) \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L}
+```
+
 #### Assumptions
 
 **`Link_came_in_running_unless_committable`**
diff --git a/docs/examples/pypsa/process.md b/docs/examples/pypsa/process.md
index 39a06c4e..19757167 100644
--- a/docs/examples/pypsa/process.md
+++ b/docs/examples/pypsa/process.md
@@ -245,6 +245,13 @@ expressions:
       sum(Process_output_arrival, over=process_output, by=Process_output_bus[bus])
     adds_to: Bus_injection
 
+masks:
+  Process_committed:
+    description: >-
+      a committable process that stands in the snapshot's period — every
+      unit-commitment row's set
+    where: Process_committable AND Process_active
+
 constraints:
   Process_fix_p_lower:
     description: "`Process-fix-p-lower` — a fixed process runs at least its minimum, negative for the other way"
@@ -381,6 +388,12 @@ assumptions:
 | $`\mathit{Process\_additions}`$ | `Process_additions` over $`\mathcal{Y} \times \mathcal{I}`$ |
 | $`\mathit{Process\_injection}`$ | `Process_injection` over $`\Xi \times \mathcal{T} \times \mathcal{N}`$ |
 
+#### Masks
+
+| Symbol | Meaning |
+|---|---|
+| $`\mathrm{on}^{z,\mathrm{com}}`$ | `Process_committed` over $`\mathcal{T} \times \mathcal{J}`$ — a committable process that stands in the snapshot's period — every unit-commitment row's set |
+
 $`t \ominus k`$ denotes cyclic translation: index $`t-k`$ taken modulo the size of the dimension (`roll`). Plain $`t-k`$ (`shift`) has no wraparound — terms translated past the edge are simply absent.
 
 $`t \boxminus_{v} k`$ denotes translation with $`v`$ standing where index $`t-k`$ leaves the dimension (`shift(edge=v)`), so the row at that boundary is built and carries $`v`$ rather than being dropped.
@@ -493,6 +506,14 @@ z_{\xi,t,j} = \mathrm{z}^{\mathrm{set}}_{\xi,t,j} \qquad \forall\, \xi \in \Xi,\
 \mathit{Process\_injection}_{\xi,t,n} = \sum_{r \in \mathcal{R} \,:\, \mathrm{Process\_output\_bus}(r) = n} \overrightarrow{z}_{\xi,t,r} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ n \in \mathcal{N}
 ```
 
+#### Masks
+
+**`Process_committed`**
+
+```math
+\mathrm{on}^{z,\mathrm{com}}_{t,j} \iff \mathrm{com}^{z}_{j} \wedge \mathrm{on}^{z}_{t,j} \qquad \forall\, t \in \mathcal{T},\ j \in \mathcal{J}
+```
+
 #### Variable domains
 
 **`Process_p`**
diff --git a/docs/examples/pypsa/process_commitment.md b/docs/examples/pypsa/process_commitment.md
index b68a58d8..97d8f13f 100644
--- a/docs/examples/pypsa/process_commitment.md
+++ b/docs/examples/pypsa/process_commitment.md
@@ -88,21 +88,21 @@ variables:
       the rows below cap at one, or at the module count where the build is
       modular
     dims: [scenario, snapshot, process]
-    where: Process_committable AND Process_active
+    where: Process_committed
     domain: integer
     bounds:
       lower: 0
   Process_start_up:
     description: "`Process-start_up` — how much of a committable process turns on this snapshot, capped as the status is"
     dims: [scenario, snapshot, process]
-    where: Process_committable AND Process_active
+    where: Process_committed
     domain: integer
     bounds:
       lower: 0
   Process_shut_down:
     description: "`Process-shut_down` — how much of a committable process turns off this snapshot, capped as the status is"
     dims: [scenario, snapshot, process]
-    where: Process_committable AND Process_active
+    where: Process_committed
     domain: integer
     bounds:
       lower: 0
@@ -128,6 +128,8 @@ given:
     Process_p_nom_ext: { dims: [process] }
   expressions:
     scenario_opex: { dims: [scenario] }
+  masks:
+    Process_committed: { dims: [snapshot, process] }
 
 expressions:
   Process_previous_status:
@@ -155,26 +157,38 @@ expressions:
       + sum(sum(Process_shut_down * Process_shut_down_cost, over=process), over=snapshot)
     adds_to: scenario_opex
 
+masks:
+  Process_com_ext:
+    description: >-
+      a committable process with an extendable, non-modular build that stands
+      in the snapshot's period — PyPSA's `com-ext` rows, whose status is
+      relaxed against the chosen build
+    where: >-
+      Process_committable
+      AND Process_p_nom_extendable
+      AND NOT (Process_p_nom_mod > 0)
+      AND Process_active
+
 constraints:
   Process_com_p_lower:
     description: "`Process-com-p-lower` — a committed process runs at least its minimum; off, at least nothing"
     dims: [scenario, snapshot, process]
-    where: Process_committable AND not Process_p_nom_extendable AND NOT (Process_p_nom_mod > 0) AND Process_active
+    where: Process_committed AND NOT Process_p_nom_extendable AND NOT (Process_p_nom_mod > 0)
     expression: Process_p >= Process_p_min_pu * Process_p_nom * (Process_status - Process_maintenance_pu * Process_maintenance_status)
   Process_com_p_upper:
     description: "`Process-com-p-upper` — a committed process runs at most what is available; off, at most nothing"
     dims: [scenario, snapshot, process]
-    where: Process_committable AND not Process_p_nom_extendable AND NOT (Process_p_nom_mod > 0) AND Process_active
+    where: Process_committed AND NOT Process_p_nom_extendable AND NOT (Process_p_nom_mod > 0)
     expression: Process_p <= Process_p_max_pu * Process_p_nom * (Process_status - Process_maintenance_pu * Process_maintenance_status)
   Process_com_transition_start_up:
     description: "`Process-com-transition-start-up` — turning on is a start, counted against the state the process carried into the snapshot"
     dims: [scenario, snapshot, process]
-    where: Process_committable AND Process_active
+    where: Process_committed
     expression: Process_start_up >= Process_status - Process_previous_status
   Process_com_transition_shut_down:
     description: "`Process-com-transition-shut-down` — turning off is a stop, counted against the state the process carried into the snapshot"
     dims: [scenario, snapshot, process]
-    where: Process_committable AND Process_active
+    where: Process_committed
     expression: Process_shut_down >= Process_previous_status - Process_status
   Process_com_up_time:
     description: >-
@@ -182,7 +196,7 @@ constraints:
       is still on. The first snapshot's share of the window is the brought-in
       up time's, which the must-stay-up mask carries
     dims: [scenario, snapshot, process]
-    where: Process_committable AND Process_min_up_time > 0 AND position(snapshot) > 0 AND Process_active
+    where: Process_committed AND Process_min_up_time > 0 AND position(snapshot) > 0
     expression: sum_back(Process_start_up, along=snapshot, window=Process_min_up_time) <= Process_status
   Process_com_down_time:
     description: >-
@@ -190,38 +204,38 @@ constraints:
       time is still off. The first snapshot's share of the window is the
       brought-in down time's, which the must-stay-down mask carries
     dims: [scenario, snapshot, process]
-    where: Process_committable AND Process_min_down_time > 0 AND position(snapshot) > 0 AND Process_active
+    where: Process_committed AND Process_min_down_time > 0 AND position(snapshot) > 0
     expression: sum_back(Process_shut_down, along=snapshot, window=Process_min_down_time) <= 1 - Process_status
   Process_com_status_must_stay_up:
     description: "`Process-com-status-min_up_time_must_stay_up` — a process still serving the up time it brought in stays on"
     dims: [scenario, snapshot, process]
-    where: Process_committable AND Process_must_stay_up AND Process_active
+    where: Process_committed AND Process_must_stay_up
     expression: Process_status == 1
   Process_com_status_must_stay_down:
     description: >-
       `Process-com-status-min_down_time_must_stay_up` — a process still serving
       the down time it brought in stays off; PyPSA names the row `_must_stay_up`
     dims: [scenario, snapshot, process]
-    where: Process_committable AND Process_must_stay_down AND Process_active
+    where: Process_committed AND Process_must_stay_down
     expression: Process_status == 0
   Process_com_ext_p_upper_cap:
     description: >-
       `Process-com-ext-p-upper-cap` — a committed extendable process runs
       at most what is available of the chosen build, whatever its status
     dims: [scenario, snapshot, process]
-    where: Process_committable AND Process_p_nom_extendable AND NOT (Process_p_nom_mod > 0) AND Process_active
+    where: Process_com_ext
     expression: Process_p <= Process_p_max_pu * (Process_p_nom_ext - Process_maintenance_pu * Process_maintenance_capacity)
   Process_com_ext_p_upper_big_m:
     description: "`Process-com-ext-p-upper-bigM` — off, a process does not run; on, the big M is no bound"
     dims: [scenario, snapshot, process]
-    where: Process_committable AND Process_p_nom_extendable AND NOT (Process_p_nom_mod > 0) AND Process_active
+    where: Process_com_ext
     expression: Process_p <= Process_big_m * Process_status
   Process_com_ext_p_lower:
     description: >-
       `Process-com-ext-p-lower` — a committed extendable process runs at
       least its minimum of the chosen build; off, the big M releases the row
     dims: [scenario, snapshot, process]
-    where: Process_committable AND Process_p_nom_extendable AND NOT (Process_p_nom_mod > 0) AND Process_active
+    where: Process_com_ext
     expression: >-
       Process_p >=
       Process_p_min_pu * (Process_p_nom_ext - Process_maintenance_pu * Process_maintenance_capacity)
@@ -232,23 +246,21 @@ constraints:
       negative, internal power is also plainly non-negative, a row the big-M lower
       cannot assert while the process is off
     dims: [scenario, snapshot, process]
-    where: >-
-      Process_committable AND Process_p_nom_extendable
-      AND Process_p_min_pu_nonneg AND NOT (Process_p_nom_mod > 0) AND Process_active
+    where: Process_com_ext AND Process_p_min_pu_nonneg
     expression: Process_p >= 0
   Process_com_mod_p_lower:
     description: >-
       `Process-com-mod-p-lower` — a committed modular process runs at least
       its minimum of one module, whether the build is fixed or a decision
     dims: [scenario, snapshot, process]
-    where: Process_committable AND Process_p_nom_mod > 0 AND Process_active
+    where: Process_committed AND Process_p_nom_mod > 0
     expression: Process_p >= Process_p_min_pu * Process_p_nom_mod * (Process_status - Process_maintenance_pu * Process_maintenance_status)
   Process_com_mod_p_upper:
     description: >-
       `Process-com-mod-p-upper` — a committed modular process runs at most
       one module's share, whether the build is fixed or a decision
     dims: [scenario, snapshot, process]
-    where: Process_committable AND Process_p_nom_mod > 0 AND Process_active
+    where: Process_committed AND Process_p_nom_mod > 0
     expression: Process_p <= Process_p_max_pu * Process_p_nom_mod * (Process_status - Process_maintenance_pu * Process_maintenance_status)
   Process_status_p_fixed_upper:
     description: >-
@@ -256,7 +268,7 @@ constraints:
       place, an explicit row as PyPSA writes it: one where the build is not
       modular, and the fixed build's whole count of modules where it is
     dims: [scenario, snapshot, process]
-    where: Process_committable AND NOT (Process_p_nom_extendable AND Process_p_nom_mod > 0) AND Process_active
+    where: Process_committed AND NOT (Process_p_nom_extendable AND Process_p_nom_mod > 0)
     expression: Process_status <= Process_modules_installed
   Process_start_up_p_fixed_upper:
     description: >-
@@ -264,7 +276,7 @@ constraints:
       place, an explicit row as PyPSA writes it: one where the build is not
       modular, and the fixed build's whole count of modules where it is
     dims: [scenario, snapshot, process]
-    where: Process_committable AND NOT (Process_p_nom_extendable AND Process_p_nom_mod > 0) AND Process_active
+    where: Process_committed AND NOT (Process_p_nom_extendable AND Process_p_nom_mod > 0)
     expression: Process_start_up <= Process_modules_installed
   Process_shut_down_p_fixed_upper:
     description: >-
@@ -272,22 +284,22 @@ constraints:
       place, an explicit row as PyPSA writes it: one where the build is not
       modular, and the fixed build's whole count of modules where it is
     dims: [scenario, snapshot, process]
-    where: Process_committable AND NOT (Process_p_nom_extendable AND Process_p_nom_mod > 0) AND Process_active
+    where: Process_committed AND NOT (Process_p_nom_extendable AND Process_p_nom_mod > 0)
     expression: Process_shut_down <= Process_modules_installed
   Process_status_p_nom_variable_upper:
     description: "`Process-status-p_nom-variable-upper` — a modular process is on only where a module is built"
     dims: [scenario, snapshot, process]
-    where: Process_committable AND Process_p_nom_extendable AND Process_p_nom_mod > 0 AND Process_active
+    where: Process_committed AND Process_p_nom_extendable AND Process_p_nom_mod > 0
     expression: Process_status <= Process_n_mod
   Process_start_up_p_nom_variable_upper:
     description: "`Process-start_up-p_nom-variable-upper` — a modular process starts only where a module is built"
     dims: [scenario, snapshot, process]
-    where: Process_committable AND Process_p_nom_extendable AND Process_p_nom_mod > 0 AND Process_active
+    where: Process_committed AND Process_p_nom_extendable AND Process_p_nom_mod > 0
     expression: Process_start_up <= Process_n_mod
   Process_shut_down_p_nom_variable_upper:
     description: "`Process-shut_down-p_nom-variable-upper` — a modular process stops only where a module is built"
     dims: [scenario, snapshot, process]
-    where: Process_committable AND Process_p_nom_extendable AND Process_p_nom_mod > 0 AND Process_active
+    where: Process_committed AND Process_p_nom_extendable AND Process_p_nom_mod > 0
     expression: Process_shut_down <= Process_n_mod
 ```
 
@@ -344,6 +356,7 @@ constraints:
 | $`\mu^{z,u}`$ | `Process_maintenance_status` over $`\Xi \times \mathcal{T} \times \mathcal{J}`$ |
 | $`Z`$ | `Process_p_nom_ext` over $`\mathcal{J}`$ |
 | $`\mathit{scenario\_opex}`$ | `scenario_opex` over $`\Xi`$, an expression this file adds `Process_commitment_opex` to |
+| $`\mathrm{on}^{z,\mathrm{com}}`$ | `Process_committed` over $`\mathcal{T} \times \mathcal{J}`$, a mask another file defines |
 
 #### Definitions
 
@@ -353,6 +366,12 @@ constraints:
 | $`\overleftarrow{u}^{\circ z}`$ | `Process_status_carried_over` over $`\Xi \times \mathcal{T} \times \mathcal{J}`$ — the state a process carries over into a snapshot — the state it brought into the horizon at the first, the previous snapshot's after that |
 | $`\mathit{Process\_commitment\_opex}`$ | `Process_commitment_opex` over $`\Xi`$ |
 
+#### Masks
+
+| Symbol | Meaning |
+|---|---|
+| $`\mathrm{on}^{z,\mathrm{com,ext}}`$ | `Process_com_ext` over $`\mathcal{T} \times \mathcal{J}`$ — a committable process with an extendable, non-modular build that stands in the snapshot's period — PyPSA's `com-ext` rows, whose status is relaxed against the chosen build |
+
 $`\mathrm{pos}(t)`$ denotes where index $`t`$ sits along its dimension's own order — the order `shift` steps along, not the order labels sort in — counted from $`0`$. The index itself stays the coordinate, so $`t`$ compares against labels and $`\mathrm{pos}(t)`$ against positions.
 
 #### Subject to
@@ -360,121 +379,121 @@ $`\mathrm{pos}(t)`$ denotes where index $`t`$ sits along its dimension's own ord
 **`Process_com_p_lower`**
 
 ```math
-z_{\xi,t,j} \ge \underline{\mathrm{z}}_{\xi,t,j} \cdot \mathrm{z}^{\mathrm{nom}}_{\xi,j} \cdot \left( u^{z}_{\xi,t,j} - \gamma^{z}_{\xi,j} \cdot \mu^{z,u}_{\xi,t,j} \right) \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{com}^{z}_{j} \wedge \neg \mathrm{ext}^{z}_{j} \wedge \neg \left( \mathrm{z}^{\mathrm{mod}}_{j} > 0 \right) \wedge \mathrm{on}^{z}_{t,j}
+z_{\xi,t,j} \ge \underline{\mathrm{z}}_{\xi,t,j} \cdot \mathrm{z}^{\mathrm{nom}}_{\xi,j} \cdot \left( u^{z}_{\xi,t,j} - \gamma^{z}_{\xi,j} \cdot \mu^{z,u}_{\xi,t,j} \right) \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{on}^{z,\mathrm{com}}_{t,j} \wedge \neg \mathrm{ext}^{z}_{j} \wedge \neg \left( \mathrm{z}^{\mathrm{mod}}_{j} > 0 \right)
 ```
 
 **`Process_com_p_upper`**
 
 ```math
-z_{\xi,t,j} \le \overline{\mathrm{z}}_{\xi,t,j} \cdot \mathrm{z}^{\mathrm{nom}}_{\xi,j} \cdot \left( u^{z}_{\xi,t,j} - \gamma^{z}_{\xi,j} \cdot \mu^{z,u}_{\xi,t,j} \right) \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{com}^{z}_{j} \wedge \neg \mathrm{ext}^{z}_{j} \wedge \neg \left( \mathrm{z}^{\mathrm{mod}}_{j} > 0 \right) \wedge \mathrm{on}^{z}_{t,j}
+z_{\xi,t,j} \le \overline{\mathrm{z}}_{\xi,t,j} \cdot \mathrm{z}^{\mathrm{nom}}_{\xi,j} \cdot \left( u^{z}_{\xi,t,j} - \gamma^{z}_{\xi,j} \cdot \mu^{z,u}_{\xi,t,j} \right) \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{on}^{z,\mathrm{com}}_{t,j} \wedge \neg \mathrm{ext}^{z}_{j} \wedge \neg \left( \mathrm{z}^{\mathrm{mod}}_{j} > 0 \right)
 ```
 
 **`Process_com_transition_start_up`**
 
 ```math
-\mathit{up}^{z}_{\xi,t,j} \ge u^{z}_{\xi,t,j} - \overleftarrow{u}^{z}_{\xi,t,j} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{com}^{z}_{j} \wedge \mathrm{on}^{z}_{t,j}
+\mathit{up}^{z}_{\xi,t,j} \ge u^{z}_{\xi,t,j} - \overleftarrow{u}^{z}_{\xi,t,j} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{on}^{z,\mathrm{com}}_{t,j}
 ```
 
 **`Process_com_transition_shut_down`**
 
 ```math
-\mathit{dn}^{z}_{\xi,t,j} \ge \overleftarrow{u}^{z}_{\xi,t,j} - u^{z}_{\xi,t,j} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{com}^{z}_{j} \wedge \mathrm{on}^{z}_{t,j}
+\mathit{dn}^{z}_{\xi,t,j} \ge \overleftarrow{u}^{z}_{\xi,t,j} - u^{z}_{\xi,t,j} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{on}^{z,\mathrm{com}}_{t,j}
 ```
 
 **`Process_com_up_time`**
 
 ```math
-\sum_{t' \in \mathcal{T} \,:\, 0 \le t - t' < \mathrm{UT}^{z}} \mathit{up}^{z}_{\xi,t',j} \le u^{z}_{\xi,t,j} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{com}^{z}_{j} \wedge \mathrm{UT}^{z}_{\xi,j} > 0 \wedge \mathrm{pos}(t) > 0 \wedge \mathrm{on}^{z}_{t,j}
+\sum_{t' \in \mathcal{T} \,:\, 0 \le t - t' < \mathrm{UT}^{z}} \mathit{up}^{z}_{\xi,t',j} \le u^{z}_{\xi,t,j} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{on}^{z,\mathrm{com}}_{t,j} \wedge \mathrm{UT}^{z}_{\xi,j} > 0 \wedge \mathrm{pos}(t) > 0
 ```
 
 **`Process_com_down_time`**
 
 ```math
-\sum_{t' \in \mathcal{T} \,:\, 0 \le t - t' < \mathrm{DT}^{z}} \mathit{dn}^{z}_{\xi,t',j} \le 1 - u^{z}_{\xi,t,j} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{com}^{z}_{j} \wedge \mathrm{DT}^{z}_{\xi,j} > 0 \wedge \mathrm{pos}(t) > 0 \wedge \mathrm{on}^{z}_{t,j}
+\sum_{t' \in \mathcal{T} \,:\, 0 \le t - t' < \mathrm{DT}^{z}} \mathit{dn}^{z}_{\xi,t',j} \le 1 - u^{z}_{\xi,t,j} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{on}^{z,\mathrm{com}}_{t,j} \wedge \mathrm{DT}^{z}_{\xi,j} > 0 \wedge \mathrm{pos}(t) > 0
 ```
 
 **`Process_com_status_must_stay_up`**
 
 ```math
-u^{z}_{\xi,t,j} = 1 \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{com}^{z}_{j} \wedge \mathrm{hold}^{z}_{\xi,t,j} \wedge \mathrm{on}^{z}_{t,j}
+u^{z}_{\xi,t,j} = 1 \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{on}^{z,\mathrm{com}}_{t,j} \wedge \mathrm{hold}^{z}_{\xi,t,j}
 ```
 
 **`Process_com_status_must_stay_down`**
 
 ```math
-u^{z}_{\xi,t,j} = 0 \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{com}^{z}_{j} \wedge \mathrm{rest}^{z}_{\xi,t,j} \wedge \mathrm{on}^{z}_{t,j}
+u^{z}_{\xi,t,j} = 0 \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{on}^{z,\mathrm{com}}_{t,j} \wedge \mathrm{rest}^{z}_{\xi,t,j}
 ```
 
 **`Process_com_ext_p_upper_cap`**
 
 ```math
-z_{\xi,t,j} \le \overline{\mathrm{z}}_{\xi,t,j} \cdot \left( Z_{j} - \gamma^{z}_{\xi,j} \cdot \mu^{z,\mathrm{nom}}_{\xi,t,j} \right) \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{com}^{z}_{j} \wedge \mathrm{ext}^{z}_{j} \wedge \neg \left( \mathrm{z}^{\mathrm{mod}}_{j} > 0 \right) \wedge \mathrm{on}^{z}_{t,j}
+z_{\xi,t,j} \le \overline{\mathrm{z}}_{\xi,t,j} \cdot \left( Z_{j} - \gamma^{z}_{\xi,j} \cdot \mu^{z,\mathrm{nom}}_{\xi,t,j} \right) \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{on}^{z,\mathrm{com,ext}}_{t,j}
 ```
 
 **`Process_com_ext_p_upper_big_m`**
 
 ```math
-z_{\xi,t,j} \le \mathrm{M}^{z}_{\xi,j} \cdot u^{z}_{\xi,t,j} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{com}^{z}_{j} \wedge \mathrm{ext}^{z}_{j} \wedge \neg \left( \mathrm{z}^{\mathrm{mod}}_{j} > 0 \right) \wedge \mathrm{on}^{z}_{t,j}
+z_{\xi,t,j} \le \mathrm{M}^{z}_{\xi,j} \cdot u^{z}_{\xi,t,j} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{on}^{z,\mathrm{com,ext}}_{t,j}
 ```
 
 **`Process_com_ext_p_lower`**
 
 ```math
-z_{\xi,t,j} \ge \underline{\mathrm{z}}_{\xi,t,j} \cdot \left( Z_{j} - \gamma^{z}_{\xi,j} \cdot \mu^{z,\mathrm{nom}}_{\xi,t,j} \right) + \mathrm{M}^{z}_{\xi,j} \cdot u^{z}_{\xi,t,j} - \mathrm{M}^{z}_{\xi,j} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{com}^{z}_{j} \wedge \mathrm{ext}^{z}_{j} \wedge \neg \left( \mathrm{z}^{\mathrm{mod}}_{j} > 0 \right) \wedge \mathrm{on}^{z}_{t,j}
+z_{\xi,t,j} \ge \underline{\mathrm{z}}_{\xi,t,j} \cdot \left( Z_{j} - \gamma^{z}_{\xi,j} \cdot \mu^{z,\mathrm{nom}}_{\xi,t,j} \right) + \mathrm{M}^{z}_{\xi,j} \cdot u^{z}_{\xi,t,j} - \mathrm{M}^{z}_{\xi,j} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{on}^{z,\mathrm{com,ext}}_{t,j}
 ```
 
 **`Process_com_ext_p_lower_nonneg`**
 
 ```math
-z_{\xi,t,j} \ge 0 \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{com}^{z}_{j} \wedge \mathrm{ext}^{z}_{j} \wedge \mathrm{nonneg}^{z}_{j} \wedge \neg \left( \mathrm{z}^{\mathrm{mod}}_{j} > 0 \right) \wedge \mathrm{on}^{z}_{t,j}
+z_{\xi,t,j} \ge 0 \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{on}^{z,\mathrm{com,ext}}_{t,j} \wedge \mathrm{nonneg}^{z}_{j}
 ```
 
 **`Process_com_mod_p_lower`**
 
 ```math
-z_{\xi,t,j} \ge \underline{\mathrm{z}}_{\xi,t,j} \cdot \mathrm{z}^{\mathrm{mod}}_{j} \cdot \left( u^{z}_{\xi,t,j} - \gamma^{z}_{\xi,j} \cdot \mu^{z,u}_{\xi,t,j} \right) \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{com}^{z}_{j} \wedge \mathrm{z}^{\mathrm{mod}}_{j} > 0 \wedge \mathrm{on}^{z}_{t,j}
+z_{\xi,t,j} \ge \underline{\mathrm{z}}_{\xi,t,j} \cdot \mathrm{z}^{\mathrm{mod}}_{j} \cdot \left( u^{z}_{\xi,t,j} - \gamma^{z}_{\xi,j} \cdot \mu^{z,u}_{\xi,t,j} \right) \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{on}^{z,\mathrm{com}}_{t,j} \wedge \mathrm{z}^{\mathrm{mod}}_{j} > 0
 ```
 
 **`Process_com_mod_p_upper`**
 
 ```math
-z_{\xi,t,j} \le \overline{\mathrm{z}}_{\xi,t,j} \cdot \mathrm{z}^{\mathrm{mod}}_{j} \cdot \left( u^{z}_{\xi,t,j} - \gamma^{z}_{\xi,j} \cdot \mu^{z,u}_{\xi,t,j} \right) \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{com}^{z}_{j} \wedge \mathrm{z}^{\mathrm{mod}}_{j} > 0 \wedge \mathrm{on}^{z}_{t,j}
+z_{\xi,t,j} \le \overline{\mathrm{z}}_{\xi,t,j} \cdot \mathrm{z}^{\mathrm{mod}}_{j} \cdot \left( u^{z}_{\xi,t,j} - \gamma^{z}_{\xi,j} \cdot \mu^{z,u}_{\xi,t,j} \right) \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{on}^{z,\mathrm{com}}_{t,j} \wedge \mathrm{z}^{\mathrm{mod}}_{j} > 0
 ```
 
 **`Process_status_p_fixed_upper`**
 
 ```math
-u^{z}_{\xi,t,j} \le \mathrm{N}^{z,\mathrm{fix}}_{\xi,j} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{com}^{z}_{j} \wedge \neg \left( \mathrm{ext}^{z}_{j} \wedge \mathrm{z}^{\mathrm{mod}}_{j} > 0 \right) \wedge \mathrm{on}^{z}_{t,j}
+u^{z}_{\xi,t,j} \le \mathrm{N}^{z,\mathrm{fix}}_{\xi,j} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{on}^{z,\mathrm{com}}_{t,j} \wedge \neg \left( \mathrm{ext}^{z}_{j} \wedge \mathrm{z}^{\mathrm{mod}}_{j} > 0 \right)
 ```
 
 **`Process_start_up_p_fixed_upper`**
 
 ```math
-\mathit{up}^{z}_{\xi,t,j} \le \mathrm{N}^{z,\mathrm{fix}}_{\xi,j} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{com}^{z}_{j} \wedge \neg \left( \mathrm{ext}^{z}_{j} \wedge \mathrm{z}^{\mathrm{mod}}_{j} > 0 \right) \wedge \mathrm{on}^{z}_{t,j}
+\mathit{up}^{z}_{\xi,t,j} \le \mathrm{N}^{z,\mathrm{fix}}_{\xi,j} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{on}^{z,\mathrm{com}}_{t,j} \wedge \neg \left( \mathrm{ext}^{z}_{j} \wedge \mathrm{z}^{\mathrm{mod}}_{j} > 0 \right)
 ```
 
 **`Process_shut_down_p_fixed_upper`**
 
 ```math
-\mathit{dn}^{z}_{\xi,t,j} \le \mathrm{N}^{z,\mathrm{fix}}_{\xi,j} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{com}^{z}_{j} \wedge \neg \left( \mathrm{ext}^{z}_{j} \wedge \mathrm{z}^{\mathrm{mod}}_{j} > 0 \right) \wedge \mathrm{on}^{z}_{t,j}
+\mathit{dn}^{z}_{\xi,t,j} \le \mathrm{N}^{z,\mathrm{fix}}_{\xi,j} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{on}^{z,\mathrm{com}}_{t,j} \wedge \neg \left( \mathrm{ext}^{z}_{j} \wedge \mathrm{z}^{\mathrm{mod}}_{j} > 0 \right)
 ```
 
 **`Process_status_p_nom_variable_upper`**
 
 ```math
-u^{z}_{\xi,t,j} \le N^{z}_{j} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{com}^{z}_{j} \wedge \mathrm{ext}^{z}_{j} \wedge \mathrm{z}^{\mathrm{mod}}_{j} > 0 \wedge \mathrm{on}^{z}_{t,j}
+u^{z}_{\xi,t,j} \le N^{z}_{j} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{on}^{z,\mathrm{com}}_{t,j} \wedge \mathrm{ext}^{z}_{j} \wedge \mathrm{z}^{\mathrm{mod}}_{j} > 0
 ```
 
 **`Process_start_up_p_nom_variable_upper`**
 
 ```math
-\mathit{up}^{z}_{\xi,t,j} \le N^{z}_{j} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{com}^{z}_{j} \wedge \mathrm{ext}^{z}_{j} \wedge \mathrm{z}^{\mathrm{mod}}_{j} > 0 \wedge \mathrm{on}^{z}_{t,j}
+\mathit{up}^{z}_{\xi,t,j} \le N^{z}_{j} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{on}^{z,\mathrm{com}}_{t,j} \wedge \mathrm{ext}^{z}_{j} \wedge \mathrm{z}^{\mathrm{mod}}_{j} > 0
 ```
 
 **`Process_shut_down_p_nom_variable_upper`**
 
 ```math
-\mathit{dn}^{z}_{\xi,t,j} \le N^{z}_{j} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{com}^{z}_{j} \wedge \mathrm{ext}^{z}_{j} \wedge \mathrm{z}^{\mathrm{mod}}_{j} > 0 \wedge \mathrm{on}^{z}_{t,j}
+\mathit{dn}^{z}_{\xi,t,j} \le N^{z}_{j} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{on}^{z,\mathrm{com}}_{t,j} \wedge \mathrm{ext}^{z}_{j} \wedge \mathrm{z}^{\mathrm{mod}}_{j} > 0
 ```
 
 #### Definitions
@@ -497,23 +516,31 @@ u^{z}_{\xi,t,j} \le N^{z}_{j} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\
 \mathit{Process\_commitment\_opex}_{\xi} = \sum_{t \in \mathcal{T}} \sum_{j \in \mathcal{J}} u^{z}_{\xi,t,j} \cdot \mathrm{c}^{z,\mathrm{on}}_{\xi,t,j} \cdot \mathrm{w}_{t} \cdot \mathrm{w}^{y}_{\mathrm{snapshot\_period}(t)} + \sum_{t \in \mathcal{T}} \sum_{j \in \mathcal{J}} \mathit{up}^{z}_{\xi,t,j} \cdot \mathrm{c}^{z,\mathrm{up}}_{\xi,t,j} + \sum_{t \in \mathcal{T}} \sum_{j \in \mathcal{J}} \mathit{dn}^{z}_{\xi,t,j} \cdot \mathrm{c}^{z,\mathrm{dn}}_{\xi,t,j} \qquad \forall\, \xi \in \Xi
 ```
 
+#### Masks
+
+**`Process_com_ext`**
+
+```math
+\mathrm{on}^{z,\mathrm{com,ext}}_{t,j} \iff \mathrm{com}^{z}_{j} \wedge \mathrm{ext}^{z}_{j} \wedge \neg \left( \mathrm{z}^{\mathrm{mod}}_{j} > 0 \right) \wedge \mathrm{on}^{z}_{t,j} \qquad \forall\, t \in \mathcal{T},\ j \in \mathcal{J}
+```
+
 #### Variable domains
 
 **`Process_status`**
 
 ```math
-u^{z}_{\xi,t,j} \ge 0, u^{z}_{\xi,t,j} \in \mathbb{Z} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{com}^{z}_{j} \wedge \mathrm{on}^{z}_{t,j}
+u^{z}_{\xi,t,j} \ge 0, u^{z}_{\xi,t,j} \in \mathbb{Z} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{on}^{z,\mathrm{com}}_{t,j}
 ```
 
 **`Process_start_up`**
 
 ```math
-\mathit{up}^{z}_{\xi,t,j} \ge 0, \mathit{up}^{z}_{\xi,t,j} \in \mathbb{Z} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{com}^{z}_{j} \wedge \mathrm{on}^{z}_{t,j}
+\mathit{up}^{z}_{\xi,t,j} \ge 0, \mathit{up}^{z}_{\xi,t,j} \in \mathbb{Z} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{on}^{z,\mathrm{com}}_{t,j}
 ```
 
 **`Process_shut_down`**
 
 ```math
-\mathit{dn}^{z}_{\xi,t,j} \ge 0, \mathit{dn}^{z}_{\xi,t,j} \in \mathbb{Z} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{com}^{z}_{j} \wedge \mathrm{on}^{z}_{t,j}
+\mathit{dn}^{z}_{\xi,t,j} \ge 0, \mathit{dn}^{z}_{\xi,t,j} \in \mathbb{Z} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{on}^{z,\mathrm{com}}_{t,j}
 ```
 <!-- gallery:end -->
diff --git a/docs/examples/pypsa/process_maintenance.md b/docs/examples/pypsa/process_maintenance.md
index 33bb93a0..ea2b545a 100644
--- a/docs/examples/pypsa/process_maintenance.md
+++ b/docs/examples/pypsa/process_maintenance.md
@@ -82,9 +82,7 @@ variables:
       `Process-maintenance_capacity` — the chosen build while in maintenance, zero
       otherwise: the product the `maintcap` rows linearize
     dims: [scenario, snapshot, process]
-    where: >-
-      Process_maintainable AND Process_p_nom_extendable
-      AND NOT (Process_committable AND Process_p_nom_mod > 0) AND Process_active
+    where: Process_maint_ext
     absence: zero
     bounds:
       lower: 0
@@ -95,8 +93,9 @@ variables:
       maintenance may also be off
     dims: [scenario, snapshot, process]
     where: >-
-      Process_maintainable AND Process_committable
-      AND NOT (Process_p_nom_extendable AND NOT (Process_p_nom_mod > 0)) AND Process_active
+      Process_maintainable
+      AND Process_committed
+      AND NOT (Process_p_nom_extendable AND NOT (Process_p_nom_mod > 0))
     absence: zero
     bounds:
       lower: 0
@@ -113,6 +112,20 @@ given:
   variables:
     Process_status: { dims: [scenario, snapshot, process], domain: integer }
     Process_p_nom_ext: { dims: [process] }
+  masks:
+    Process_committed: { dims: [snapshot, process] }
+
+masks:
+  Process_maint_ext:
+    description: >-
+      a maintainable process with an extendable build, unless it is
+      committable and modular, that stands in the snapshot's period — the
+      maintenance rows against the chosen build
+    where: >-
+      Process_maintainable
+      AND Process_p_nom_extendable
+      AND NOT (Process_committable AND Process_p_nom_mod > 0)
+      AND Process_active
 
 constraints:
   Process_maint_event_count:
@@ -138,54 +151,54 @@ constraints:
       `Process-maintcap_upper` — the build taken off is at most the chosen build in
       maintenance, and at most the build less its floor out of it
     dims: [scenario, snapshot, process]
-    where: Process_maintainable AND Process_p_nom_extendable AND NOT (Process_committable AND Process_p_nom_mod > 0) AND Process_active
+    where: Process_maint_ext
     expression: Process_maintenance_capacity <= Process_p_nom_ext - Process_p_nom_min * (1 - Process_maintenance)
   Process_maintcap_upper_nommax:
     description: "`Process-maintcap_upper_nommax` — out of maintenance, no build is taken off"
     dims: [scenario, snapshot, process]
-    where: Process_maintainable AND Process_p_nom_extendable AND NOT (Process_committable AND Process_p_nom_mod > 0) AND Process_active
+    where: Process_maint_ext
     expression: Process_maintenance_capacity <= Process_p_nom_max * Process_maintenance
   Process_maintcap_lower_nommax:
     description: "`Process-maintcap_lower_nommax` — in maintenance, the whole chosen build is taken off"
     dims: [scenario, snapshot, process]
-    where: Process_maintainable AND Process_p_nom_extendable AND NOT (Process_committable AND Process_p_nom_mod > 0) AND Process_active
+    where: Process_maint_ext
     expression: Process_maintenance_capacity >= Process_p_nom_ext - Process_p_nom_max * (1 - Process_maintenance)
   Process_maintcap_lower_nommin:
     description: "`Process-maintcap_lower_nommin` — in maintenance, at least the floor of the build is taken off"
     dims: [scenario, snapshot, process]
-    where: Process_maintainable AND Process_p_nom_extendable AND NOT (Process_committable AND Process_p_nom_mod > 0) AND Process_active AND Process_p_nom_min > 0
+    where: Process_maint_ext AND Process_p_nom_min > 0
     expression: Process_maintenance_capacity >= Process_p_nom_min * Process_maintenance
   Process_maint_status_le_status:
     description: "`Process-maint-status-le-status` — the status in maintenance is at most the status"
     dims: [scenario, snapshot, process]
-    where: Process_maintainable AND Process_committable AND NOT Process_p_nom_extendable AND NOT (Process_p_nom_mod > 0) AND Process_active
+    where: Process_maintainable AND Process_committed AND NOT Process_p_nom_extendable AND NOT (Process_p_nom_mod > 0)
     expression: Process_maintenance_status <= Process_status
   Process_maint_status_le_maint:
     description: "`Process-maint-status-le-maint` — out of maintenance, the status in maintenance is zero"
     dims: [scenario, snapshot, process]
-    where: Process_maintainable AND Process_committable AND NOT Process_p_nom_extendable AND NOT (Process_p_nom_mod > 0) AND Process_active
+    where: Process_maintainable AND Process_committed AND NOT Process_p_nom_extendable AND NOT (Process_p_nom_mod > 0)
     expression: Process_maintenance_status <= Process_maintenance
   Process_maint_status_lb:
     description: "`Process-maint-status-lb` — on and in maintenance, the status in maintenance is one"
     dims: [scenario, snapshot, process]
-    where: Process_maintainable AND Process_committable AND NOT Process_p_nom_extendable AND NOT (Process_p_nom_mod > 0) AND Process_active
+    where: Process_maintainable AND Process_committed AND NOT Process_p_nom_extendable AND NOT (Process_p_nom_mod > 0)
     expression: Process_maintenance_status >= Process_status + Process_maintenance - 1
   Process_maint_modstatus_le_status:
     description: "`Process-maint-modstatus-le-status` — the modules on in maintenance are at most the modules on"
     dims: [scenario, snapshot, process]
-    where: Process_maintainable AND Process_committable AND Process_p_nom_mod > 0 AND Process_active
+    where: Process_maintainable AND Process_committed AND Process_p_nom_mod > 0
     expression: Process_maintenance_status <= Process_status
   Process_maint_modstatus_le_maint:
     description: >-
       `Process-maint-modstatus-le-maint` — out of maintenance, no module is on in
       maintenance; in it, at most the modules the build cap holds
     dims: [scenario, snapshot, process]
-    where: Process_maintainable AND Process_committable AND Process_p_nom_mod > 0 AND Process_active
+    where: Process_maintainable AND Process_committed AND Process_p_nom_mod > 0
     expression: Process_maintenance_status <= Process_p_nom_max / Process_p_nom_mod * Process_maintenance
   Process_maint_modstatus_lb:
     description: "`Process-maint-modstatus-lb` — in maintenance, every module on is on in maintenance"
     dims: [scenario, snapshot, process]
-    where: Process_maintainable AND Process_committable AND Process_p_nom_mod > 0 AND Process_active
+    where: Process_maintainable AND Process_committed AND Process_p_nom_mod > 0
     expression: Process_maintenance_status >= Process_status - Process_p_nom_max / Process_p_nom_mod * (1 - Process_maintenance)
 
 assumptions:
@@ -272,6 +285,13 @@ assumptions:
 | $`\mathrm{w}^{\mathrm{gen}}`$ | `snapshot_weightings_generators` over $`\mathcal{T}`$, data another file declares |
 | $`u^{z}`$ | `Process_status` over $`\Xi \times \mathcal{T} \times \mathcal{J}`$ |
 | $`Z`$ | `Process_p_nom_ext` over $`\mathcal{J}`$ |
+| $`\mathrm{on}^{z,\mathrm{com}}`$ | `Process_committed` over $`\mathcal{T} \times \mathcal{J}`$, a mask another file defines |
+
+#### Masks
+
+| Symbol | Meaning |
+|---|---|
+| $`\mathrm{on}^{z,\mathrm{mnt,ext}}`$ | `Process_maint_ext` over $`\mathcal{T} \times \mathcal{J}`$ — a maintainable process with an extendable build, unless it is committable and modular, that stands in the snapshot's period — the maintenance rows against the chosen build |
 
 #### Subject to
 
@@ -296,61 +316,69 @@ assumptions:
 **`Process_maintcap_upper`**
 
 ```math
-\mu^{z,\mathrm{nom}}_{\xi,t,j} \le Z_{j} - \underline{\mathrm{z}}^{\mathrm{nom}}_{\xi,j} \cdot \left( 1 - \mu^{z}_{\xi,t,j} \right) \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{mnt}^{z}_{j} \wedge \mathrm{ext}^{z}_{j} \wedge \neg \left( \mathrm{com}^{z}_{j} \wedge \mathrm{z}^{\mathrm{mod}}_{j} > 0 \right) \wedge \mathrm{on}^{z}_{t,j}
+\mu^{z,\mathrm{nom}}_{\xi,t,j} \le Z_{j} - \underline{\mathrm{z}}^{\mathrm{nom}}_{\xi,j} \cdot \left( 1 - \mu^{z}_{\xi,t,j} \right) \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{on}^{z,\mathrm{mnt,ext}}_{t,j}
 ```
 
 **`Process_maintcap_upper_nommax`**
 
 ```math
-\mu^{z,\mathrm{nom}}_{\xi,t,j} \le \overline{\mathrm{z}}^{\mathrm{nom}}_{\xi,j} \cdot \mu^{z}_{\xi,t,j} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{mnt}^{z}_{j} \wedge \mathrm{ext}^{z}_{j} \wedge \neg \left( \mathrm{com}^{z}_{j} \wedge \mathrm{z}^{\mathrm{mod}}_{j} > 0 \right) \wedge \mathrm{on}^{z}_{t,j}
+\mu^{z,\mathrm{nom}}_{\xi,t,j} \le \overline{\mathrm{z}}^{\mathrm{nom}}_{\xi,j} \cdot \mu^{z}_{\xi,t,j} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{on}^{z,\mathrm{mnt,ext}}_{t,j}
 ```
 
 **`Process_maintcap_lower_nommax`**
 
 ```math
-\mu^{z,\mathrm{nom}}_{\xi,t,j} \ge Z_{j} - \overline{\mathrm{z}}^{\mathrm{nom}}_{\xi,j} \cdot \left( 1 - \mu^{z}_{\xi,t,j} \right) \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{mnt}^{z}_{j} \wedge \mathrm{ext}^{z}_{j} \wedge \neg \left( \mathrm{com}^{z}_{j} \wedge \mathrm{z}^{\mathrm{mod}}_{j} > 0 \right) \wedge \mathrm{on}^{z}_{t,j}
+\mu^{z,\mathrm{nom}}_{\xi,t,j} \ge Z_{j} - \overline{\mathrm{z}}^{\mathrm{nom}}_{\xi,j} \cdot \left( 1 - \mu^{z}_{\xi,t,j} \right) \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{on}^{z,\mathrm{mnt,ext}}_{t,j}
 ```
 
 **`Process_maintcap_lower_nommin`**
 
 ```math
-\mu^{z,\mathrm{nom}}_{\xi,t,j} \ge \underline{\mathrm{z}}^{\mathrm{nom}}_{\xi,j} \cdot \mu^{z}_{\xi,t,j} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{mnt}^{z}_{j} \wedge \mathrm{ext}^{z}_{j} \wedge \neg \left( \mathrm{com}^{z}_{j} \wedge \mathrm{z}^{\mathrm{mod}}_{j} > 0 \right) \wedge \mathrm{on}^{z}_{t,j} \wedge \underline{\mathrm{z}}^{\mathrm{nom}}_{\xi,j} > 0
+\mu^{z,\mathrm{nom}}_{\xi,t,j} \ge \underline{\mathrm{z}}^{\mathrm{nom}}_{\xi,j} \cdot \mu^{z}_{\xi,t,j} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{on}^{z,\mathrm{mnt,ext}}_{t,j} \wedge \underline{\mathrm{z}}^{\mathrm{nom}}_{\xi,j} > 0
 ```
 
 **`Process_maint_status_le_status`**
 
 ```math
-\mu^{z,u}_{\xi,t,j} \le u^{z}_{\xi,t,j} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{mnt}^{z}_{j} \wedge \mathrm{com}^{z}_{j} \wedge \neg \mathrm{ext}^{z}_{j} \wedge \neg \left( \mathrm{z}^{\mathrm{mod}}_{j} > 0 \right) \wedge \mathrm{on}^{z}_{t,j}
+\mu^{z,u}_{\xi,t,j} \le u^{z}_{\xi,t,j} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{mnt}^{z}_{j} \wedge \mathrm{on}^{z,\mathrm{com}}_{t,j} \wedge \neg \mathrm{ext}^{z}_{j} \wedge \neg \left( \mathrm{z}^{\mathrm{mod}}_{j} > 0 \right)
 ```
 
 **`Process_maint_status_le_maint`**
 
 ```math
-\mu^{z,u}_{\xi,t,j} \le \mu^{z}_{\xi,t,j} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{mnt}^{z}_{j} \wedge \mathrm{com}^{z}_{j} \wedge \neg \mathrm{ext}^{z}_{j} \wedge \neg \left( \mathrm{z}^{\mathrm{mod}}_{j} > 0 \right) \wedge \mathrm{on}^{z}_{t,j}
+\mu^{z,u}_{\xi,t,j} \le \mu^{z}_{\xi,t,j} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{mnt}^{z}_{j} \wedge \mathrm{on}^{z,\mathrm{com}}_{t,j} \wedge \neg \mathrm{ext}^{z}_{j} \wedge \neg \left( \mathrm{z}^{\mathrm{mod}}_{j} > 0 \right)
 ```
 
 **`Process_maint_status_lb`**
 
 ```math
-\mu^{z,u}_{\xi,t,j} \ge u^{z}_{\xi,t,j} + \mu^{z}_{\xi,t,j} - 1 \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{mnt}^{z}_{j} \wedge \mathrm{com}^{z}_{j} \wedge \neg \mathrm{ext}^{z}_{j} \wedge \neg \left( \mathrm{z}^{\mathrm{mod}}_{j} > 0 \right) \wedge \mathrm{on}^{z}_{t,j}
+\mu^{z,u}_{\xi,t,j} \ge u^{z}_{\xi,t,j} + \mu^{z}_{\xi,t,j} - 1 \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{mnt}^{z}_{j} \wedge \mathrm{on}^{z,\mathrm{com}}_{t,j} \wedge \neg \mathrm{ext}^{z}_{j} \wedge \neg \left( \mathrm{z}^{\mathrm{mod}}_{j} > 0 \right)
 ```
 
 **`Process_maint_modstatus_le_status`**
 
 ```math
-\mu^{z,u}_{\xi,t,j} \le u^{z}_{\xi,t,j} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{mnt}^{z}_{j} \wedge \mathrm{com}^{z}_{j} \wedge \mathrm{z}^{\mathrm{mod}}_{j} > 0 \wedge \mathrm{on}^{z}_{t,j}
+\mu^{z,u}_{\xi,t,j} \le u^{z}_{\xi,t,j} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{mnt}^{z}_{j} \wedge \mathrm{on}^{z,\mathrm{com}}_{t,j} \wedge \mathrm{z}^{\mathrm{mod}}_{j} > 0
 ```
 
 **`Process_maint_modstatus_le_maint`**
 
 ```math
-\mu^{z,u}_{\xi,t,j} \le \frac{\overline{\mathrm{z}}^{\mathrm{nom}}_{\xi,j}}{\mathrm{z}^{\mathrm{mod}}_{j}} \cdot \mu^{z}_{\xi,t,j} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{mnt}^{z}_{j} \wedge \mathrm{com}^{z}_{j} \wedge \mathrm{z}^{\mathrm{mod}}_{j} > 0 \wedge \mathrm{on}^{z}_{t,j}
+\mu^{z,u}_{\xi,t,j} \le \frac{\overline{\mathrm{z}}^{\mathrm{nom}}_{\xi,j}}{\mathrm{z}^{\mathrm{mod}}_{j}} \cdot \mu^{z}_{\xi,t,j} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{mnt}^{z}_{j} \wedge \mathrm{on}^{z,\mathrm{com}}_{t,j} \wedge \mathrm{z}^{\mathrm{mod}}_{j} > 0
 ```
 
 **`Process_maint_modstatus_lb`**
 
 ```math
-\mu^{z,u}_{\xi,t,j} \ge u^{z}_{\xi,t,j} - \frac{\overline{\mathrm{z}}^{\mathrm{nom}}_{\xi,j}}{\mathrm{z}^{\mathrm{mod}}_{j}} \cdot \left( 1 - \mu^{z}_{\xi,t,j} \right) \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{mnt}^{z}_{j} \wedge \mathrm{com}^{z}_{j} \wedge \mathrm{z}^{\mathrm{mod}}_{j} > 0 \wedge \mathrm{on}^{z}_{t,j}
+\mu^{z,u}_{\xi,t,j} \ge u^{z}_{\xi,t,j} - \frac{\overline{\mathrm{z}}^{\mathrm{nom}}_{\xi,j}}{\mathrm{z}^{\mathrm{mod}}_{j}} \cdot \left( 1 - \mu^{z}_{\xi,t,j} \right) \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{mnt}^{z}_{j} \wedge \mathrm{on}^{z,\mathrm{com}}_{t,j} \wedge \mathrm{z}^{\mathrm{mod}}_{j} > 0
+```
+
+#### Masks
+
+**`Process_maint_ext`**
+
+```math
+\mathrm{on}^{z,\mathrm{mnt,ext}}_{t,j} \iff \mathrm{mnt}^{z}_{j} \wedge \mathrm{ext}^{z}_{j} \wedge \neg \left( \mathrm{com}^{z}_{j} \wedge \mathrm{z}^{\mathrm{mod}}_{j} > 0 \right) \wedge \mathrm{on}^{z}_{t,j} \qquad \forall\, t \in \mathcal{T},\ j \in \mathcal{J}
 ```
 
 #### Variable domains
@@ -370,13 +398,13 @@ assumptions:
 **`Process_maintenance_capacity`**
 
 ```math
-\mu^{z,\mathrm{nom}}_{\xi,t,j} \ge 0 \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{mnt}^{z}_{j} \wedge \mathrm{ext}^{z}_{j} \wedge \neg \left( \mathrm{com}^{z}_{j} \wedge \mathrm{z}^{\mathrm{mod}}_{j} > 0 \right) \wedge \mathrm{on}^{z}_{t,j}
+\mu^{z,\mathrm{nom}}_{\xi,t,j} \ge 0 \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{on}^{z,\mathrm{mnt,ext}}_{t,j}
 ```
 
 **`Process_maintenance_status`**
 
 ```math
-\mu^{z,u}_{\xi,t,j} \ge 0 \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{mnt}^{z}_{j} \wedge \mathrm{com}^{z}_{j} \wedge \neg \left( \mathrm{ext}^{z}_{j} \wedge \neg \left( \mathrm{z}^{\mathrm{mod}}_{j} > 0 \right) \right) \wedge \mathrm{on}^{z}_{t,j}
+\mu^{z,u}_{\xi,t,j} \ge 0 \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{mnt}^{z}_{j} \wedge \mathrm{on}^{z,\mathrm{com}}_{t,j} \wedge \neg \left( \mathrm{ext}^{z}_{j} \wedge \neg \left( \mathrm{z}^{\mathrm{mod}}_{j} > 0 \right) \right)
 ```
 
 #### Assumptions
diff --git a/docs/examples/pypsa/process_ramping.md b/docs/examples/pypsa/process_ramping.md
index 65c24d92..eaeb5ea5 100644
--- a/docs/examples/pypsa/process_ramping.md
+++ b/docs/examples/pypsa/process_ramping.md
@@ -67,6 +67,8 @@ given:
     Process_p_nom_effective: { dims: [scenario, process] }
     Process_previous_status: { dims: [scenario, snapshot, process] }
     Process_p_nom_committed: { dims: [scenario, process] }
+  masks:
+    Process_com_ext: { dims: [snapshot, process] }
 
 expressions:
   Process_previous_p:
@@ -139,6 +141,16 @@ expressions:
           * (Process_previous_status - Process_status)
     otherwise: Process_ramp_down_rate * Process_p_nom_effective
 
+masks:
+  Process_ramps_from_previous:
+    description: >-
+      a snapshot whose ramp reads a previous output — any snapshot but its
+      period's first, and the horizon's first where the process comes in off
+      or carries an initial output
+    where: >-
+      position(snapshot, within=snapshot_period[period]) > 0 OR (position(snapshot) == 0 AND
+      (Process_status_initial == 0 OR Process_p_init))
+
 constraints:
   Process_p_ramp_limit_up_run_big_m:
     description: >-
@@ -146,11 +158,7 @@ constraints:
       raises internal power no faster than its limit of the chosen build; the big M
       releases the row in the snapshot it turns on
     dims: [scenario, snapshot, process]
-    where: >-
-      Process_committable AND Process_p_nom_extendable AND NOT (Process_p_nom_mod > 0)
-      AND (Process_ramp_limit_up OR Process_ramp_limit_start_up)
-      AND (position(snapshot, within=snapshot_period[period]) > 0 OR (position(snapshot) == 0 AND (Process_status_initial == 0 OR Process_p_init)))
-      AND Process_active
+    where: Process_com_ext AND (Process_ramp_limit_up OR Process_ramp_limit_start_up) AND Process_ramps_from_previous
     expression: >-
       Process_p - Process_previous_p <=
       Process_ramp_up_rate * Process_p_nom_ext
@@ -161,11 +169,7 @@ constraints:
       committed extendable process ramps no further than its start-up ramp of
       the chosen build; the big M releases the row everywhere else
     dims: [scenario, snapshot, process]
-    where: >-
-      Process_committable AND Process_p_nom_extendable AND NOT (Process_p_nom_mod > 0)
-      AND (Process_ramp_limit_up OR Process_ramp_limit_start_up)
-      AND (position(snapshot, within=snapshot_period[period]) > 0 OR (position(snapshot) == 0 AND (Process_status_initial == 0 OR Process_p_init)))
-      AND Process_active
+    where: Process_com_ext AND (Process_ramp_limit_up OR Process_ramp_limit_start_up) AND Process_ramps_from_previous
     expression: >-
       Process_p - Process_previous_p <=
       Process_start_up_rate * Process_p_nom_ext
@@ -177,10 +181,9 @@ constraints:
       releases the row in the snapshot it turns off
     dims: [scenario, snapshot, process]
     where: >-
-      Process_committable AND Process_p_nom_extendable AND NOT (Process_p_nom_mod > 0)
+      Process_com_ext
       AND (Process_ramp_limit_down OR Process_ramp_limit_shut_down)
-      AND (position(snapshot, within=snapshot_period[period]) > 0 OR (position(snapshot) == 0 AND (Process_status_initial == 0 OR Process_p_init)))
-      AND Process_active
+      AND Process_ramps_from_previous
     expression: >-
       Process_previous_p - Process_p <=
       Process_ramp_down_rate * Process_p_nom_ext
@@ -192,10 +195,9 @@ constraints:
       the chosen build; the big M releases the row everywhere else
     dims: [scenario, snapshot, process]
     where: >-
-      Process_committable AND Process_p_nom_extendable AND NOT (Process_p_nom_mod > 0)
+      Process_com_ext
       AND (Process_ramp_limit_down OR Process_ramp_limit_shut_down)
-      AND (position(snapshot, within=snapshot_period[period]) > 0 OR (position(snapshot) == 0 AND (Process_status_initial == 0 OR Process_p_init)))
-      AND Process_active
+      AND Process_ramps_from_previous
     expression: >-
       Process_previous_p - Process_p <=
       Process_shut_down_rate * Process_p_nom_ext
@@ -212,7 +214,7 @@ constraints:
     where: >-
       (Process_ramp_limit_up OR Process_ramp_limit_start_up)
       AND NOT (Process_committable AND Process_p_nom_extendable AND NOT (Process_p_nom_mod > 0))
-      AND (position(snapshot, within=snapshot_period[period]) > 0 OR (position(snapshot) == 0 AND (Process_status_initial == 0 OR Process_p_init)))
+      AND Process_ramps_from_previous
       AND Process_active
     expression: Process_p - Process_previous_p <= Process_ramp_up_allowance
   Process_p_ramp_limit_down:
@@ -227,7 +229,7 @@ constraints:
     where: >-
       (Process_ramp_limit_down OR Process_ramp_limit_shut_down)
       AND NOT (Process_committable AND Process_p_nom_extendable AND NOT (Process_p_nom_mod > 0))
-      AND (position(snapshot, within=snapshot_period[period]) > 0 OR (position(snapshot) == 0 AND (Process_status_initial == 0 OR Process_p_init)))
+      AND Process_ramps_from_previous
       AND Process_active
     expression: Process_previous_p - Process_p <= Process_ramp_down_allowance
 
@@ -285,6 +287,7 @@ assumptions:
 | $`\widetilde{\mathrm{z}}^{\mathrm{nom}}`$ | `Process_p_nom_effective` over $`\Xi \times \mathcal{J}`$, an expression another file defines |
 | $`\overleftarrow{u}^{z}`$ | `Process_previous_status` over $`\Xi \times \mathcal{T} \times \mathcal{J}`$, an expression another file defines |
 | $`\widehat{\mathrm{z}}^{\mathrm{nom}}`$ | `Process_p_nom_committed` over $`\Xi \times \mathcal{J}`$, an expression another file defines |
+| $`\mathrm{on}^{z,\mathrm{com,ext}}`$ | `Process_com_ext` over $`\mathcal{T} \times \mathcal{J}`$, a mask another file defines |
 
 #### Definitions
 
@@ -298,6 +301,12 @@ assumptions:
 | $`\Delta^{z,+}`$ | `Process_ramp_up_allowance` over $`\Xi \times \mathcal{T} \times \mathcal{J}`$ — how far a process may raise internal power between two snapshots — its ramp limit of the build while it stays on, plus its start-up ramp in the snapshot it turns on |
 | $`\Delta^{z,-}`$ | `Process_ramp_down_allowance` over $`\Xi \times \mathcal{T} \times \mathcal{J}`$ — how far a process may lower internal power between two snapshots — its ramp limit of the build while it stays on, plus its shut-down ramp in the snapshot it turns off |
 
+#### Masks
+
+| Symbol | Meaning |
+|---|---|
+| $`\mathrm{prev}^{z}`$ | `Process_ramps_from_previous` over $`\Xi \times \mathcal{T} \times \mathcal{J}`$ — a snapshot whose ramp reads a previous output — any snapshot but its period's first, and the horizon's first where the process comes in off or carries an initial output |
+
 $`\mathrm{pos}(t)`$ denotes where index $`t`$ sits along its dimension's own order — the order `shift` steps along, not the order labels sort in — counted from $`0`$. The index itself stays the coordinate, so $`t`$ compares against labels and $`\mathrm{pos}(t)`$ against positions.
 
 $`\mathrm{pos}_{\mathrm{relation}(t)}(t)`$ counts within the group a relation puts $`t`$ in: the subscript names the map, $`\mathcal{T}_{\mathrm{relation}(t)}`$ is the group it lands in, and that group has a first position of its own.
@@ -307,37 +316,37 @@ $`\mathrm{pos}_{\mathrm{relation}(t)}(t)`$ counts within the group a relation pu
 **`Process_p_ramp_limit_up_run_big_m`**
 
 ```math
-z_{\xi,t,j} - \overleftarrow{z}_{\xi,t,j} \le \widetilde{\mathrm{ru}}^{z}_{\xi,t,j} \cdot Z_{j} + \mathrm{M}^{z}_{\xi,j} - \mathrm{M}^{z}_{\xi,j} \cdot \overleftarrow{u}^{z}_{\xi,t,j} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{com}^{z}_{j} \wedge \mathrm{ext}^{z}_{j} \wedge \neg \left( \mathrm{z}^{\mathrm{mod}}_{j} > 0 \right) \wedge \left( \mathrm{ru}^{z}_{\xi,t,j} \text{ is defined} \vee \mathrm{ru}^{z,\mathrm{up}}_{\xi,j} \text{ is defined} \right) \wedge \left( \mathrm{pos}_{\mathrm{snapshot\_period}(t)}(t) > 0 \vee \mathrm{pos}(t) = 0 \wedge \left( \mathrm{u}^{z,0}_{\xi,j} = 0 \vee \mathrm{z}^{0}_{\xi,j} \text{ is defined} \right) \right) \wedge \mathrm{on}^{z}_{t,j}
+z_{\xi,t,j} - \overleftarrow{z}_{\xi,t,j} \le \widetilde{\mathrm{ru}}^{z}_{\xi,t,j} \cdot Z_{j} + \mathrm{M}^{z}_{\xi,j} - \mathrm{M}^{z}_{\xi,j} \cdot \overleftarrow{u}^{z}_{\xi,t,j} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{on}^{z,\mathrm{com,ext}}_{t,j} \wedge \left( \mathrm{ru}^{z}_{\xi,t,j} \text{ is defined} \vee \mathrm{ru}^{z,\mathrm{up}}_{\xi,j} \text{ is defined} \right) \wedge \mathrm{prev}^{z}_{\xi,t,j}
 ```
 
 **`Process_p_ramp_limit_up_start_big_m`**
 
 ```math
-z_{\xi,t,j} - \overleftarrow{z}_{\xi,t,j} \le \widetilde{\mathrm{ru}}^{z,\mathrm{up}}_{\xi,j} \cdot Z_{j} + \mathrm{M}^{z}_{\xi,j} - \mathrm{M}^{z}_{\xi,j} \cdot \mathit{up}^{z}_{\xi,t,j} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{com}^{z}_{j} \wedge \mathrm{ext}^{z}_{j} \wedge \neg \left( \mathrm{z}^{\mathrm{mod}}_{j} > 0 \right) \wedge \left( \mathrm{ru}^{z}_{\xi,t,j} \text{ is defined} \vee \mathrm{ru}^{z,\mathrm{up}}_{\xi,j} \text{ is defined} \right) \wedge \left( \mathrm{pos}_{\mathrm{snapshot\_period}(t)}(t) > 0 \vee \mathrm{pos}(t) = 0 \wedge \left( \mathrm{u}^{z,0}_{\xi,j} = 0 \vee \mathrm{z}^{0}_{\xi,j} \text{ is defined} \right) \right) \wedge \mathrm{on}^{z}_{t,j}
+z_{\xi,t,j} - \overleftarrow{z}_{\xi,t,j} \le \widetilde{\mathrm{ru}}^{z,\mathrm{up}}_{\xi,j} \cdot Z_{j} + \mathrm{M}^{z}_{\xi,j} - \mathrm{M}^{z}_{\xi,j} \cdot \mathit{up}^{z}_{\xi,t,j} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{on}^{z,\mathrm{com,ext}}_{t,j} \wedge \left( \mathrm{ru}^{z}_{\xi,t,j} \text{ is defined} \vee \mathrm{ru}^{z,\mathrm{up}}_{\xi,j} \text{ is defined} \right) \wedge \mathrm{prev}^{z}_{\xi,t,j}
 ```
 
 **`Process_p_ramp_limit_down_run_big_m`**
 
 ```math
-\overleftarrow{z}_{\xi,t,j} - z_{\xi,t,j} \le \widetilde{\mathrm{rd}}^{z}_{\xi,t,j} \cdot Z_{j} + \mathrm{M}^{z}_{\xi,j} - \mathrm{M}^{z}_{\xi,j} \cdot u^{z}_{\xi,t,j} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{com}^{z}_{j} \wedge \mathrm{ext}^{z}_{j} \wedge \neg \left( \mathrm{z}^{\mathrm{mod}}_{j} > 0 \right) \wedge \left( \mathrm{rd}^{z}_{\xi,t,j} \text{ is defined} \vee \mathrm{rd}^{z,\mathrm{dn}}_{\xi,j} \text{ is defined} \right) \wedge \left( \mathrm{pos}_{\mathrm{snapshot\_period}(t)}(t) > 0 \vee \mathrm{pos}(t) = 0 \wedge \left( \mathrm{u}^{z,0}_{\xi,j} = 0 \vee \mathrm{z}^{0}_{\xi,j} \text{ is defined} \right) \right) \wedge \mathrm{on}^{z}_{t,j}
+\overleftarrow{z}_{\xi,t,j} - z_{\xi,t,j} \le \widetilde{\mathrm{rd}}^{z}_{\xi,t,j} \cdot Z_{j} + \mathrm{M}^{z}_{\xi,j} - \mathrm{M}^{z}_{\xi,j} \cdot u^{z}_{\xi,t,j} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{on}^{z,\mathrm{com,ext}}_{t,j} \wedge \left( \mathrm{rd}^{z}_{\xi,t,j} \text{ is defined} \vee \mathrm{rd}^{z,\mathrm{dn}}_{\xi,j} \text{ is defined} \right) \wedge \mathrm{prev}^{z}_{\xi,t,j}
 ```
 
 **`Process_p_ramp_limit_down_shut_big_m`**
 
 ```math
-\overleftarrow{z}_{\xi,t,j} - z_{\xi,t,j} \le \widetilde{\mathrm{rd}}^{z,\mathrm{dn}}_{\xi,j} \cdot Z_{j} + \mathrm{M}^{z}_{\xi,j} - \mathrm{M}^{z}_{\xi,j} \cdot \mathit{dn}^{z}_{\xi,t,j} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{com}^{z}_{j} \wedge \mathrm{ext}^{z}_{j} \wedge \neg \left( \mathrm{z}^{\mathrm{mod}}_{j} > 0 \right) \wedge \left( \mathrm{rd}^{z}_{\xi,t,j} \text{ is defined} \vee \mathrm{rd}^{z,\mathrm{dn}}_{\xi,j} \text{ is defined} \right) \wedge \left( \mathrm{pos}_{\mathrm{snapshot\_period}(t)}(t) > 0 \vee \mathrm{pos}(t) = 0 \wedge \left( \mathrm{u}^{z,0}_{\xi,j} = 0 \vee \mathrm{z}^{0}_{\xi,j} \text{ is defined} \right) \right) \wedge \mathrm{on}^{z}_{t,j}
+\overleftarrow{z}_{\xi,t,j} - z_{\xi,t,j} \le \widetilde{\mathrm{rd}}^{z,\mathrm{dn}}_{\xi,j} \cdot Z_{j} + \mathrm{M}^{z}_{\xi,j} - \mathrm{M}^{z}_{\xi,j} \cdot \mathit{dn}^{z}_{\xi,t,j} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{on}^{z,\mathrm{com,ext}}_{t,j} \wedge \left( \mathrm{rd}^{z}_{\xi,t,j} \text{ is defined} \vee \mathrm{rd}^{z,\mathrm{dn}}_{\xi,j} \text{ is defined} \right) \wedge \mathrm{prev}^{z}_{\xi,t,j}
 ```
 
 **`Process_p_ramp_limit_up`**
 
 ```math
-z_{\xi,t,j} - \overleftarrow{z}_{\xi,t,j} \le \Delta^{z,+}_{\xi,t,j} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \left( \mathrm{ru}^{z}_{\xi,t,j} \text{ is defined} \vee \mathrm{ru}^{z,\mathrm{up}}_{\xi,j} \text{ is defined} \right) \wedge \neg \left( \mathrm{com}^{z}_{j} \wedge \mathrm{ext}^{z}_{j} \wedge \neg \left( \mathrm{z}^{\mathrm{mod}}_{j} > 0 \right) \right) \wedge \left( \mathrm{pos}_{\mathrm{snapshot\_period}(t)}(t) > 0 \vee \mathrm{pos}(t) = 0 \wedge \left( \mathrm{u}^{z,0}_{\xi,j} = 0 \vee \mathrm{z}^{0}_{\xi,j} \text{ is defined} \right) \right) \wedge \mathrm{on}^{z}_{t,j}
+z_{\xi,t,j} - \overleftarrow{z}_{\xi,t,j} \le \Delta^{z,+}_{\xi,t,j} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \left( \mathrm{ru}^{z}_{\xi,t,j} \text{ is defined} \vee \mathrm{ru}^{z,\mathrm{up}}_{\xi,j} \text{ is defined} \right) \wedge \neg \left( \mathrm{com}^{z}_{j} \wedge \mathrm{ext}^{z}_{j} \wedge \neg \left( \mathrm{z}^{\mathrm{mod}}_{j} > 0 \right) \right) \wedge \mathrm{prev}^{z}_{\xi,t,j} \wedge \mathrm{on}^{z}_{t,j}
 ```
 
 **`Process_p_ramp_limit_down`**
 
 ```math
-\overleftarrow{z}_{\xi,t,j} - z_{\xi,t,j} \le \Delta^{z,-}_{\xi,t,j} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \left( \mathrm{rd}^{z}_{\xi,t,j} \text{ is defined} \vee \mathrm{rd}^{z,\mathrm{dn}}_{\xi,j} \text{ is defined} \right) \wedge \neg \left( \mathrm{com}^{z}_{j} \wedge \mathrm{ext}^{z}_{j} \wedge \neg \left( \mathrm{z}^{\mathrm{mod}}_{j} > 0 \right) \right) \wedge \left( \mathrm{pos}_{\mathrm{snapshot\_period}(t)}(t) > 0 \vee \mathrm{pos}(t) = 0 \wedge \left( \mathrm{u}^{z,0}_{\xi,j} = 0 \vee \mathrm{z}^{0}_{\xi,j} \text{ is defined} \right) \right) \wedge \mathrm{on}^{z}_{t,j}
+\overleftarrow{z}_{\xi,t,j} - z_{\xi,t,j} \le \Delta^{z,-}_{\xi,t,j} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \left( \mathrm{rd}^{z}_{\xi,t,j} \text{ is defined} \vee \mathrm{rd}^{z,\mathrm{dn}}_{\xi,j} \text{ is defined} \right) \wedge \neg \left( \mathrm{com}^{z}_{j} \wedge \mathrm{ext}^{z}_{j} \wedge \neg \left( \mathrm{z}^{\mathrm{mod}}_{j} > 0 \right) \right) \wedge \mathrm{prev}^{z}_{\xi,t,j} \wedge \mathrm{on}^{z}_{t,j}
 ```
 
 #### Definitions
@@ -384,6 +393,14 @@ z_{\xi,t,j} - \overleftarrow{z}_{\xi,t,j} \le \Delta^{z,+}_{\xi,t,j} \qquad \for
 \Delta^{z,-}_{\xi,t,j} = \begin{cases} \widetilde{\mathrm{rd}}^{z}_{\xi,t,j} \cdot \widehat{\mathrm{z}}^{\mathrm{nom}}_{\xi,j} \cdot u^{z}_{\xi,t,j} + \widetilde{\mathrm{rd}}^{z,\mathrm{dn}}_{\xi,j} \cdot \widehat{\mathrm{z}}^{\mathrm{nom}}_{\xi,j} \cdot \left( \overleftarrow{u}^{z}_{\xi,t,j} - u^{z}_{\xi,t,j} \right) & \text{if } \mathrm{com}^{z}_{j} \\ \widetilde{\mathrm{rd}}^{z}_{\xi,t,j} \cdot \widetilde{\mathrm{z}}^{\mathrm{nom}}_{\xi,j} & \text{otherwise} \end{cases} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J}
 ```
 
+#### Masks
+
+**`Process_ramps_from_previous`**
+
+```math
+\mathrm{prev}^{z}_{\xi,t,j} \iff \mathrm{pos}_{\mathrm{snapshot\_period}(t)}(t) > 0 \vee \mathrm{pos}(t) = 0 \wedge \left( \mathrm{u}^{z,0}_{\xi,j} = 0 \vee \mathrm{z}^{0}_{\xi,j} \text{ is defined} \right) \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J}
+```
+
 #### Assumptions
 
 **`Process_came_in_running_unless_committable`**
diff --git a/docs/examples/pypsa/storage_unit.md b/docs/examples/pypsa/storage_unit.md
index ca5e9944..ee22aaab 100644
--- a/docs/examples/pypsa/storage_unit.md
+++ b/docs/examples/pypsa/storage_unit.md
@@ -323,70 +323,82 @@ expressions:
       sum(StorageUnit_sign * (StorageUnit_p_dispatch - StorageUnit_p_store), over=storage_unit, by=StorageUnit_bus[bus])
     adds_to: Bus_injection
 
+masks:
+  StorageUnit_fix:
+    description: >-
+      a storage unit with a fixed build that stands in the snapshot's period —
+      PyPSA's `fix` rows
+    where: NOT StorageUnit_p_nom_extendable AND StorageUnit_active
+  StorageUnit_ext:
+    description: >-
+      a storage unit with an extendable build that stands in the snapshot's
+      period — PyPSA's `ext` rows
+    where: StorageUnit_p_nom_extendable AND StorageUnit_active
+
 constraints:
   StorageUnit_fix_p_dispatch_lower:
     description: "`StorageUnit-fix-p_dispatch-lower` — dispatch is non-negative"
     dims: [scenario, snapshot, storage_unit]
-    where: not StorageUnit_p_nom_extendable AND StorageUnit_active
+    where: StorageUnit_fix
     expression: StorageUnit_p_dispatch >= 0
   StorageUnit_fix_p_dispatch_upper:
     description: "`StorageUnit-fix-p_dispatch-upper` — a fixed unit dispatches at most its nominal power"
     dims: [scenario, snapshot, storage_unit]
-    where: not StorageUnit_p_nom_extendable AND StorageUnit_active
+    where: StorageUnit_fix
     expression: StorageUnit_p_dispatch <= StorageUnit_p_max_pu * StorageUnit_p_nom
   StorageUnit_fix_p_store_lower:
     description: "`StorageUnit-fix-p_store-lower` — storing is non-negative"
     dims: [scenario, snapshot, storage_unit]
-    where: not StorageUnit_p_nom_extendable AND StorageUnit_active
+    where: StorageUnit_fix
     expression: StorageUnit_p_store >= 0
   StorageUnit_fix_p_store_upper:
     description: >-
       `StorageUnit-fix-p_store-upper` — a fixed unit stores at most its
       nominal power, the minimum-per-unit column carrying that cap negated
     dims: [scenario, snapshot, storage_unit]
-    where: not StorageUnit_p_nom_extendable AND StorageUnit_active
+    where: StorageUnit_fix
     expression: StorageUnit_p_store <= -StorageUnit_p_min_pu * StorageUnit_p_nom
   StorageUnit_fix_state_of_charge_lower:
     description: "`StorageUnit-fix-state_of_charge-lower` — charge is non-negative"
     dims: [scenario, snapshot, storage_unit]
-    where: not StorageUnit_p_nom_extendable AND StorageUnit_active
+    where: StorageUnit_fix
     expression: StorageUnit_state_of_charge >= 0
   StorageUnit_fix_state_of_charge_upper:
     description: "`StorageUnit-fix-state_of_charge-upper` — a fixed unit holds at most its hours at nominal power"
     dims: [scenario, snapshot, storage_unit]
-    where: not StorageUnit_p_nom_extendable AND StorageUnit_active
+    where: StorageUnit_fix
     expression: StorageUnit_state_of_charge <= StorageUnit_max_hours * StorageUnit_p_nom
   StorageUnit_ext_p_dispatch_lower:
     description: "`StorageUnit-ext-p_dispatch-lower` — dispatch is non-negative"
     dims: [scenario, snapshot, storage_unit]
-    where: StorageUnit_p_nom_extendable AND StorageUnit_active
+    where: StorageUnit_ext
     expression: StorageUnit_p_dispatch >= 0
   StorageUnit_ext_p_dispatch_upper:
     description: "`StorageUnit-ext-p_dispatch-upper` — an extendable unit dispatches at most the chosen build"
     dims: [scenario, snapshot, storage_unit]
-    where: StorageUnit_p_nom_extendable AND StorageUnit_active
+    where: StorageUnit_ext
     expression: StorageUnit_p_dispatch <= StorageUnit_p_max_pu * StorageUnit_p_nom_ext
   StorageUnit_ext_p_store_lower:
     description: "`StorageUnit-ext-p_store-lower` — storing is non-negative"
     dims: [scenario, snapshot, storage_unit]
-    where: StorageUnit_p_nom_extendable AND StorageUnit_active
+    where: StorageUnit_ext
     expression: StorageUnit_p_store >= 0
   StorageUnit_ext_p_store_upper:
     description: >-
       `StorageUnit-ext-p_store-upper` — an extendable unit stores at most the
       chosen build, the minimum-per-unit column carrying that cap negated
     dims: [scenario, snapshot, storage_unit]
-    where: StorageUnit_p_nom_extendable AND StorageUnit_active
+    where: StorageUnit_ext
     expression: StorageUnit_p_store <= -StorageUnit_p_min_pu * StorageUnit_p_nom_ext
   StorageUnit_ext_state_of_charge_lower:
     description: "`StorageUnit-ext-state_of_charge-lower` — charge is non-negative"
     dims: [scenario, snapshot, storage_unit]
-    where: StorageUnit_p_nom_extendable AND StorageUnit_active
+    where: StorageUnit_ext
     expression: StorageUnit_state_of_charge >= 0
   StorageUnit_ext_state_of_charge_upper:
     description: "`StorageUnit-ext-state_of_charge-upper` — an extendable unit holds at most its hours at the chosen build"
     dims: [scenario, snapshot, storage_unit]
-    where: StorageUnit_p_nom_extendable AND StorageUnit_active
+    where: StorageUnit_ext
     expression: StorageUnit_state_of_charge <= StorageUnit_max_hours * StorageUnit_p_nom_ext
   StorageUnit_ext_p_nom_lower:
     description: "`StorageUnit-ext-p_nom-lower` — the chosen build is at least its floor in every scenario"
@@ -591,6 +603,13 @@ assumptions:
 | $`\mathit{StorageUnit\_additions}`$ | `StorageUnit_additions` over $`\mathcal{Y} \times \mathcal{I}`$ |
 | $`\mathit{StorageUnit\_injection}`$ | `StorageUnit_injection` over $`\Xi \times \mathcal{T} \times \mathcal{N}`$ |
 
+#### Masks
+
+| Symbol | Meaning |
+|---|---|
+| $`\mathrm{on}^{h,\mathrm{fix}}`$ | `StorageUnit_fix` over $`\mathcal{T} \times \mathcal{S}`$ — a storage unit with a fixed build that stands in the snapshot's period — PyPSA's `fix` rows |
+| $`\mathrm{on}^{h,\mathrm{ext}}`$ | `StorageUnit_ext` over $`\mathcal{T} \times \mathcal{S}`$ — a storage unit with an extendable build that stands in the snapshot's period — PyPSA's `ext` rows |
+
 $`t \ominus k`$ denotes cyclic translation: index $`t-k`$ taken modulo the size of the dimension (`roll`). Plain $`t-k`$ (`shift`) has no wraparound — terms translated past the edge are simply absent.
 
 $`t \ominus^{\mathrm{relation}(t)} k`$ denotes a translation counted inside the group a relation puts $`t`$ in (`shift(within=relation[c])`), so a term never crosses out of its own group.
@@ -606,73 +625,73 @@ $`\lvert \mathcal{T} \rvert`$ denotes the size of the set being counted along, a
 **`StorageUnit_fix_p_dispatch_lower`**
 
 ```math
-h^{+}_{\xi,t,s} \ge 0 \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ s \in \mathcal{S} \,:\, \neg \mathrm{ext}^{h}_{s} \wedge \mathrm{on}^{h}_{t,s}
+h^{+}_{\xi,t,s} \ge 0 \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ s \in \mathcal{S} \,:\, \mathrm{on}^{h,\mathrm{fix}}_{t,s}
 ```
 
 **`StorageUnit_fix_p_dispatch_upper`**
 
 ```math
-h^{+}_{\xi,t,s} \le \overline{\mathrm{h}}_{\xi,t,s} \cdot \mathrm{h}^{\mathrm{nom}}_{\xi,s} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ s \in \mathcal{S} \,:\, \neg \mathrm{ext}^{h}_{s} \wedge \mathrm{on}^{h}_{t,s}
+h^{+}_{\xi,t,s} \le \overline{\mathrm{h}}_{\xi,t,s} \cdot \mathrm{h}^{\mathrm{nom}}_{\xi,s} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ s \in \mathcal{S} \,:\, \mathrm{on}^{h,\mathrm{fix}}_{t,s}
 ```
 
 **`StorageUnit_fix_p_store_lower`**
 
 ```math
-h^{-}_{\xi,t,s} \ge 0 \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ s \in \mathcal{S} \,:\, \neg \mathrm{ext}^{h}_{s} \wedge \mathrm{on}^{h}_{t,s}
+h^{-}_{\xi,t,s} \ge 0 \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ s \in \mathcal{S} \,:\, \mathrm{on}^{h,\mathrm{fix}}_{t,s}
 ```
 
 **`StorageUnit_fix_p_store_upper`**
 
 ```math
-h^{-}_{\xi,t,s} \le -\underline{\mathrm{h}}_{\xi,t,s} \cdot \mathrm{h}^{\mathrm{nom}}_{\xi,s} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ s \in \mathcal{S} \,:\, \neg \mathrm{ext}^{h}_{s} \wedge \mathrm{on}^{h}_{t,s}
+h^{-}_{\xi,t,s} \le -\underline{\mathrm{h}}_{\xi,t,s} \cdot \mathrm{h}^{\mathrm{nom}}_{\xi,s} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ s \in \mathcal{S} \,:\, \mathrm{on}^{h,\mathrm{fix}}_{t,s}
 ```
 
 **`StorageUnit_fix_state_of_charge_lower`**
 
 ```math
-\mathit{soc}_{\xi,t,s} \ge 0 \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ s \in \mathcal{S} \,:\, \neg \mathrm{ext}^{h}_{s} \wedge \mathrm{on}^{h}_{t,s}
+\mathit{soc}_{\xi,t,s} \ge 0 \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ s \in \mathcal{S} \,:\, \mathrm{on}^{h,\mathrm{fix}}_{t,s}
 ```
 
 **`StorageUnit_fix_state_of_charge_upper`**
 
 ```math
-\mathit{soc}_{\xi,t,s} \le \mathrm{T}^{h}_{\xi,s} \cdot \mathrm{h}^{\mathrm{nom}}_{\xi,s} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ s \in \mathcal{S} \,:\, \neg \mathrm{ext}^{h}_{s} \wedge \mathrm{on}^{h}_{t,s}
+\mathit{soc}_{\xi,t,s} \le \mathrm{T}^{h}_{\xi,s} \cdot \mathrm{h}^{\mathrm{nom}}_{\xi,s} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ s \in \mathcal{S} \,:\, \mathrm{on}^{h,\mathrm{fix}}_{t,s}
 ```
 
 **`StorageUnit_ext_p_dispatch_lower`**
 
 ```math
-h^{+}_{\xi,t,s} \ge 0 \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ s \in \mathcal{S} \,:\, \mathrm{ext}^{h}_{s} \wedge \mathrm{on}^{h}_{t,s}
+h^{+}_{\xi,t,s} \ge 0 \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ s \in \mathcal{S} \,:\, \mathrm{on}^{h,\mathrm{ext}}_{t,s}
 ```
 
 **`StorageUnit_ext_p_dispatch_upper`**
 
 ```math
-h^{+}_{\xi,t,s} \le \overline{\mathrm{h}}_{\xi,t,s} \cdot H_{s} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ s \in \mathcal{S} \,:\, \mathrm{ext}^{h}_{s} \wedge \mathrm{on}^{h}_{t,s}
+h^{+}_{\xi,t,s} \le \overline{\mathrm{h}}_{\xi,t,s} \cdot H_{s} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ s \in \mathcal{S} \,:\, \mathrm{on}^{h,\mathrm{ext}}_{t,s}
 ```
 
 **`StorageUnit_ext_p_store_lower`**
 
 ```math
-h^{-}_{\xi,t,s} \ge 0 \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ s \in \mathcal{S} \,:\, \mathrm{ext}^{h}_{s} \wedge \mathrm{on}^{h}_{t,s}
+h^{-}_{\xi,t,s} \ge 0 \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ s \in \mathcal{S} \,:\, \mathrm{on}^{h,\mathrm{ext}}_{t,s}
 ```
 
 **`StorageUnit_ext_p_store_upper`**
 
 ```math
-h^{-}_{\xi,t,s} \le -\underline{\mathrm{h}}_{\xi,t,s} \cdot H_{s} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ s \in \mathcal{S} \,:\, \mathrm{ext}^{h}_{s} \wedge \mathrm{on}^{h}_{t,s}
+h^{-}_{\xi,t,s} \le -\underline{\mathrm{h}}_{\xi,t,s} \cdot H_{s} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ s \in \mathcal{S} \,:\, \mathrm{on}^{h,\mathrm{ext}}_{t,s}
 ```
 
 **`StorageUnit_ext_state_of_charge_lower`**
 
 ```math
-\mathit{soc}_{\xi,t,s} \ge 0 \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ s \in \mathcal{S} \,:\, \mathrm{ext}^{h}_{s} \wedge \mathrm{on}^{h}_{t,s}
+\mathit{soc}_{\xi,t,s} \ge 0 \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ s \in \mathcal{S} \,:\, \mathrm{on}^{h,\mathrm{ext}}_{t,s}
 ```
 
 **`StorageUnit_ext_state_of_charge_upper`**
 
 ```math
-\mathit{soc}_{\xi,t,s} \le \mathrm{T}^{h}_{\xi,s} \cdot H_{s} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ s \in \mathcal{S} \,:\, \mathrm{ext}^{h}_{s} \wedge \mathrm{on}^{h}_{t,s}
+\mathit{soc}_{\xi,t,s} \le \mathrm{T}^{h}_{\xi,s} \cdot H_{s} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ s \in \mathcal{S} \,:\, \mathrm{on}^{h,\mathrm{ext}}_{t,s}
 ```
 
 **`StorageUnit_ext_p_nom_lower`**
@@ -785,6 +804,20 @@ h^{-}_{\xi,t,s} = \mathrm{h}^{-,\mathrm{set}}_{\xi,t,s} \qquad \forall\, \xi \in
 \mathit{StorageUnit\_injection}_{\xi,t,n} = \sum_{s \in \mathcal{S} \,:\, \mathrm{StorageUnit\_bus}(s) = n} \mathrm{sgn}^{h}_{s} \cdot \left( h^{+}_{\xi,t,s} - h^{-}_{\xi,t,s} \right) \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ n \in \mathcal{N}
 ```
 
+#### Masks
+
+**`StorageUnit_fix`**
+
+```math
+\mathrm{on}^{h,\mathrm{fix}}_{t,s} \iff \neg \mathrm{ext}^{h}_{s} \wedge \mathrm{on}^{h}_{t,s} \qquad \forall\, t \in \mathcal{T},\ s \in \mathcal{S}
+```
+
+**`StorageUnit_ext`**
+
+```math
+\mathrm{on}^{h,\mathrm{ext}}_{t,s} \iff \mathrm{ext}^{h}_{s} \wedge \mathrm{on}^{h}_{t,s} \qquad \forall\, t \in \mathcal{T},\ s \in \mathcal{S}
+```
+
 #### Variable domains
 
 **`StorageUnit_p_dispatch`**
diff --git a/docs/examples/pypsa/transformer.md b/docs/examples/pypsa/transformer.md
index a74e06dd..53ae70f0 100644
--- a/docs/examples/pypsa/transformer.md
+++ b/docs/examples/pypsa/transformer.md
@@ -183,7 +183,7 @@ variables:
       a line does; absent, and zero in the balance, where the network is
       lossless
     dims: [scenario, snapshot, transformer]
-    where: transmission_losses AND Transformer_active
+    where: Transformer_lossy
     absence: zero
     bounds:
       lower: 0
@@ -246,6 +246,13 @@ expressions:
       + sum(Transformer_phase_shift * at(Transformer_phase_shift_cycle_weight, by=snapshot_period[period]), over=transformer)
     adds_to: Cycle_angle_sum
 
+masks:
+  Transformer_lossy:
+    description: >-
+      a transformer that stands in the snapshot's period, where the run models
+      transmission losses
+    where: transmission_losses AND Transformer_active
+
 constraints:
   Transformer_fix_s_lower:
     description: "`Transformer-fix-s-lower` — a fixed transformer carries at least the negative of its rating, the loss counted against it"
@@ -327,7 +334,7 @@ constraints:
   Transformer_loss_upper:
     description: "`Transformer-loss_upper` — a transformer dissipates at most the loss at its rating"
     dims: [scenario, snapshot, transformer]
-    where: transmission_losses AND Transformer_active
+    where: Transformer_lossy
     expression: Transformer_loss <= Transformer_loss_max
   Transformer_loss_tangents_forward:
     description: >-
@@ -335,14 +342,14 @@ constraints:
       loss sits above every cut to its curve for flow one way, as a line's
       does, over the segment dimension
     dims: [scenario, snapshot, transformer, segment]
-    where: transmission_losses AND Transformer_active
+    where: Transformer_lossy
     expression: Transformer_loss + Transformer_loss_slope * Transformer_s >= Transformer_loss_offset
   Transformer_loss_tangents_reverse:
     description: >-
       `Transformer-loss_tangents-{k}--1`, `Transformer-loss_secants-neg` — the
       same fan mirrored, the loss depending on the flow's magnitude
     dims: [scenario, snapshot, transformer, segment]
-    where: transmission_losses AND Transformer_active
+    where: Transformer_lossy
     expression: Transformer_loss - Transformer_loss_slope * Transformer_s >= Transformer_loss_offset
 ```
 
@@ -415,6 +422,12 @@ constraints:
 | $`\mathit{Transformer\_injection}`$ | `Transformer_injection` over $`\Xi \times \mathcal{T} \times \mathcal{N}`$ |
 | $`\mathit{Transformer\_angle\_sum}`$ | `Transformer_angle_sum` over $`\Xi \times \mathcal{T} \times \mathcal{C}`$ |
 
+#### Masks
+
+| Symbol | Meaning |
+|---|---|
+| $`\mathrm{on}^{\sigma,\mathrm{lossy}}`$ | `Transformer_lossy` over $`\mathcal{T} \times \mathcal{M}`$ — a transformer that stands in the snapshot's period, where the run models transmission losses |
+
 Upright is what the data supplies — a parameter such as $`\mathrm{Transformer\_phase\_shift\_varying}`$, a coordinate map, a label — and italic is what the solver chooses, such as $`\mathit{Transformer\_phase\_shift}`$. An index is italic too, being what a quantifier chooses, and a set is script.
 
 #### Subject to
@@ -500,19 +513,19 @@ Upright is what the data supplies — a parameter such as $`\mathrm{Transformer\
 **`Transformer_loss_upper`**
 
 ```math
-\ell^{\sigma}_{\xi,t,m} \le \overline{\ell}^{\sigma}_{\xi,t,m} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ m \in \mathcal{M} \,:\, \mathrm{lossy} \wedge \mathrm{on}^{\sigma}_{t,m}
+\ell^{\sigma}_{\xi,t,m} \le \overline{\ell}^{\sigma}_{\xi,t,m} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ m \in \mathcal{M} \,:\, \mathrm{on}^{\sigma,\mathrm{lossy}}_{t,m}
 ```
 
 **`Transformer_loss_tangents_forward`**
 
 ```math
-\ell^{\sigma}_{\xi,t,m} + \mathrm{a}^{\sigma}_{\xi,t,m,s} \cdot \sigma_{\xi,t,m} \ge \mathrm{b}^{\sigma}_{\xi,t,m,s} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ m \in \mathcal{M},\ s \in \mathcal{S} \,:\, \mathrm{lossy} \wedge \mathrm{on}^{\sigma}_{t,m}
+\ell^{\sigma}_{\xi,t,m} + \mathrm{a}^{\sigma}_{\xi,t,m,s} \cdot \sigma_{\xi,t,m} \ge \mathrm{b}^{\sigma}_{\xi,t,m,s} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ m \in \mathcal{M},\ s \in \mathcal{S} \,:\, \mathrm{on}^{\sigma,\mathrm{lossy}}_{t,m}
 ```
 
 **`Transformer_loss_tangents_reverse`**
 
 ```math
-\ell^{\sigma}_{\xi,t,m} - \mathrm{a}^{\sigma}_{\xi,t,m,s} \cdot \sigma_{\xi,t,m} \ge \mathrm{b}^{\sigma}_{\xi,t,m,s} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ m \in \mathcal{M},\ s \in \mathcal{S} \,:\, \mathrm{lossy} \wedge \mathrm{on}^{\sigma}_{t,m}
+\ell^{\sigma}_{\xi,t,m} - \mathrm{a}^{\sigma}_{\xi,t,m,s} \cdot \sigma_{\xi,t,m} \ge \mathrm{b}^{\sigma}_{\xi,t,m,s} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ m \in \mathcal{M},\ s \in \mathcal{S} \,:\, \mathrm{on}^{\sigma,\mathrm{lossy}}_{t,m}
 ```
 
 #### Definitions
@@ -541,6 +554,14 @@ Upright is what the data supplies — a parameter such as $`\mathrm{Transformer\
 \mathit{Transformer\_angle\_sum}_{\xi,t,c} = \sum_{m \in \mathcal{M}} \sigma_{\xi,t,m} \cdot \mathrm{x}^{\sigma}_{\mathrm{snapshot\_period}(t),m,c} + \sum_{m \in \mathcal{M}} \vartheta_{t,m,c} + \sum_{m \in \mathcal{M}} \mathit{Transformer\_phase\_shift}_{\xi,t,m} \cdot \mathrm{Transformer\_phase\_shift\_cycle\_weight}_{\mathrm{snapshot\_period}(t),m,c} \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ c \in \mathcal{C}
 ```
 
+#### Masks
+
+**`Transformer_lossy`**
+
+```math
+\mathrm{on}^{\sigma,\mathrm{lossy}}_{t,m} \iff \mathrm{lossy} \wedge \mathrm{on}^{\sigma}_{t,m} \qquad \forall\, t \in \mathcal{T},\ m \in \mathcal{M}
+```
+
 #### Variable domains
 
 **`Transformer_s`**
@@ -552,7 +573,7 @@ Upright is what the data supplies — a parameter such as $`\mathrm{Transformer\
 **`Transformer_loss`**
 
 ```math
-\ell^{\sigma}_{\xi,t,m} \ge 0 \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ m \in \mathcal{M} \,:\, \mathrm{lossy} \wedge \mathrm{on}^{\sigma}_{t,m}
+\ell^{\sigma}_{\xi,t,m} \ge 0 \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ m \in \mathcal{M} \,:\, \mathrm{on}^{\sigma,\mathrm{lossy}}_{t,m}
 ```
 
 **`Transformer_phase_shift`**
diff --git a/docs/examples/pypsa_linearized_uc.md b/docs/examples/pypsa_linearized_uc.md
index 2e8ba38f..e57606bf 100644
--- a/docs/examples/pypsa_linearized_uc.md
+++ b/docs/examples/pypsa_linearized_uc.md
@@ -463,7 +463,7 @@ Generator_status:
 ```
 
 ```math
-0 \le u_{\xi,t,g} \le 1 \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{com}_{g} \wedge \mathrm{on}_{t,g}
+0 \le u_{\xi,t,g} \le 1 \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{on}^{\mathrm{com}}_{t,g}
 ```
 
 ### `Generator-start_up`
@@ -479,7 +479,7 @@ Generator_start_up:
 ```
 
 ```math
-0 \le \mathit{up}_{\xi,t,g} \le 1 \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{com}_{g} \wedge \mathrm{on}_{t,g}
+0 \le \mathit{up}_{\xi,t,g} \le 1 \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{on}^{\mathrm{com}}_{t,g}
 ```
 
 ### `Generator-shut_down`
@@ -495,7 +495,7 @@ Generator_shut_down:
 ```
 
 ```math
-0 \le \mathit{dn}_{\xi,t,g} \le 1 \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{com}_{g} \wedge \mathrm{on}_{t,g}
+0 \le \mathit{dn}_{\xi,t,g} \le 1 \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{on}^{\mathrm{com}}_{t,g}
 ```
 
 ### `Link-status`
@@ -514,7 +514,7 @@ Link_status:
 ```
 
 ```math
-0 \le u^{f}_{\xi,t,l} \le 1 \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{com}^{f}_{l} \wedge \mathrm{on}^{f}_{t,l}
+0 \le u^{f}_{\xi,t,l} \le 1 \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{on}^{f,\mathrm{com}}_{t,l}
 ```
 
 ### `Link-start_up`
@@ -530,7 +530,7 @@ Link_start_up:
 ```
 
 ```math
-0 \le \mathit{up}^{f}_{\xi,t,l} \le 1 \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{com}^{f}_{l} \wedge \mathrm{on}^{f}_{t,l}
+0 \le \mathit{up}^{f}_{\xi,t,l} \le 1 \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{on}^{f,\mathrm{com}}_{t,l}
 ```
 
 ### `Link-shut_down`
@@ -546,7 +546,7 @@ Link_shut_down:
 ```
 
 ```math
-0 \le \mathit{dn}^{f}_{\xi,t,l} \le 1 \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{com}^{f}_{l} \wedge \mathrm{on}^{f}_{t,l}
+0 \le \mathit{dn}^{f}_{\xi,t,l} \le 1 \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ l \in \mathcal{L} \,:\, \mathrm{on}^{f,\mathrm{com}}_{t,l}
 ```
 
 ### `Process-status`
@@ -565,7 +565,7 @@ Process_status:
 ```
 
 ```math
-0 \le u^{z}_{\xi,t,j} \le 1 \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{com}^{z}_{j} \wedge \mathrm{on}^{z}_{t,j}
+0 \le u^{z}_{\xi,t,j} \le 1 \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{on}^{z,\mathrm{com}}_{t,j}
 ```
 
 ### `Process-start_up`
@@ -581,7 +581,7 @@ Process_start_up:
 ```
 
 ```math
-0 \le \mathit{up}^{z}_{\xi,t,j} \le 1 \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{com}^{z}_{j} \wedge \mathrm{on}^{z}_{t,j}
+0 \le \mathit{up}^{z}_{\xi,t,j} \le 1 \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{on}^{z,\mathrm{com}}_{t,j}
 ```
 
 ### `Process-shut_down`
@@ -597,7 +597,7 @@ Process_shut_down:
 ```
 
 ```math
-0 \le \mathit{dn}^{z}_{\xi,t,j} \le 1 \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{com}^{z}_{j} \wedge \mathrm{on}^{z}_{t,j}
+0 \le \mathit{dn}^{z}_{\xi,t,j} \le 1 \qquad \forall\, \xi \in \Xi,\ t \in \mathcal{T},\ j \in \mathcal{J} \,:\, \mathrm{on}^{z,\mathrm{com}}_{t,j}
 ```
 
 ### `Generator-com-p-before`
diff --git a/docs/howto/compose.md b/docs/howto/compose.md
index d1f2b50b..a6bcdf65 100644
--- a/docs/howto/compose.md
+++ b/docs/howto/compose.md
@@ -205,6 +205,7 @@ which each component pins at its own port.
 | any other declaration                             | one fragment declares it, and a second is refused                                                                                                                                                   |
 | an entry under `given:`                           | it is checked against the fragment that introduces the name, then folded into it. Its description fills the declaration where the introducer wrote none                                             |
 | a given expression                                | the definition's body carries no dimension the reader's `dims` do not name                                                                                                                          |
+| a given mask                                      | the reader's `dims` name the dimensions the defining fragment's predicate reads, no more and no fewer                                                                                               |
 | a given entry no fragment introduces              | it stays under `given:` until a host model provides it                                                                                                                                              |
 | an expression with `adds_to:`                     | the sum it names is the body one fragment defines, if any, followed by every term by its name, in the order of the list. [Terms](../reference/language/declarations.md#terms) gives what is refused |
 | `objective`                                       | one fragment sets it, and a second is refused. Several fragments contribute to it as terms of a sum the objective reads                                                                             |
diff --git a/docs/reference/language/declarations.md b/docs/reference/language/declarations.md
index 3595828b..7a14dfc7 100644
--- a/docs/reference/language/declarations.md
+++ b/docs/reference/language/declarations.md
@@ -89,8 +89,8 @@ A pinned variable is still a variable.
 
 `given:` holds what this file reads and does not build: data under
 `parameters:`, columns under `variables:`, named expressions under
-`expressions:`, and row families under `constraints:`. It takes those four keys
-and no other. A file with a `given:` block loads and prints on its own.
+`expressions:`, masks under `masks:`, and row families under `constraints:`. It
+takes those five keys and no other. A file with a `given:` block loads and prints on its own.
 
 ### `given: parameters`
 
@@ -230,7 +230,8 @@ constraints:
 There is no body. A [term](#terms) of this file may add to the name. This
 file reads the name as it reads a given variable: a quantity over the frame, of
 degree one. A `where` does not read it, because a mask is built before any
-variable exists. A name declared under both `expressions:` and
+variable exists. A predicate another file defines is read as a
+[given mask](#given-masks) instead. A name declared under both `expressions:` and
 `given: expressions:` is refused. The typeset legend lists a given expression
 under _Given_.
 
@@ -334,6 +335,47 @@ like any other.
   fragment '#2' adds 't' to 'injection', and 't' reads 'injection' back through 'x' of '#1', so the sum would define itself. A term may not read what reads its sum: write 't' from something else, or define 'x' without 'injection'.
   ```
 
+### `given: masks`
+
+A given mask is a [mask](named.md#masks) this file reads and another file
+defines.
+
+```yaml
+dimensions:
+  period: { dtype: int, ordered: true }
+  generator: { dtype: str }
+given:
+  variables:
+    p: { dims: [period, generator] }
+  masks:
+    stands:
+      dims: [period, generator]
+      description: the generator stands in this period
+parameters:
+  ramp: { dims: [generator] }
+constraints:
+  ramp_up:
+    dims: [period, generator]
+    where: stands AND shift(stands, along=period, offset=1)
+    expression: p - shift(p, along=period, offset=1) <= ramp
+```
+
+| Field         |                                                        |                |
+| ------------- | ------------------------------------------------------ | -------------- |
+| `dims`        | required. The dimensions the definer's predicate reads |                |
+| `description` | free text                                              | default `null` |
+
+There is no predicate. A `where` reads the name as data over the frame, true
+or false at each coordinate. A `where` may read a given mask where it may not
+read a given expression, since a mask reads nothing a solve decides. In
+arithmetic the name is refused, as a mask is. The typeset legend lists a given
+mask under _Given_.
+
+[`merge`](../../howto/compose.md#a-library-of-components) folds a given mask
+into the mask another fragment defines. The `dims` name the dimensions the
+definer's predicate reads, no more and no fewer. A reading that names a
+different set is refused, with both frames.
+
 ## `constraints`
 
 One block is one rule. The name of the block is the name of the constraint.
diff --git a/docs/reference/language/expressions.md b/docs/reference/language/expressions.md
index 29f9ecb7..cdbcfb3c 100644
--- a/docs/reference/language/expressions.md
+++ b/docs/reference/language/expressions.md
@@ -73,7 +73,7 @@ a square.
 ## Name resolution
 
 One flat namespace covers dimensions, relations, parameters, variables, named
-expressions, macros and the built-in operators. A collision is a load error that
+expressions, masks, macros and the built-in operators. A collision is a load error that
 names both declarations, and nothing shadows anything.
 
 Position decides which kinds of name are legal:
@@ -83,7 +83,7 @@ Position decides which kinds of name are legal:
 | expression (`p * cost`)                | a variable, or a parameter whose values are numbers ([dtype](declarations.md#parameters))                                |
 | dimension argument (`over=`, `along=`) | a dimension, or a list of them for `over=`. Beside `by=`, a name in `over=` is a column of the relation where it has one |
 | column argument (`by=`, `within=`)     | columns of one relation, written `relation[column]` or `relation[column, …]`                                             |
-| `where` string                         | a parameter, variable, dimension or relation ([where strings](#where-strings))                                           |
+| `where` string                         | a parameter, variable, dimension, relation or mask ([where strings](#where-strings))                                     |
 | `bounds.lower` / `bounds.upper`        | a parameter name, or a number                                                                                            |
 | the `edge` key of `shift`              | `'wrap'` in quotes, or a bare number                                                                                     |
 | `dual` argument (`dual(c)`)            | a constraint. It resolves against the constraints alone ([named expressions](named.md#reading-a-constraints-dual))       |
@@ -149,6 +149,7 @@ QUOTED     ::= "'" chars "'" | '"' chars '"'
 | `name` (bare)                             | variable                   | The variable exists at this coordinate                                                                                                                                                                 |
 | `name` (bare)                             | relation                   | A row exists, read at the relation's key. A relation may be [partial](relations.md#the-data-contract), and this selects the labels that do map                                                         |
 | `name` (bare)                             | dimension                  | A load error. It would be true everywhere                                                                                                                                                              |
+| `name` (bare)                             | mask                       | The mask's predicate ([masks](named.md#masks)). A given mask is true or false at each coordinate, as a `bool` parameter is                                                                             |
 | `name OP value`                           | parameter                  | Element-wise, and a null compares false                                                                                                                                                                |
 | `name OP value`                           | dimension                  | A filter on the frame's own coordinate column                                                                                                                                                          |
 | `name OP value`, `name[col] OP value`     | relation                   | A filter on a value column, read at the relation's key. Name the column where the key determines several. A comparison reads one column                                                                |
diff --git a/docs/reference/language/file.md b/docs/reference/language/file.md
index d635d178..56b28ae5 100644
--- a/docs/reference/language/file.md
+++ b/docs/reference/language/file.md
@@ -5,8 +5,8 @@ SPDX-License-Identifier: CC-BY-4.0
 
 # File shape
 
-A spec file is a YAML mapping with **twelve declaration keys**, plus
-`version` and `description`. Any subset of the twelve is accepted.
+A spec file is a YAML mapping with **thirteen declaration keys**, plus
+`version` and `description`. Any subset of the thirteen is accepted.
 
 | Key           |                                                                                                   |
 | ------------- | ------------------------------------------------------------------------------------------------- |
@@ -18,6 +18,7 @@ A spec file is a YAML mapping with **twelve declaration keys**, plus
 | `constraints` | the rules those decisions obey                                                                    |
 | `objective`   | what is minimised or maximised                                                                    |
 | `expressions` | named quantities, reusable in the math and readable after a solve ([named expressions](named.md)) |
+| `masks`       | named `where` predicates, read by name wherever a `where` string is ([masks](named.md#masks))     |
 | `macros`      | templates that take arguments ([macros](named.md#macros))                                         |
 | `piecewise`   | piecewise-linear curves ([piecewise](piecewise.md))                                               |
 | `sos`         | special-ordered sets ([sos](piecewise.md#sos))                                                    |
diff --git a/docs/reference/language/index.md b/docs/reference/language/index.md
index 59384fc7..c9c24bad 100644
--- a/docs/reference/language/index.md
+++ b/docs/reference/language/index.md
@@ -46,7 +46,7 @@ names the fix.
 
 | #   | Rule                                                                                                                                                                  |                                                                 |
 | --- | --------------------------------------------------------------------------------------------------------------------------------------------------------------------- | --------------------------------------------------------------- |
-| 1   | A file has twelve declaration keys, plus `version` and `description`. An unknown key is refused, with the nearest valid key named.                                    | [File shape](file.md)                                           |
+| 1   | A file has thirteen declaration keys, plus `version` and `description`. An unknown key is refused, with the nearest valid key named.                                  | [File shape](file.md)                                           |
 | 2   | Everything that can be checked without data is checked when the file loads.                                                                                           | [Errors](errors.md)                                             |
 | 3   | Every name is declared once. A parameter and a dimension both called `snapshot` is refused.                                                                           | [Names](expressions.md#name-resolution)                         |
 | 4   | Where a name may stand depends on what it is. A dimension follows `over=` or `along=`, and is never multiplied.                                                       | [Names](expressions.md#name-resolution)                         |
diff --git a/docs/reference/language/named.md b/docs/reference/language/named.md
index 30bbc682..76ebc2ca 100644
--- a/docs/reference/language/named.md
+++ b/docs/reference/language/named.md
@@ -3,11 +3,12 @@ SPDX-FileCopyrightText: mathspec contributors
 SPDX-License-Identifier: CC-BY-4.0
 -->
 
-# Named expressions and macros
+# Named expressions, masks and macros
 
 An `expressions:` entry names a quantity once, for the math to read or for a
-solve to report. A `macros:` entry is a template with arguments, substituted
-before anything reads it.
+solve to report. A `masks:` entry names a `where` predicate once, for every
+`where:` that reads it. A `macros:` entry is a template with arguments,
+substituted before anything reads it.
 
 ## `expressions`
 
@@ -186,6 +187,84 @@ duals are opposite.
 
 A row that `c`'s `where:` deletes has no dual.
 
+## `masks`
+
+A mask names a [`where` predicate](expressions.md#where-strings) once. A
+`where:`, a `when:` or a `holds:` then reads it by name:
+
+```yaml
+dimensions:
+  period: { dtype: int, ordered: true }
+  generator: { dtype: str }
+parameters:
+  build_year: { dims: [generator] }
+  lifetime: { dims: [generator] }
+  period_year: { dims: [period] }
+  p_nom: { dims: [generator] }
+masks:
+  stands:
+    where: build_year <= period_year AND period_year < build_year + lifetime
+    description: the generator stands in this period
+variables:
+  p:
+    dims: [period, generator]
+    where: stands
+    bounds: { lower: 0, upper: p_nom }
+constraints:
+  ramp_up:
+    dims: [period, generator]
+    where: stands AND shift(stands, along=period, offset=1)
+    expression: p - shift(p, along=period, offset=1) <= 0.5 * p_nom
+```
+
+The typeset document prints the mask's symbol where it is read. The symbol is
+upright, as data is. The predicate prints once, under _Masks_, with ⟺ where an
+expression prints =:
+
+```math
+\mathrm{stands}_{e,g} \iff \mathrm{build\_year}_{g} \le \mathrm{period\_year}_{e} \wedge \mathrm{period\_year}_{e} < \mathrm{build\_year}_{g} + \mathrm{lifetime}_{g} \qquad \forall\, e \in \mathcal{E},\ g \in \mathcal{G}
+```
+
+```math
+p_{e,g} - p_{e - 1,g} \le 0.5 \cdot \mathrm{p}^{\mathrm{nom}}_{g} \qquad \forall\, e \in \mathcal{E},\ g \in \mathcal{G} \,:\, \mathrm{stands}_{e,g} \wedge \mathrm{stands}_{e - 1,g}
+```
+
+| Field         |                                                 |                |
+| ------------- | ----------------------------------------------- | -------------- |
+| `where`       | required. The predicate, in the `where` grammar |                |
+| `description` | free text                                       | default `null` |
+
+An entry with no `description:` may be the bare `where` string.
+
+- **A bare mask name stands for its predicate.** It does so in a `where:`, a
+  `when:` and a `holds:`, under `NOT`, and inside `count`, `shift` and `at`.
+  The rows are the rows the predicate written out gives.
+- **The predicate gives the frame.** A mask runs over the dimensions its
+  predicate reads, in the order `dimensions:` declares them, and the symbol
+  prints with those indices. A mask declares no `dims:`. A use over more
+  dimensions reads the mask as the same along the rest, and `shift` reads it
+  back along a dimension of its frame only.
+- **A mask may read another mask**, and a named expression that reads data
+  only. A cycle is refused with its chain:
+
+  ```text
+  Mask 'again': circular mask reference: again -> again
+  ```
+
+- **A mask is never a number.** In arithmetic or in a comparison it is
+  refused:
+
+  ```text
+  Named expression 'e': 'stands' is a mask, which is true or false where it is read, and not a number. Write it bare in the where — stands, or NOT stands — rather than comparing it or computing with it.
+  ```
+
+- **A predicate that folds to `True` or `False` is refused**, since it names
+  every row or none.
+- **A variable's own `where:` may not ask, through a mask, whether the
+  variable exists.** The loader refuses this as it refuses the bare name.
+
+Another file reads a mask under [`given: masks`](declarations.md#given-masks).
+
 ## `macros`
 
 A macro is a template that takes arguments and is substituted into an expression
diff --git a/docs/reference/notation.md b/docs/reference/notation.md
index 0938e0d3..cb315bae 100644
--- a/docs/reference/notation.md
+++ b/docs/reference/notation.md
@@ -129,6 +129,13 @@ parameters:
 | $`\mathit{marginal\_price}`$ | `marginal_price` over $`\mathcal{T} \times \mathcal{B}`$ |
 | $`\mathrm{startup\_cost}`$ | `startup_cost` over $`\mathcal{T} \times \mathcal{G}`$ — what starting a unit in this snapshot costs, which the horizon's edge changes |
 
+#### Masks
+
+| Symbol | Meaning |
+|---|---|
+| $`\mathrm{dispatchable}`$ | `dispatchable` over $`\mathcal{G}`$ — a unit that dispatches and cannot be turned down |
+| $`\mathrm{priced\_dispatch}`$ | `priced_dispatch` over $`\mathcal{G}`$ |
+
 Upright is what the data supplies — a parameter such as $`\mathrm{p}^{\mathrm{max}}`$, a coordinate map, a label — and italic is what the solver chooses, such as $`p`$. An index is italic too, being what a quantifier chooses, and a set is script.
 
 $`t \ominus k`$ denotes cyclic translation: index $`t-k`$ taken modulo the size of the dimension (`roll`). Plain $`t-k`$ (`shift`) has no wraparound — terms translated past the edge are simply absent.
@@ -793,6 +800,51 @@ expressions:
 \mathit{marginal\_price}_{t,b} = \lambda_{\mathrm{balance},t,b} \qquad \forall\, t \in \mathcal{T},\ b \in \mathcal{B}
 ```
 
+### Named masks
+
+#### Named mask
+
+a named predicate with its words: a use prints the symbol over the dims its predicate reads, the predicate prints once
+
+```yaml
+masks:
+  dispatchable:
+    where: "p_max > 0 AND NOT is_flexible"
+```
+
+```math
+\mathrm{dispatchable}_{g} \iff \mathrm{p}^{\mathrm{max}}_{g} > 0 \wedge \neg \mathrm{is\_flexible}_{g} \qquad \forall\, g \in \mathcal{G}
+```
+
+#### Mask that reads a mask
+
+the one-line form, reading another mask and a data-only entry
+
+```yaml
+masks:
+  priced_dispatch: "dispatchable AND spend_cap > 0"
+```
+
+```math
+\mathrm{priced\_dispatch}_{g} \iff \mathrm{dispatchable}_{g} \wedge \mathrm{spend}^{\mathrm{cap}}_{g} > 0 \qquad \forall\, g \in \mathcal{G}
+```
+
+#### Mask in a condition
+
+a mask as the where, beside a condition of the constraint's own
+
+```yaml
+constraints:
+  masked:
+    dims: [snapshot, generator]
+    where: "priced_dispatch AND position(snapshot) > 0"
+    expression: p <= p_max
+```
+
+```math
+p_{t,g} \le \mathrm{p}^{\mathrm{max}}_{g} \qquad \forall\, t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{priced\_dispatch}_{g} \wedge \mathrm{pos}(t) > 0
+```
+
 ### Shifts
 
 #### Cyclic and acyclic shift
diff --git a/docs/reference/reading.md b/docs/reference/reading.md
index 9677b2a9..fc6b5036 100644
--- a/docs/reference/reading.md
+++ b/docs/reference/reading.md
@@ -132,6 +132,12 @@ entry's expression, the same object that `program.expressions[name].expression`
 holds, and its value is the body's value. `children()` steps into the body, so
 a walk reads through it.
 
+A `NamedMask` stands where a `masks:` entry is read. Its `body` is the entry's
+predicate, the root of `program.masks[name].where`, and it is true where the
+body is true. `where_children()` steps into the body, so `.atoms`,
+`.names_read` and `.dims` read through it, and a consumer that builds rows
+needs nothing from `program.masks`.
+
 Every `where` arrives as a `Mask`. Its `.root` is the resolved predicate. The
 mask also answers four questions:
 
@@ -166,11 +172,14 @@ stands at a mask's root or nowhere. A `Region`'s `when` is a `Mask` too.
 ## What a program does not build
 
 `program.given.parameters`, `program.given.variables`,
-`program.given.expressions` and `program.given.constraints` name what the spec
-reads and does not build ([given](language/declarations.md#given)). Every
-other group is a build instruction. These four are names to look up in the
-model this one is layered onto. An expression reads a given expression as a
-`Variable` of that name, over the frame under `program.given.expressions`.
+`program.given.expressions`, `program.given.masks` and
+`program.given.constraints` name what the spec reads and does not build
+([given](language/declarations.md#given)). Every other group is a build
+instruction. These five are names to look up in the model this one is layered
+onto. An expression reads a given expression as a `Variable` of that name,
+over the frame under `program.given.expressions`. A `where` reads a given mask
+as a `ParameterDefined` of that name: boolean data over the frame under
+`program.given.masks`.
 An entry of `program.expressions` whose `adds_to` names a given expression is
 a term this file adds to it. The name is still one the program reads and does
 not build.
@@ -197,7 +206,7 @@ layer.given.constraints['balance'].dims  # ('snapshot', 'bus')
 The host model provides each name: it holds a column or a row family of that
 name. A consumer that builds the program checks that the host provides each
 name on the same frame, and refuses the program where it does not. A consumer
-with no host refuses a program whose four groups are not all empty. `advice`
+with no host refuses a program whose five groups are not all empty. `advice`
 returns one note of kind `given` per name
 ([what `advice` warns about](language/errors.md#what-advice-warns-about)).
 
diff --git a/docs/reference/typeset.md b/docs/reference/typeset.md
index 90b85ece..8db03f81 100644
--- a/docs/reference/typeset.md
+++ b/docs/reference/typeset.md
@@ -57,6 +57,9 @@ a flag. The [Python API](api.md#typesetting) gives each signature.
   `cases:` block, a [reported entry](language/named.md#reported-expressions)
   and a [term](language/declarations.md#terms) keep their definition line
   under either `inline_expressions` setting.
+- A [mask](language/named.md#masks) prints its upright symbol where it is
+  read and its predicate once, under a **Masks** heading, with ⟺. It prints
+  by symbol under either `inline_expressions` setting.
 - Wherever the math moves an index, which every `shift` does, the document
   prints a line saying what that notation means.
 - A file that does not load does not print.
@@ -80,8 +83,8 @@ dimension, parameter and variable.
 ## Printing one declaration on its own
 
 `typeset_declaration` returns the line the document prints for one named
-expression, constraint, assumption or variable, with its quantifier and without
-a document, a label, a number or math delimiters:
+expression, mask, constraint, assumption, curve or variable, with its
+quantifier and without a document, a label, a number or math delimiters:
 
 ```python
 ms.typeset_declaration('spec.yaml', 'spend', 'latex')
@@ -103,7 +106,7 @@ A line on its own has no _Definitions_ section beside it, so the plain named
 expressions it uses are substituted. A cased expression prints by symbol, and a
 second call with its name prints its block.
 
-A name that is none of the four kinds is refused with the near miss. A name
+A name that is none of the six kinds is refused with the near miss. A name
 declared as two of them, such as a constraint and a variable, is refused too.
 
 ## Symbol tables
diff --git a/examples/pypsa.yaml b/examples/pypsa.yaml
index c51b7a09..cb533170 100644
--- a/examples/pypsa.yaml
+++ b/examples/pypsa.yaml
@@ -1453,21 +1453,21 @@ variables:
       the rows below cap at one, or at the module count where the build is
       modular
     dims: [scenario, snapshot, generator]
-    where: Generator_committable AND Generator_active
+    where: Generator_committed
     domain: integer
     bounds:
       lower: 0
   Generator_start_up:
     description: "`Generator-start_up` — how much of a committable unit turns on this snapshot, capped as the status is"
     dims: [scenario, snapshot, generator]
-    where: Generator_committable AND Generator_active
+    where: Generator_committed
     domain: integer
     bounds:
       lower: 0
   Generator_shut_down:
     description: "`Generator-shut_down` — how much of a committable unit turns off this snapshot, capped as the status is"
     dims: [scenario, snapshot, generator]
-    where: Generator_committable AND Generator_active
+    where: Generator_committed
     domain: integer
     bounds:
       lower: 0
@@ -1492,9 +1492,7 @@ variables:
       `Generator-maintenance_capacity` — the chosen build while in maintenance, zero
       otherwise: the product the `maintcap` rows linearize
     dims: [scenario, snapshot, generator]
-    where: >-
-      Generator_maintainable AND Generator_p_nom_extendable
-      AND NOT (Generator_committable AND Generator_p_nom_mod > 0) AND Generator_active
+    where: Generator_maint_ext
     absence: zero
     bounds:
       lower: 0
@@ -1505,8 +1503,9 @@ variables:
       maintenance may also be off
     dims: [scenario, snapshot, generator]
     where: >-
-      Generator_maintainable AND Generator_committable
-      AND NOT (Generator_p_nom_extendable AND NOT (Generator_p_nom_mod > 0)) AND Generator_active
+      Generator_maintainable
+      AND Generator_committed
+      AND NOT (Generator_p_nom_extendable AND NOT (Generator_p_nom_mod > 0))
     absence: zero
     bounds:
       lower: 0
@@ -1523,21 +1522,21 @@ variables:
       the rows below cap at one, or at the module count where the build is
       modular
     dims: [scenario, snapshot, link]
-    where: Link_committable AND Link_active
+    where: Link_committed
     domain: integer
     bounds:
       lower: 0
   Link_start_up:
     description: "`Link-start_up` — how much of a committable link turns on this snapshot, capped as the status is"
     dims: [scenario, snapshot, link]
-    where: Link_committable AND Link_active
+    where: Link_committed
     domain: integer
     bounds:
       lower: 0
   Link_shut_down:
     description: "`Link-shut_down` — how much of a committable link turns off this snapshot, capped as the status is"
     dims: [scenario, snapshot, link]
-    where: Link_committable AND Link_active
+    where: Link_committed
     domain: integer
     bounds:
       lower: 0
@@ -1562,9 +1561,7 @@ variables:
       `Link-maintenance_capacity` — the chosen build while in maintenance, zero
       otherwise: the product the `maintcap` rows linearize
     dims: [scenario, snapshot, link]
-    where: >-
-      Link_maintainable AND Link_p_nom_extendable
-      AND NOT (Link_committable AND Link_p_nom_mod > 0) AND Link_active
+    where: Link_maint_ext
     absence: zero
     bounds:
       lower: 0
@@ -1574,9 +1571,7 @@ variables:
       otherwise: the product the `maint-status` rows linearize, so a unit in
       maintenance may also be off
     dims: [scenario, snapshot, link]
-    where: >-
-      Link_maintainable AND Link_committable
-      AND NOT (Link_p_nom_extendable AND NOT (Link_p_nom_mod > 0)) AND Link_active
+    where: Link_maintainable AND Link_committed AND NOT (Link_p_nom_extendable AND NOT (Link_p_nom_mod > 0))
     absence: zero
     bounds:
       lower: 0
@@ -1593,21 +1588,21 @@ variables:
       the rows below cap at one, or at the module count where the build is
       modular
     dims: [scenario, snapshot, process]
-    where: Process_committable AND Process_active
+    where: Process_committed
     domain: integer
     bounds:
       lower: 0
   Process_start_up:
     description: "`Process-start_up` — how much of a committable process turns on this snapshot, capped as the status is"
     dims: [scenario, snapshot, process]
-    where: Process_committable AND Process_active
+    where: Process_committed
     domain: integer
     bounds:
       lower: 0
   Process_shut_down:
     description: "`Process-shut_down` — how much of a committable process turns off this snapshot, capped as the status is"
     dims: [scenario, snapshot, process]
-    where: Process_committable AND Process_active
+    where: Process_committed
     domain: integer
     bounds:
       lower: 0
@@ -1632,9 +1627,7 @@ variables:
       `Process-maintenance_capacity` — the chosen build while in maintenance, zero
       otherwise: the product the `maintcap` rows linearize
     dims: [scenario, snapshot, process]
-    where: >-
-      Process_maintainable AND Process_p_nom_extendable
-      AND NOT (Process_committable AND Process_p_nom_mod > 0) AND Process_active
+    where: Process_maint_ext
     absence: zero
     bounds:
       lower: 0
@@ -1645,8 +1638,9 @@ variables:
       maintenance may also be off
     dims: [scenario, snapshot, process]
     where: >-
-      Process_maintainable AND Process_committable
-      AND NOT (Process_p_nom_extendable AND NOT (Process_p_nom_mod > 0)) AND Process_active
+      Process_maintainable
+      AND Process_committed
+      AND NOT (Process_p_nom_extendable AND NOT (Process_p_nom_mod > 0))
     absence: zero
     bounds:
       lower: 0
@@ -1662,7 +1656,7 @@ variables:
       cost and held up by the cuts; absent, and zero in the balance, where
       the network is lossless
     dims: [scenario, snapshot, line]
-    where: transmission_losses AND Line_active
+    where: Line_lossy
     absence: zero
     bounds:
       lower: 0
@@ -1679,7 +1673,7 @@ variables:
       a line does; absent, and zero in the balance, where the network is
       lossless
     dims: [scenario, snapshot, transformer]
-    where: transmission_losses AND Transformer_active
+    where: Transformer_lossy
     absence: zero
     bounds:
       lower: 0
@@ -2520,6 +2514,127 @@ expressions:
       the voltage angle differences around a cycle: every branch flow times
       its cycle weight, and every transformer phase shift
 
+masks:
+  Generator_com_ext:
+    description: >-
+      a committable generator with an extendable, non-modular build that
+      stands in the snapshot's period — PyPSA's `com-ext` rows, whose status
+      is relaxed against the chosen build
+    where: >-
+      Generator_committable
+      AND Generator_p_nom_extendable
+      AND NOT (Generator_p_nom_mod > 0)
+      AND Generator_active
+  Generator_maint_ext:
+    description: >-
+      a maintainable generator with an extendable build, unless it is
+      committable and modular, that stands in the snapshot's period — the
+      maintenance rows against the chosen build
+    where: >-
+      Generator_maintainable
+      AND Generator_p_nom_extendable
+      AND NOT (Generator_committable AND Generator_p_nom_mod > 0)
+      AND Generator_active
+  Generator_committed:
+    description: >-
+      a committable generator that stands in the snapshot's period — every
+      unit-commitment row's set
+    where: Generator_committable AND Generator_active
+  Generator_ramps_from_previous:
+    description: >-
+      a snapshot whose ramp reads a previous output — any snapshot but its
+      period's first, and the horizon's first where the generator comes in off
+      or carries an initial output
+    where: >-
+      position(snapshot, within=snapshot_period[period]) > 0 OR (position(snapshot) == 0 AND
+      (Generator_status_initial == 0 OR Generator_p_init))
+  Link_com_ext:
+    description: >-
+      a committable link with an extendable, non-modular build that stands in
+      the snapshot's period — PyPSA's `com-ext` rows, whose status is relaxed
+      against the chosen build
+    where: >-
+      Link_committable
+      AND Link_p_nom_extendable
+      AND NOT (Link_p_nom_mod > 0)
+      AND Link_active
+  Link_maint_ext:
+    description: >-
+      a maintainable link with an extendable build, unless it is committable
+      and modular, that stands in the snapshot's period — the maintenance rows
+      against the chosen build
+    where: >-
+      Link_maintainable
+      AND Link_p_nom_extendable
+      AND NOT (Link_committable AND Link_p_nom_mod > 0)
+      AND Link_active
+  Link_committed:
+    description: >-
+      a committable link that stands in the snapshot's period — every
+      unit-commitment row's set
+    where: Link_committable AND Link_active
+  Link_ramps_from_previous:
+    description: >-
+      a snapshot whose ramp reads a previous output — any snapshot but its
+      period's first, and the horizon's first where the link comes in off or
+      carries an initial output
+    where: >-
+      position(snapshot, within=snapshot_period[period]) > 0 OR (position(snapshot) == 0 AND
+      (Link_status_initial == 0 OR Link_p_init))
+  Process_com_ext:
+    description: >-
+      a committable process with an extendable, non-modular build that stands
+      in the snapshot's period — PyPSA's `com-ext` rows, whose status is
+      relaxed against the chosen build
+    where: >-
+      Process_committable
+      AND Process_p_nom_extendable
+      AND NOT (Process_p_nom_mod > 0)
+      AND Process_active
+  Process_maint_ext:
+    description: >-
+      a maintainable process with an extendable build, unless it is
+      committable and modular, that stands in the snapshot's period — the
+      maintenance rows against the chosen build
+    where: >-
+      Process_maintainable
+      AND Process_p_nom_extendable
+      AND NOT (Process_committable AND Process_p_nom_mod > 0)
+      AND Process_active
+  Process_committed:
+    description: >-
+      a committable process that stands in the snapshot's period — every
+      unit-commitment row's set
+    where: Process_committable AND Process_active
+  Process_ramps_from_previous:
+    description: >-
+      a snapshot whose ramp reads a previous output — any snapshot but its
+      period's first, and the horizon's first where the process comes in off
+      or carries an initial output
+    where: >-
+      position(snapshot, within=snapshot_period[period]) > 0 OR (position(snapshot) == 0 AND
+      (Process_status_initial == 0 OR Process_p_init))
+  StorageUnit_fix:
+    description: >-
+      a storage unit with a fixed build that stands in the snapshot's period —
+      PyPSA's `fix` rows
+    where: NOT StorageUnit_p_nom_extendable AND StorageUnit_active
+  StorageUnit_ext:
+    description: >-
+      a storage unit with an extendable build that stands in the snapshot's
+      period — PyPSA's `ext` rows
+    where: StorageUnit_p_nom_extendable AND StorageUnit_active
+  Line_lossy:
+    description: >-
+      a line that stands in the snapshot's period, where the run models
+      transmission losses
+    where: transmission_losses AND Line_active
+  Transformer_lossy:
+    description: >-
+      a transformer that stands in the snapshot's period, where the run models
+      transmission losses
+    where: transmission_losses AND Transformer_active
+
 constraints:
   Generator_fix_p_lower:
     description: "`Generator-fix-p-lower` — a fixed generator outputs at least its minimum"
@@ -2639,54 +2754,54 @@ constraints:
   StorageUnit_fix_p_dispatch_lower:
     description: "`StorageUnit-fix-p_dispatch-lower` — dispatch is non-negative"
     dims: [scenario, snapshot, storage_unit]
-    where: not StorageUnit_p_nom_extendable AND StorageUnit_active
+    where: StorageUnit_fix
     expression: StorageUnit_p_dispatch >= 0
   StorageUnit_fix_p_dispatch_upper:
     description: "`StorageUnit-fix-p_dispatch-upper` — a fixed unit dispatches at most its nominal power"
     dims: [scenario, snapshot, storage_unit]
-    where: not StorageUnit_p_nom_extendable AND StorageUnit_active
+    where: StorageUnit_fix
     expression: StorageUnit_p_dispatch <= StorageUnit_p_max_pu * StorageUnit_p_nom
   StorageUnit_fix_p_store_lower:
     description: "`StorageUnit-fix-p_store-lower` — storing is non-negative"
     dims: [scenario, snapshot, storage_unit]
-    where: not StorageUnit_p_nom_extendable AND StorageUnit_active
+    where: StorageUnit_fix
     expression: StorageUnit_p_store >= 0
   StorageUnit_fix_p_store_upper:
     description: >-
       `StorageUnit-fix-p_store-upper` — a fixed unit stores at most its
       nominal power, the minimum-per-unit column carrying that cap negated
     dims: [scenario, snapshot, storage_unit]
-    where: not StorageUnit_p_nom_extendable AND StorageUnit_active
+    where: StorageUnit_fix
     expression: StorageUnit_p_store <= -StorageUnit_p_min_pu * StorageUnit_p_nom
   StorageUnit_fix_state_of_charge_lower:
     description: "`StorageUnit-fix-state_of_charge-lower` — charge is non-negative"
     dims: [scenario, snapshot, storage_unit]
-    where: not StorageUnit_p_nom_extendable AND StorageUnit_active
+    where: StorageUnit_fix
     expression: StorageUnit_state_of_charge >= 0
   StorageUnit_fix_state_of_charge_upper:
     description: "`StorageUnit-fix-state_of_charge-upper` — a fixed unit holds at most its hours at nominal power"
     dims: [scenario, snapshot, storage_unit]
-    where: not StorageUnit_p_nom_extendable AND StorageUnit_active
+    where: StorageUnit_fix
     expression: StorageUnit_state_of_charge <= StorageUnit_max_hours * StorageUnit_p_nom
   Generator_com_p_lower:
     description: "`Generator-com-p-lower` — a committed unit outputs at least its minimum; off, at least nothing"
     dims: [scenario, snapshot, generator]
-    where: Generator_committable AND not Generator_p_nom_extendable AND NOT (Generator_p_nom_mod > 0) AND Generator_active
+    where: Generator_committed AND NOT Generator_p_nom_extendable AND NOT (Generator_p_nom_mod > 0)
     expression: Generator_p >= Generator_p_min_pu * Generator_p_nom * (Generator_status - Generator_maintenance_pu * Generator_maintenance_status)
   Generator_com_p_upper:
     description: "`Generator-com-p-upper` — a committed unit outputs at most what is available; off, at most nothing"
     dims: [scenario, snapshot, generator]
-    where: Generator_committable AND not Generator_p_nom_extendable AND NOT (Generator_p_nom_mod > 0) AND Generator_active
+    where: Generator_committed AND NOT Generator_p_nom_extendable AND NOT (Generator_p_nom_mod > 0)
     expression: Generator_p <= Generator_p_max_pu * Generator_p_nom * (Generator_status - Generator_maintenance_pu * Generator_maintenance_status)
   Generator_com_transition_start_up:
     description: "`Generator-com-transition-start-up` — turning on is a start, counted against the state the unit carried into the snapshot"
     dims: [scenario, snapshot, generator]
-    where: Generator_committable AND Generator_active
+    where: Generator_committed
     expression: Generator_start_up >= Generator_status - Generator_previous_status
   Generator_com_transition_shut_down:
     description: "`Generator-com-transition-shut-down` — turning off is a stop, counted against the state the unit carried into the snapshot"
     dims: [scenario, snapshot, generator]
-    where: Generator_committable AND Generator_active
+    where: Generator_committed
     expression: Generator_shut_down >= Generator_previous_status - Generator_status
   Generator_com_up_time:
     description: >-
@@ -2694,7 +2809,7 @@ constraints:
       is still on. The first snapshot's share of the window is the brought-in
       up time's, which the must-stay-up mask carries
     dims: [scenario, snapshot, generator]
-    where: Generator_committable AND Generator_min_up_time > 0 AND position(snapshot) > 0 AND Generator_active
+    where: Generator_committed AND Generator_min_up_time > 0 AND position(snapshot) > 0
     expression: sum_back(Generator_start_up, along=snapshot, window=Generator_min_up_time) <= Generator_status
   Generator_com_down_time:
     description: >-
@@ -2702,19 +2817,19 @@ constraints:
       time is still off. The first snapshot's share of the window is the
       brought-in down time's, which the must-stay-down mask carries
     dims: [scenario, snapshot, generator]
-    where: Generator_committable AND Generator_min_down_time > 0 AND position(snapshot) > 0 AND Generator_active
+    where: Generator_committed AND Generator_min_down_time > 0 AND position(snapshot) > 0
     expression: sum_back(Generator_shut_down, along=snapshot, window=Generator_min_down_time) <= 1 - Generator_status
   Generator_com_status_must_stay_up:
     description: "`Generator-com-status-min_up_time_must_stay_up` — a unit still serving the up time it brought in stays on"
     dims: [scenario, snapshot, generator]
-    where: Generator_committable AND Generator_must_stay_up AND Generator_active
+    where: Generator_committed AND Generator_must_stay_up
     expression: Generator_status == 1
   Generator_com_status_must_stay_down:
     description: >-
       `Generator-com-status-min_down_time_must_stay_up` — a unit still serving
       the down time it brought in stays off; PyPSA names the row `_must_stay_up`
     dims: [scenario, snapshot, generator]
-    where: Generator_committable AND Generator_must_stay_down AND Generator_active
+    where: Generator_committed AND Generator_must_stay_down
     expression: Generator_status == 0
   Generator_p_ramp_limit_up_run_big_m:
     description: >-
@@ -2723,10 +2838,9 @@ constraints:
       releases the row in the snapshot it turns on
     dims: [scenario, snapshot, generator]
     where: >-
-      Generator_committable AND Generator_p_nom_extendable AND NOT (Generator_p_nom_mod > 0)
+      Generator_com_ext
       AND (Generator_ramp_limit_up OR Generator_ramp_limit_start_up)
-      AND (position(snapshot, within=snapshot_period[period]) > 0 OR (position(snapshot) == 0 AND (Generator_status_initial == 0 OR Generator_p_init)))
-      AND Generator_active
+      AND Generator_ramps_from_previous
     expression: >-
       Generator_p - Generator_previous_p <=
       Generator_ramp_up_rate * Generator_p_nom_ext
@@ -2738,10 +2852,9 @@ constraints:
       the chosen build; the big M releases the row everywhere else
     dims: [scenario, snapshot, generator]
     where: >-
-      Generator_committable AND Generator_p_nom_extendable AND NOT (Generator_p_nom_mod > 0)
+      Generator_com_ext
       AND (Generator_ramp_limit_up OR Generator_ramp_limit_start_up)
-      AND (position(snapshot, within=snapshot_period[period]) > 0 OR (position(snapshot) == 0 AND (Generator_status_initial == 0 OR Generator_p_init)))
-      AND Generator_active
+      AND Generator_ramps_from_previous
     expression: >-
       Generator_p - Generator_previous_p <=
       Generator_start_up_rate * Generator_p_nom_ext
@@ -2753,10 +2866,9 @@ constraints:
       releases the row in the snapshot it turns off
     dims: [scenario, snapshot, generator]
     where: >-
-      Generator_committable AND Generator_p_nom_extendable AND NOT (Generator_p_nom_mod > 0)
+      Generator_com_ext
       AND (Generator_ramp_limit_down OR Generator_ramp_limit_shut_down)
-      AND (position(snapshot, within=snapshot_period[period]) > 0 OR (position(snapshot) == 0 AND (Generator_status_initial == 0 OR Generator_p_init)))
-      AND Generator_active
+      AND Generator_ramps_from_previous
     expression: >-
       Generator_previous_p - Generator_p <=
       Generator_ramp_down_rate * Generator_p_nom_ext
@@ -2768,10 +2880,9 @@ constraints:
       the chosen build; the big M releases the row everywhere else
     dims: [scenario, snapshot, generator]
     where: >-
-      Generator_committable AND Generator_p_nom_extendable AND NOT (Generator_p_nom_mod > 0)
+      Generator_com_ext
       AND (Generator_ramp_limit_down OR Generator_ramp_limit_shut_down)
-      AND (position(snapshot, within=snapshot_period[period]) > 0 OR (position(snapshot) == 0 AND (Generator_status_initial == 0 OR Generator_p_init)))
-      AND Generator_active
+      AND Generator_ramps_from_previous
     expression: >-
       Generator_previous_p - Generator_p <=
       Generator_shut_down_rate * Generator_p_nom_ext
@@ -2786,19 +2897,19 @@ constraints:
       `Generator-com-ext-p-upper-cap` — a committed extendable unit outputs
       at most what is available of the chosen build, whatever its status
     dims: [scenario, snapshot, generator]
-    where: Generator_committable AND Generator_p_nom_extendable AND NOT (Generator_p_nom_mod > 0) AND Generator_active
+    where: Generator_com_ext
     expression: Generator_p <= Generator_p_max_pu * (Generator_p_nom_ext - Generator_maintenance_pu * Generator_maintenance_capacity)
   Generator_com_ext_p_upper_big_m:
     description: "`Generator-com-ext-p-upper-bigM` — off, a unit outputs nothing; on, the big M is no bound"
     dims: [scenario, snapshot, generator]
-    where: Generator_committable AND Generator_p_nom_extendable AND NOT (Generator_p_nom_mod > 0) AND Generator_active
+    where: Generator_com_ext
     expression: Generator_p <= Generator_big_m * Generator_status
   Generator_com_ext_p_lower:
     description: >-
       `Generator-com-ext-p-lower` — a committed extendable unit outputs at
       least its minimum of the chosen build; off, the big M releases the row
     dims: [scenario, snapshot, generator]
-    where: Generator_committable AND Generator_p_nom_extendable AND NOT (Generator_p_nom_mod > 0) AND Generator_active
+    where: Generator_com_ext
     expression: >-
       Generator_p >=
       Generator_p_min_pu * (Generator_p_nom_ext - Generator_maintenance_pu * Generator_maintenance_capacity)
@@ -2809,23 +2920,21 @@ constraints:
       negative, output is also plainly non-negative, a row the big-M lower
       cannot assert while the unit is off
     dims: [scenario, snapshot, generator]
-    where: >-
-      Generator_committable AND Generator_p_nom_extendable
-      AND Generator_p_min_pu_nonneg AND NOT (Generator_p_nom_mod > 0) AND Generator_active
+    where: Generator_com_ext AND Generator_p_min_pu_nonneg
     expression: Generator_p >= 0
   Generator_com_mod_p_lower:
     description: >-
       `Generator-com-mod-p-lower` — a committed modular unit outputs at least
       its minimum of one module, whether the build is fixed or a decision
     dims: [scenario, snapshot, generator]
-    where: Generator_committable AND Generator_p_nom_mod > 0 AND Generator_active
+    where: Generator_committed AND Generator_p_nom_mod > 0
     expression: Generator_p >= Generator_p_min_pu * Generator_p_nom_mod * (Generator_status - Generator_maintenance_pu * Generator_maintenance_status)
   Generator_com_mod_p_upper:
     description: >-
       `Generator-com-mod-p-upper` — a committed modular unit outputs at most
       one module's share, whether the build is fixed or a decision
     dims: [scenario, snapshot, generator]
-    where: Generator_committable AND Generator_p_nom_mod > 0 AND Generator_active
+    where: Generator_committed AND Generator_p_nom_mod > 0
     expression: Generator_p <= Generator_p_max_pu * Generator_p_nom_mod * (Generator_status - Generator_maintenance_pu * Generator_maintenance_status)
   Generator_status_p_fixed_upper:
     description: >-
@@ -2833,7 +2942,7 @@ constraints:
       place, an explicit row as PyPSA writes it: one where the build is not
       modular, and the fixed build's whole count of modules where it is
     dims: [scenario, snapshot, generator]
-    where: Generator_committable AND NOT (Generator_p_nom_extendable AND Generator_p_nom_mod > 0) AND Generator_active
+    where: Generator_committed AND NOT (Generator_p_nom_extendable AND Generator_p_nom_mod > 0)
     expression: Generator_status <= Generator_modules_installed
   Generator_start_up_p_fixed_upper:
     description: >-
@@ -2841,7 +2950,7 @@ constraints:
       place, an explicit row as PyPSA writes it: one where the build is not
       modular, and the fixed build's whole count of modules where it is
     dims: [scenario, snapshot, generator]
-    where: Generator_committable AND NOT (Generator_p_nom_extendable AND Generator_p_nom_mod > 0) AND Generator_active
+    where: Generator_committed AND NOT (Generator_p_nom_extendable AND Generator_p_nom_mod > 0)
     expression: Generator_start_up <= Generator_modules_installed
   Generator_shut_down_p_fixed_upper:
     description: >-
@@ -2849,22 +2958,22 @@ constraints:
       place, an explicit row as PyPSA writes it: one where the build is not
       modular, and the fixed build's whole count of modules where it is
     dims: [scenario, snapshot, generator]
-    where: Generator_committable AND NOT (Generator_p_nom_extendable AND Generator_p_nom_mod > 0) AND Generator_active
+    where: Generator_committed AND NOT (Generator_p_nom_extendable AND Generator_p_nom_mod > 0)
     expression: Generator_shut_down <= Generator_modules_installed
   Generator_status_p_nom_variable_upper:
     description: "`Generator-status-p_nom-variable-upper` — a modular unit is on only where a module is built"
     dims: [scenario, snapshot, generator]
-    where: Generator_committable AND Generator_p_nom_extendable AND Generator_p_nom_mod > 0 AND Generator_active
+    where: Generator_committed AND Generator_p_nom_extendable AND Generator_p_nom_mod > 0
     expression: Generator_status <= Generator_n_mod
   Generator_start_up_p_nom_variable_upper:
     description: "`Generator-start_up-p_nom-variable-upper` — a modular unit starts only where a module is built"
     dims: [scenario, snapshot, generator]
-    where: Generator_committable AND Generator_p_nom_extendable AND Generator_p_nom_mod > 0 AND Generator_active
+    where: Generator_committed AND Generator_p_nom_extendable AND Generator_p_nom_mod > 0
     expression: Generator_start_up <= Generator_n_mod
   Generator_shut_down_p_nom_variable_upper:
     description: "`Generator-shut_down-p_nom-variable-upper` — a modular unit stops only where a module is built"
     dims: [scenario, snapshot, generator]
-    where: Generator_committable AND Generator_p_nom_extendable AND Generator_p_nom_mod > 0 AND Generator_active
+    where: Generator_committed AND Generator_p_nom_extendable AND Generator_p_nom_mod > 0
     expression: Generator_shut_down <= Generator_n_mod
   Generator_maint_event_count:
     description: "`Generator-maint-event-count` — a maintainable generator holds its number of maintenance events over the horizon"
@@ -2889,74 +2998,74 @@ constraints:
       `Generator-maintcap_upper` — the build taken off is at most the chosen build in
       maintenance, and at most the build less its floor out of it
     dims: [scenario, snapshot, generator]
-    where: Generator_maintainable AND Generator_p_nom_extendable AND NOT (Generator_committable AND Generator_p_nom_mod > 0) AND Generator_active
+    where: Generator_maint_ext
     expression: Generator_maintenance_capacity <= Generator_p_nom_ext - Generator_p_nom_min * (1 - Generator_maintenance)
   Generator_maintcap_upper_nommax:
     description: "`Generator-maintcap_upper_nommax` — out of maintenance, no build is taken off"
     dims: [scenario, snapshot, generator]
-    where: Generator_maintainable AND Generator_p_nom_extendable AND NOT (Generator_committable AND Generator_p_nom_mod > 0) AND Generator_active
+    where: Generator_maint_ext
     expression: Generator_maintenance_capacity <= Generator_p_nom_max * Generator_maintenance
   Generator_maintcap_lower_nommax:
     description: "`Generator-maintcap_lower_nommax` — in maintenance, the whole chosen build is taken off"
     dims: [scenario, snapshot, generator]
-    where: Generator_maintainable AND Generator_p_nom_extendable AND NOT (Generator_committable AND Generator_p_nom_mod > 0) AND Generator_active
+    where: Generator_maint_ext
     expression: Generator_maintenance_capacity >= Generator_p_nom_ext - Generator_p_nom_max * (1 - Generator_maintenance)
   Generator_maintcap_lower_nommin:
     description: "`Generator-maintcap_lower_nommin` — in maintenance, at least the floor of the build is taken off"
     dims: [scenario, snapshot, generator]
-    where: Generator_maintainable AND Generator_p_nom_extendable AND NOT (Generator_committable AND Generator_p_nom_mod > 0) AND Generator_active AND Generator_p_nom_min > 0
+    where: Generator_maint_ext AND Generator_p_nom_min > 0
     expression: Generator_maintenance_capacity >= Generator_p_nom_min * Generator_maintenance
   Generator_maint_status_le_status:
     description: "`Generator-maint-status-le-status` — the status in maintenance is at most the status"
     dims: [scenario, snapshot, generator]
-    where: Generator_maintainable AND Generator_committable AND NOT Generator_p_nom_extendable AND NOT (Generator_p_nom_mod > 0) AND Generator_active
+    where: Generator_maintainable AND Generator_committed AND NOT Generator_p_nom_extendable AND NOT (Generator_p_nom_mod > 0)
     expression: Generator_maintenance_status <= Generator_status
   Generator_maint_status_le_maint:
     description: "`Generator-maint-status-le-maint` — out of maintenance, the status in maintenance is zero"
     dims: [scenario, snapshot, generator]
-    where: Generator_maintainable AND Generator_committable AND NOT Generator_p_nom_extendable AND NOT (Generator_p_nom_mod > 0) AND Generator_active
+    where: Generator_maintainable AND Generator_committed AND NOT Generator_p_nom_extendable AND NOT (Generator_p_nom_mod > 0)
     expression: Generator_maintenance_status <= Generator_maintenance
   Generator_maint_status_lb:
     description: "`Generator-maint-status-lb` — on and in maintenance, the status in maintenance is one"
     dims: [scenario, snapshot, generator]
-    where: Generator_maintainable AND Generator_committable AND NOT Generator_p_nom_extendable AND NOT (Generator_p_nom_mod > 0) AND Generator_active
+    where: Generator_maintainable AND Generator_committed AND NOT Generator_p_nom_extendable AND NOT (Generator_p_nom_mod > 0)
     expression: Generator_maintenance_status >= Generator_status + Generator_maintenance - 1
   Generator_maint_modstatus_le_status:
     description: "`Generator-maint-modstatus-le-status` — the modules on in maintenance are at most the modules on"
     dims: [scenario, snapshot, generator]
-    where: Generator_maintainable AND Generator_committable AND Generator_p_nom_mod > 0 AND Generator_active
+    where: Generator_maintainable AND Generator_committed AND Generator_p_nom_mod > 0
     expression: Generator_maintenance_status <= Generator_status
   Generator_maint_modstatus_le_maint:
     description: >-
       `Generator-maint-modstatus-le-maint` — out of maintenance, no module is on in
       maintenance; in it, at most the modules the build cap holds
     dims: [scenario, snapshot, generator]
-    where: Generator_maintainable AND Generator_committable AND Generator_p_nom_mod > 0 AND Generator_active
+    where: Generator_maintainable AND Generator_committed AND Generator_p_nom_mod > 0
     expression: Generator_maintenance_status <= Generator_p_nom_max / Generator_p_nom_mod * Generator_maintenance
   Generator_maint_modstatus_lb:
     description: "`Generator-maint-modstatus-lb` — in maintenance, every module on is on in maintenance"
     dims: [scenario, snapshot, generator]
-    where: Generator_maintainable AND Generator_committable AND Generator_p_nom_mod > 0 AND Generator_active
+    where: Generator_maintainable AND Generator_committed AND Generator_p_nom_mod > 0
     expression: Generator_maintenance_status >= Generator_status - Generator_p_nom_max / Generator_p_nom_mod * (1 - Generator_maintenance)
   Link_com_p_lower:
     description: "`Link-com-p-lower` — a committed link flows at least its minimum; off, at least nothing"
     dims: [scenario, snapshot, link]
-    where: Link_committable AND not Link_p_nom_extendable AND NOT (Link_p_nom_mod > 0) AND Link_active
+    where: Link_committed AND NOT Link_p_nom_extendable AND NOT (Link_p_nom_mod > 0)
     expression: Link_p >= Link_p_min_pu * Link_p_nom * (Link_status - Link_maintenance_pu * Link_maintenance_status)
   Link_com_p_upper:
     description: "`Link-com-p-upper` — a committed link flows at most what is available; off, at most nothing"
     dims: [scenario, snapshot, link]
-    where: Link_committable AND not Link_p_nom_extendable AND NOT (Link_p_nom_mod > 0) AND Link_active
+    where: Link_committed AND NOT Link_p_nom_extendable AND NOT (Link_p_nom_mod > 0)
     expression: Link_p <= Link_p_max_pu * Link_p_nom * (Link_status - Link_maintenance_pu * Link_maintenance_status)
   Link_com_transition_start_up:
     description: "`Link-com-transition-start-up` — turning on is a start, counted against the state the link carried into the snapshot"
     dims: [scenario, snapshot, link]
-    where: Link_committable AND Link_active
+    where: Link_committed
     expression: Link_start_up >= Link_status - Link_previous_status
   Link_com_transition_shut_down:
     description: "`Link-com-transition-shut-down` — turning off is a stop, counted against the state the link carried into the snapshot"
     dims: [scenario, snapshot, link]
-    where: Link_committable AND Link_active
+    where: Link_committed
     expression: Link_shut_down >= Link_previous_status - Link_status
   Link_com_up_time:
     description: >-
@@ -2964,7 +3073,7 @@ constraints:
       is still on. The first snapshot's share of the window is the brought-in
       up time's, which the must-stay-up mask carries
     dims: [scenario, snapshot, link]
-    where: Link_committable AND Link_min_up_time > 0 AND position(snapshot) > 0 AND Link_active
+    where: Link_committed AND Link_min_up_time > 0 AND position(snapshot) > 0
     expression: sum_back(Link_start_up, along=snapshot, window=Link_min_up_time) <= Link_status
   Link_com_down_time:
     description: >-
@@ -2972,19 +3081,19 @@ constraints:
       time is still off. The first snapshot's share of the window is the
       brought-in down time's, which the must-stay-down mask carries
     dims: [scenario, snapshot, link]
-    where: Link_committable AND Link_min_down_time > 0 AND position(snapshot) > 0 AND Link_active
+    where: Link_committed AND Link_min_down_time > 0 AND position(snapshot) > 0
     expression: sum_back(Link_shut_down, along=snapshot, window=Link_min_down_time) <= 1 - Link_status
   Link_com_status_must_stay_up:
     description: "`Link-com-status-min_up_time_must_stay_up` — a link still serving the up time it brought in stays on"
     dims: [scenario, snapshot, link]
-    where: Link_committable AND Link_must_stay_up AND Link_active
+    where: Link_committed AND Link_must_stay_up
     expression: Link_status == 1
   Link_com_status_must_stay_down:
     description: >-
       `Link-com-status-min_down_time_must_stay_up` — a link still serving
       the down time it brought in stays off; PyPSA names the row `_must_stay_up`
     dims: [scenario, snapshot, link]
-    where: Link_committable AND Link_must_stay_down AND Link_active
+    where: Link_committed AND Link_must_stay_down
     expression: Link_status == 0
   Link_p_ramp_limit_up_run_big_m:
     description: >-
@@ -2992,11 +3101,7 @@ constraints:
       raises flow no faster than its limit of the chosen build; the big M
       releases the row in the snapshot it turns on
     dims: [scenario, snapshot, link]
-    where: >-
-      Link_committable AND Link_p_nom_extendable AND NOT (Link_p_nom_mod > 0)
-      AND (Link_ramp_limit_up OR Link_ramp_limit_start_up)
-      AND (position(snapshot, within=snapshot_period[period]) > 0 OR (position(snapshot) == 0 AND (Link_status_initial == 0 OR Link_p_init)))
-      AND Link_active
+    where: Link_com_ext AND (Link_ramp_limit_up OR Link_ramp_limit_start_up) AND Link_ramps_from_previous
     expression: >-
       Link_p - Link_previous_p <=
       Link_ramp_up_rate * Link_p_nom_ext
@@ -3007,11 +3112,7 @@ constraints:
       committed extendable link ramps no further than its start-up ramp of
       the chosen build; the big M releases the row everywhere else
     dims: [scenario, snapshot, link]
-    where: >-
-      Link_committable AND Link_p_nom_extendable AND NOT (Link_p_nom_mod > 0)
-      AND (Link_ramp_limit_up OR Link_ramp_limit_start_up)
-      AND (position(snapshot, within=snapshot_period[period]) > 0 OR (position(snapshot) == 0 AND (Link_status_initial == 0 OR Link_p_init)))
-      AND Link_active
+    where: Link_com_ext AND (Link_ramp_limit_up OR Link_ramp_limit_start_up) AND Link_ramps_from_previous
     expression: >-
       Link_p - Link_previous_p <=
       Link_start_up_rate * Link_p_nom_ext
@@ -3022,11 +3123,7 @@ constraints:
       lowers flow no faster than its limit of the chosen build; the big M
       releases the row in the snapshot it turns off
     dims: [scenario, snapshot, link]
-    where: >-
-      Link_committable AND Link_p_nom_extendable AND NOT (Link_p_nom_mod > 0)
-      AND (Link_ramp_limit_down OR Link_ramp_limit_shut_down)
-      AND (position(snapshot, within=snapshot_period[period]) > 0 OR (position(snapshot) == 0 AND (Link_status_initial == 0 OR Link_p_init)))
-      AND Link_active
+    where: Link_com_ext AND (Link_ramp_limit_down OR Link_ramp_limit_shut_down) AND Link_ramps_from_previous
     expression: >-
       Link_previous_p - Link_p <=
       Link_ramp_down_rate * Link_p_nom_ext
@@ -3037,11 +3134,7 @@ constraints:
       a committed extendable link ramps no further than its shut-down ramp of
       the chosen build; the big M releases the row everywhere else
     dims: [scenario, snapshot, link]
-    where: >-
-      Link_committable AND Link_p_nom_extendable AND NOT (Link_p_nom_mod > 0)
-      AND (Link_ramp_limit_down OR Link_ramp_limit_shut_down)
-      AND (position(snapshot, within=snapshot_period[period]) > 0 OR (position(snapshot) == 0 AND (Link_status_initial == 0 OR Link_p_init)))
-      AND Link_active
+    where: Link_com_ext AND (Link_ramp_limit_down OR Link_ramp_limit_shut_down) AND Link_ramps_from_previous
     expression: >-
       Link_previous_p - Link_p <=
       Link_shut_down_rate * Link_p_nom_ext
@@ -3056,19 +3149,19 @@ constraints:
       `Link-com-ext-p-upper-cap` — a committed extendable link flows
       at most what is available of the chosen build, whatever its status
     dims: [scenario, snapshot, link]
-    where: Link_committable AND Link_p_nom_extendable AND NOT (Link_p_nom_mod > 0) AND Link_active
+    where: Link_com_ext
     expression: Link_p <= Link_p_max_pu * (Link_p_nom_ext - Link_maintenance_pu * Link_maintenance_capacity)
   Link_com_ext_p_upper_big_m:
     description: "`Link-com-ext-p-upper-bigM` — off, a link flows nothing; on, the big M is no bound"
     dims: [scenario, snapshot, link]
-    where: Link_committable AND Link_p_nom_extendable AND NOT (Link_p_nom_mod > 0) AND Link_active
+    where: Link_com_ext
     expression: Link_p <= Link_big_m * Link_status
   Link_com_ext_p_lower:
     description: >-
       `Link-com-ext-p-lower` — a committed extendable link flows at
       least its minimum of the chosen build; off, the big M releases the row
     dims: [scenario, snapshot, link]
-    where: Link_committable AND Link_p_nom_extendable AND NOT (Link_p_nom_mod > 0) AND Link_active
+    where: Link_com_ext
     expression: >-
       Link_p >=
       Link_p_min_pu * (Link_p_nom_ext - Link_maintenance_pu * Link_maintenance_capacity)
@@ -3079,23 +3172,21 @@ constraints:
       negative, flow is also plainly non-negative, a row the big-M lower
       cannot assert while the link is off
     dims: [scenario, snapshot, link]
-    where: >-
-      Link_committable AND Link_p_nom_extendable
-      AND Link_p_min_pu_nonneg AND NOT (Link_p_nom_mod > 0) AND Link_active
+    where: Link_com_ext AND Link_p_min_pu_nonneg
     expression: Link_p >= 0
   Link_com_mod_p_lower:
     description: >-
       `Link-com-mod-p-lower` — a committed modular link flows at least
       its minimum of one module, whether the build is fixed or a decision
     dims: [scenario, snapshot, link]
-    where: Link_committable AND Link_p_nom_mod > 0 AND Link_active
+    where: Link_committed AND Link_p_nom_mod > 0
     expression: Link_p >= Link_p_min_pu * Link_p_nom_mod * (Link_status - Link_maintenance_pu * Link_maintenance_status)
   Link_com_mod_p_upper:
     description: >-
       `Link-com-mod-p-upper` — a committed modular link flows at most
       one module's share, whether the build is fixed or a decision
     dims: [scenario, snapshot, link]
-    where: Link_committable AND Link_p_nom_mod > 0 AND Link_active
+    where: Link_committed AND Link_p_nom_mod > 0
     expression: Link_p <= Link_p_max_pu * Link_p_nom_mod * (Link_status - Link_maintenance_pu * Link_maintenance_status)
   Link_status_p_fixed_upper:
     description: >-
@@ -3103,7 +3194,7 @@ constraints:
       place, an explicit row as PyPSA writes it: one where the build is not
       modular, and the fixed build's whole count of modules where it is
     dims: [scenario, snapshot, link]
-    where: Link_committable AND NOT (Link_p_nom_extendable AND Link_p_nom_mod > 0) AND Link_active
+    where: Link_committed AND NOT (Link_p_nom_extendable AND Link_p_nom_mod > 0)
     expression: Link_status <= Link_modules_installed
   Link_start_up_p_fixed_upper:
     description: >-
@@ -3111,7 +3202,7 @@ constraints:
       place, an explicit row as PyPSA writes it: one where the build is not
       modular, and the fixed build's whole count of modules where it is
     dims: [scenario, snapshot, link]
-    where: Link_committable AND NOT (Link_p_nom_extendable AND Link_p_nom_mod > 0) AND Link_active
+    where: Link_committed AND NOT (Link_p_nom_extendable AND Link_p_nom_mod > 0)
     expression: Link_start_up <= Link_modules_installed
   Link_shut_down_p_fixed_upper:
     description: >-
@@ -3119,22 +3210,22 @@ constraints:
       place, an explicit row as PyPSA writes it: one where the build is not
       modular, and the fixed build's whole count of modules where it is
     dims: [scenario, snapshot, link]
-    where: Link_committable AND NOT (Link_p_nom_extendable AND Link_p_nom_mod > 0) AND Link_active
+    where: Link_committed AND NOT (Link_p_nom_extendable AND Link_p_nom_mod > 0)
     expression: Link_shut_down <= Link_modules_installed
   Link_status_p_nom_variable_upper:
     description: "`Link-status-p_nom-variable-upper` — a modular link is on only where a module is built"
     dims: [scenario, snapshot, link]
-    where: Link_committable AND Link_p_nom_extendable AND Link_p_nom_mod > 0 AND Link_active
+    where: Link_committed AND Link_p_nom_extendable AND Link_p_nom_mod > 0
     expression: Link_status <= Link_n_mod
   Link_start_up_p_nom_variable_upper:
     description: "`Link-start_up-p_nom-variable-upper` — a modular link starts only where a module is built"
     dims: [scenario, snapshot, link]
-    where: Link_committable AND Link_p_nom_extendable AND Link_p_nom_mod > 0 AND Link_active
+    where: Link_committed AND Link_p_nom_extendable AND Link_p_nom_mod > 0
     expression: Link_start_up <= Link_n_mod
   Link_shut_down_p_nom_variable_upper:
     description: "`Link-shut_down-p_nom-variable-upper` — a modular link stops only where a module is built"
     dims: [scenario, snapshot, link]
-    where: Link_committable AND Link_p_nom_extendable AND Link_p_nom_mod > 0 AND Link_active
+    where: Link_committed AND Link_p_nom_extendable AND Link_p_nom_mod > 0
     expression: Link_shut_down <= Link_n_mod
   Link_maint_event_count:
     description: "`Link-maint-event-count` — a maintainable link holds its number of maintenance events over the horizon"
@@ -3159,74 +3250,74 @@ constraints:
       `Link-maintcap_upper` — the build taken off is at most the chosen build in
       maintenance, and at most the build less its floor out of it
     dims: [scenario, snapshot, link]
-    where: Link_maintainable AND Link_p_nom_extendable AND NOT (Link_committable AND Link_p_nom_mod > 0) AND Link_active
+    where: Link_maint_ext
     expression: Link_maintenance_capacity <= Link_p_nom_ext - Link_p_nom_min * (1 - Link_maintenance)
   Link_maintcap_upper_nommax:
     description: "`Link-maintcap_upper_nommax` — out of maintenance, no build is taken off"
     dims: [scenario, snapshot, link]
-    where: Link_maintainable AND Link_p_nom_extendable AND NOT (Link_committable AND Link_p_nom_mod > 0) AND Link_active
+    where: Link_maint_ext
     expression: Link_maintenance_capacity <= Link_p_nom_max * Link_maintenance
   Link_maintcap_lower_nommax:
     description: "`Link-maintcap_lower_nommax` — in maintenance, the whole chosen build is taken off"
     dims: [scenario, snapshot, link]
-    where: Link_maintainable AND Link_p_nom_extendable AND NOT (Link_committable AND Link_p_nom_mod > 0) AND Link_active
+    where: Link_maint_ext
     expression: Link_maintenance_capacity >= Link_p_nom_ext - Link_p_nom_max * (1 - Link_maintenance)
   Link_maintcap_lower_nommin:
     description: "`Link-maintcap_lower_nommin` — in maintenance, at least the floor of the build is taken off"
     dims: [scenario, snapshot, link]
-    where: Link_maintainable AND Link_p_nom_extendable AND NOT (Link_committable AND Link_p_nom_mod > 0) AND Link_active AND Link_p_nom_min > 0
+    where: Link_maint_ext AND Link_p_nom_min > 0
     expression: Link_maintenance_capacity >= Link_p_nom_min * Link_maintenance
   Link_maint_status_le_status:
     description: "`Link-maint-status-le-status` — the status in maintenance is at most the status"
     dims: [scenario, snapshot, link]
-    where: Link_maintainable AND Link_committable AND NOT Link_p_nom_extendable AND NOT (Link_p_nom_mod > 0) AND Link_active
+    where: Link_maintainable AND Link_committed AND NOT Link_p_nom_extendable AND NOT (Link_p_nom_mod > 0)
     expression: Link_maintenance_status <= Link_status
   Link_maint_status_le_maint:
     description: "`Link-maint-status-le-maint` — out of maintenance, the status in maintenance is zero"
     dims: [scenario, snapshot, link]
-    where: Link_maintainable AND Link_committable AND NOT Link_p_nom_extendable AND NOT (Link_p_nom_mod > 0) AND Link_active
+    where: Link_maintainable AND Link_committed AND NOT Link_p_nom_extendable AND NOT (Link_p_nom_mod > 0)
     expression: Link_maintenance_status <= Link_maintenance
   Link_maint_status_lb:
     description: "`Link-maint-status-lb` — on and in maintenance, the status in maintenance is one"
     dims: [scenario, snapshot, link]
-    where: Link_maintainable AND Link_committable AND NOT Link_p_nom_extendable AND NOT (Link_p_nom_mod > 0) AND Link_active
+    where: Link_maintainable AND Link_committed AND NOT Link_p_nom_extendable AND NOT (Link_p_nom_mod > 0)
     expression: Link_maintenance_status >= Link_status + Link_maintenance - 1
   Link_maint_modstatus_le_status:
     description: "`Link-maint-modstatus-le-status` — the modules on in maintenance are at most the modules on"
     dims: [scenario, snapshot, link]
-    where: Link_maintainable AND Link_committable AND Link_p_nom_mod > 0 AND Link_active
+    where: Link_maintainable AND Link_committed AND Link_p_nom_mod > 0
     expression: Link_maintenance_status <= Link_status
   Link_maint_modstatus_le_maint:
     description: >-
       `Link-maint-modstatus-le-maint` — out of maintenance, no module is on in
       maintenance; in it, at most the modules the build cap holds
     dims: [scenario, snapshot, link]
-    where: Link_maintainable AND Link_committable AND Link_p_nom_mod > 0 AND Link_active
+    where: Link_maintainable AND Link_committed AND Link_p_nom_mod > 0
     expression: Link_maintenance_status <= Link_p_nom_max / Link_p_nom_mod * Link_maintenance
   Link_maint_modstatus_lb:
     description: "`Link-maint-modstatus-lb` — in maintenance, every module on is on in maintenance"
     dims: [scenario, snapshot, link]
-    where: Link_maintainable AND Link_committable AND Link_p_nom_mod > 0 AND Link_active
+    where: Link_maintainable AND Link_committed AND Link_p_nom_mod > 0
     expression: Link_maintenance_status >= Link_status - Link_p_nom_max / Link_p_nom_mod * (1 - Link_maintenance)
   Process_com_p_lower:
     description: "`Process-com-p-lower` — a committed process runs at least its minimum; off, at least nothing"
     dims: [scenario, snapshot, process]
-    where: Process_committable AND not Process_p_nom_extendable AND NOT (Process_p_nom_mod > 0) AND Process_active
+    where: Process_committed AND NOT Process_p_nom_extendable AND NOT (Process_p_nom_mod > 0)
     expression: Process_p >= Process_p_min_pu * Process_p_nom * (Process_status - Process_maintenance_pu * Process_maintenance_status)
   Process_com_p_upper:
     description: "`Process-com-p-upper` — a committed process runs at most what is available; off, at most nothing"
     dims: [scenario, snapshot, process]
-    where: Process_committable AND not Process_p_nom_extendable AND NOT (Process_p_nom_mod > 0) AND Process_active
+    where: Process_committed AND NOT Process_p_nom_extendable AND NOT (Process_p_nom_mod > 0)
     expression: Process_p <= Process_p_max_pu * Process_p_nom * (Process_status - Process_maintenance_pu * Process_maintenance_status)
   Process_com_transition_start_up:
     description: "`Process-com-transition-start-up` — turning on is a start, counted against the state the process carried into the snapshot"
     dims: [scenario, snapshot, process]
-    where: Process_committable AND Process_active
+    where: Process_committed
     expression: Process_start_up >= Process_status - Process_previous_status
   Process_com_transition_shut_down:
     description: "`Process-com-transition-shut-down` — turning off is a stop, counted against the state the process carried into the snapshot"
     dims: [scenario, snapshot, process]
-    where: Process_committable AND Process_active
+    where: Process_committed
     expression: Process_shut_down >= Process_previous_status - Process_status
   Process_com_up_time:
     description: >-
@@ -3234,7 +3325,7 @@ constraints:
       is still on. The first snapshot's share of the window is the brought-in
       up time's, which the must-stay-up mask carries
     dims: [scenario, snapshot, process]
-    where: Process_committable AND Process_min_up_time > 0 AND position(snapshot) > 0 AND Process_active
+    where: Process_committed AND Process_min_up_time > 0 AND position(snapshot) > 0
     expression: sum_back(Process_start_up, along=snapshot, window=Process_min_up_time) <= Process_status
   Process_com_down_time:
     description: >-
@@ -3242,19 +3333,19 @@ constraints:
       time is still off. The first snapshot's share of the window is the
       brought-in down time's, which the must-stay-down mask carries
     dims: [scenario, snapshot, process]
-    where: Process_committable AND Process_min_down_time > 0 AND position(snapshot) > 0 AND Process_active
+    where: Process_committed AND Process_min_down_time > 0 AND position(snapshot) > 0
     expression: sum_back(Process_shut_down, along=snapshot, window=Process_min_down_time) <= 1 - Process_status
   Process_com_status_must_stay_up:
     description: "`Process-com-status-min_up_time_must_stay_up` — a process still serving the up time it brought in stays on"
     dims: [scenario, snapshot, process]
-    where: Process_committable AND Process_must_stay_up AND Process_active
+    where: Process_committed AND Process_must_stay_up
     expression: Process_status == 1
   Process_com_status_must_stay_down:
     description: >-
       `Process-com-status-min_down_time_must_stay_up` — a process still serving
       the down time it brought in stays off; PyPSA names the row `_must_stay_up`
     dims: [scenario, snapshot, process]
-    where: Process_committable AND Process_must_stay_down AND Process_active
+    where: Process_committed AND Process_must_stay_down
     expression: Process_status == 0
   Process_p_ramp_limit_up_run_big_m:
     description: >-
@@ -3262,11 +3353,7 @@ constraints:
       raises internal power no faster than its limit of the chosen build; the big M
       releases the row in the snapshot it turns on
     dims: [scenario, snapshot, process]
-    where: >-
-      Process_committable AND Process_p_nom_extendable AND NOT (Process_p_nom_mod > 0)
-      AND (Process_ramp_limit_up OR Process_ramp_limit_start_up)
-      AND (position(snapshot, within=snapshot_period[period]) > 0 OR (position(snapshot) == 0 AND (Process_status_initial == 0 OR Process_p_init)))
-      AND Process_active
+    where: Process_com_ext AND (Process_ramp_limit_up OR Process_ramp_limit_start_up) AND Process_ramps_from_previous
     expression: >-
       Process_p - Process_previous_p <=
       Process_ramp_up_rate * Process_p_nom_ext
@@ -3277,11 +3364,7 @@ constraints:
       committed extendable process ramps no further than its start-up ramp of
       the chosen build; the big M releases the row everywhere else
     dims: [scenario, snapshot, process]
-    where: >-
-      Process_committable AND Process_p_nom_extendable AND NOT (Process_p_nom_mod > 0)
-      AND (Process_ramp_limit_up OR Process_ramp_limit_start_up)
-      AND (position(snapshot, within=snapshot_period[period]) > 0 OR (position(snapshot) == 0 AND (Process_status_initial == 0 OR Process_p_init)))
-      AND Process_active
+    where: Process_com_ext AND (Process_ramp_limit_up OR Process_ramp_limit_start_up) AND Process_ramps_from_previous
     expression: >-
       Process_p - Process_previous_p <=
       Process_start_up_rate * Process_p_nom_ext
@@ -3293,10 +3376,9 @@ constraints:
       releases the row in the snapshot it turns off
     dims: [scenario, snapshot, process]
     where: >-
-      Process_committable AND Process_p_nom_extendable AND NOT (Process_p_nom_mod > 0)
+      Process_com_ext
       AND (Process_ramp_limit_down OR Process_ramp_limit_shut_down)
-      AND (position(snapshot, within=snapshot_period[period]) > 0 OR (position(snapshot) == 0 AND (Process_status_initial == 0 OR Process_p_init)))
-      AND Process_active
+      AND Process_ramps_from_previous
     expression: >-
       Process_previous_p - Process_p <=
       Process_ramp_down_rate * Process_p_nom_ext
@@ -3308,10 +3390,9 @@ constraints:
       the chosen build; the big M releases the row everywhere else
     dims: [scenario, snapshot, process]
     where: >-
-      Process_committable AND Process_p_nom_extendable AND NOT (Process_p_nom_mod > 0)
+      Process_com_ext
       AND (Process_ramp_limit_down OR Process_ramp_limit_shut_down)
-      AND (position(snapshot, within=snapshot_period[period]) > 0 OR (position(snapshot) == 0 AND (Process_status_initial == 0 OR Process_p_init)))
-      AND Process_active
+      AND Process_ramps_from_previous
     expression: >-
       Process_previous_p - Process_p <=
       Process_shut_down_rate * Process_p_nom_ext
@@ -3326,19 +3407,19 @@ constraints:
       `Process-com-ext-p-upper-cap` — a committed extendable process runs
       at most what is available of the chosen build, whatever its status
     dims: [scenario, snapshot, process]
-    where: Process_committable AND Process_p_nom_extendable AND NOT (Process_p_nom_mod > 0) AND Process_active
+    where: Process_com_ext
     expression: Process_p <= Process_p_max_pu * (Process_p_nom_ext - Process_maintenance_pu * Process_maintenance_capacity)
   Process_com_ext_p_upper_big_m:
     description: "`Process-com-ext-p-upper-bigM` — off, a process does not run; on, the big M is no bound"
     dims: [scenario, snapshot, process]
-    where: Process_committable AND Process_p_nom_extendable AND NOT (Process_p_nom_mod > 0) AND Process_active
+    where: Process_com_ext
     expression: Process_p <= Process_big_m * Process_status
   Process_com_ext_p_lower:
     description: >-
       `Process-com-ext-p-lower` — a committed extendable process runs at
       least its minimum of the chosen build; off, the big M releases the row
     dims: [scenario, snapshot, process]
-    where: Process_committable AND Process_p_nom_extendable AND NOT (Process_p_nom_mod > 0) AND Process_active
+    where: Process_com_ext
     expression: >-
       Process_p >=
       Process_p_min_pu * (Process_p_nom_ext - Process_maintenance_pu * Process_maintenance_capacity)
@@ -3349,23 +3430,21 @@ constraints:
       negative, internal power is also plainly non-negative, a row the big-M lower
       cannot assert while the process is off
     dims: [scenario, snapshot, process]
-    where: >-
-      Process_committable AND Process_p_nom_extendable
-      AND Process_p_min_pu_nonneg AND NOT (Process_p_nom_mod > 0) AND Process_active
+    where: Process_com_ext AND Process_p_min_pu_nonneg
     expression: Process_p >= 0
   Process_com_mod_p_lower:
     description: >-
       `Process-com-mod-p-lower` — a committed modular process runs at least
       its minimum of one module, whether the build is fixed or a decision
     dims: [scenario, snapshot, process]
-    where: Process_committable AND Process_p_nom_mod > 0 AND Process_active
+    where: Process_committed AND Process_p_nom_mod > 0
     expression: Process_p >= Process_p_min_pu * Process_p_nom_mod * (Process_status - Process_maintenance_pu * Process_maintenance_status)
   Process_com_mod_p_upper:
     description: >-
       `Process-com-mod-p-upper` — a committed modular process runs at most
       one module's share, whether the build is fixed or a decision
     dims: [scenario, snapshot, process]
-    where: Process_committable AND Process_p_nom_mod > 0 AND Process_active
+    where: Process_committed AND Process_p_nom_mod > 0
     expression: Process_p <= Process_p_max_pu * Process_p_nom_mod * (Process_status - Process_maintenance_pu * Process_maintenance_status)
   Process_status_p_fixed_upper:
     description: >-
@@ -3373,7 +3452,7 @@ constraints:
       place, an explicit row as PyPSA writes it: one where the build is not
       modular, and the fixed build's whole count of modules where it is
     dims: [scenario, snapshot, process]
-    where: Process_committable AND NOT (Process_p_nom_extendable AND Process_p_nom_mod > 0) AND Process_active
+    where: Process_committed AND NOT (Process_p_nom_extendable AND Process_p_nom_mod > 0)
     expression: Process_status <= Process_modules_installed
   Process_start_up_p_fixed_upper:
     description: >-
@@ -3381,7 +3460,7 @@ constraints:
       place, an explicit row as PyPSA writes it: one where the build is not
       modular, and the fixed build's whole count of modules where it is
     dims: [scenario, snapshot, process]
-    where: Process_committable AND NOT (Process_p_nom_extendable AND Process_p_nom_mod > 0) AND Process_active
+    where: Process_committed AND NOT (Process_p_nom_extendable AND Process_p_nom_mod > 0)
     expression: Process_start_up <= Process_modules_installed
   Process_shut_down_p_fixed_upper:
     description: >-
@@ -3389,22 +3468,22 @@ constraints:
       place, an explicit row as PyPSA writes it: one where the build is not
       modular, and the fixed build's whole count of modules where it is
     dims: [scenario, snapshot, process]
-    where: Process_committable AND NOT (Process_p_nom_extendable AND Process_p_nom_mod > 0) AND Process_active
+    where: Process_committed AND NOT (Process_p_nom_extendable AND Process_p_nom_mod > 0)
     expression: Process_shut_down <= Process_modules_installed
   Process_status_p_nom_variable_upper:
     description: "`Process-status-p_nom-variable-upper` — a modular process is on only where a module is built"
     dims: [scenario, snapshot, process]
-    where: Process_committable AND Process_p_nom_extendable AND Process_p_nom_mod > 0 AND Process_active
+    where: Process_committed AND Process_p_nom_extendable AND Process_p_nom_mod > 0
     expression: Process_status <= Process_n_mod
   Process_start_up_p_nom_variable_upper:
     description: "`Process-start_up-p_nom-variable-upper` — a modular process starts only where a module is built"
     dims: [scenario, snapshot, process]
-    where: Process_committable AND Process_p_nom_extendable AND Process_p_nom_mod > 0 AND Process_active
+    where: Process_committed AND Process_p_nom_extendable AND Process_p_nom_mod > 0
     expression: Process_start_up <= Process_n_mod
   Process_shut_down_p_nom_variable_upper:
     description: "`Process-shut_down-p_nom-variable-upper` — a modular process stops only where a module is built"
     dims: [scenario, snapshot, process]
-    where: Process_committable AND Process_p_nom_extendable AND Process_p_nom_mod > 0 AND Process_active
+    where: Process_committed AND Process_p_nom_extendable AND Process_p_nom_mod > 0
     expression: Process_shut_down <= Process_n_mod
   Process_maint_event_count:
     description: "`Process-maint-event-count` — a maintainable process holds its number of maintenance events over the horizon"
@@ -3429,54 +3508,54 @@ constraints:
       `Process-maintcap_upper` — the build taken off is at most the chosen build in
       maintenance, and at most the build less its floor out of it
     dims: [scenario, snapshot, process]
-    where: Process_maintainable AND Process_p_nom_extendable AND NOT (Process_committable AND Process_p_nom_mod > 0) AND Process_active
+    where: Process_maint_ext
     expression: Process_maintenance_capacity <= Process_p_nom_ext - Process_p_nom_min * (1 - Process_maintenance)
   Process_maintcap_upper_nommax:
     description: "`Process-maintcap_upper_nommax` — out of maintenance, no build is taken off"
     dims: [scenario, snapshot, process]
-    where: Process_maintainable AND Process_p_nom_extendable AND NOT (Process_committable AND Process_p_nom_mod > 0) AND Process_active
+    where: Process_maint_ext
     expression: Process_maintenance_capacity <= Process_p_nom_max * Process_maintenance
   Process_maintcap_lower_nommax:
     description: "`Process-maintcap_lower_nommax` — in maintenance, the whole chosen build is taken off"
     dims: [scenario, snapshot, process]
-    where: Process_maintainable AND Process_p_nom_extendable AND NOT (Process_committable AND Process_p_nom_mod > 0) AND Process_active
+    where: Process_maint_ext
     expression: Process_maintenance_capacity >= Process_p_nom_ext - Process_p_nom_max * (1 - Process_maintenance)
   Process_maintcap_lower_nommin:
     description: "`Process-maintcap_lower_nommin` — in maintenance, at least the floor of the build is taken off"
     dims: [scenario, snapshot, process]
-    where: Process_maintainable AND Process_p_nom_extendable AND NOT (Process_committable AND Process_p_nom_mod > 0) AND Process_active AND Process_p_nom_min > 0
+    where: Process_maint_ext AND Process_p_nom_min > 0
     expression: Process_maintenance_capacity >= Process_p_nom_min * Process_maintenance
   Process_maint_status_le_status:
     description: "`Process-maint-status-le-status` — the status in maintenance is at most the status"
     dims: [scenario, snapshot, process]
-    where: Process_maintainable AND Process_committable AND NOT Process_p_nom_extendable AND NOT (Process_p_nom_mod > 0) AND Process_active
+    where: Process_maintainable AND Process_committed AND NOT Process_p_nom_extendable AND NOT (Process_p_nom_mod > 0)
     expression: Process_maintenance_status <= Process_status
   Process_maint_status_le_maint:
     description: "`Process-maint-status-le-maint` — out of maintenance, the status in maintenance is zero"
     dims: [scenario, snapshot, process]
-    where: Process_maintainable AND Process_committable AND NOT Process_p_nom_extendable AND NOT (Process_p_nom_mod > 0) AND Process_active
+    where: Process_maintainable AND Process_committed AND NOT Process_p_nom_extendable AND NOT (Process_p_nom_mod > 0)
     expression: Process_maintenance_status <= Process_maintenance
   Process_maint_status_lb:
     description: "`Process-maint-status-lb` — on and in maintenance, the status in maintenance is one"
     dims: [scenario, snapshot, process]
-    where: Process_maintainable AND Process_committable AND NOT Process_p_nom_extendable AND NOT (Process_p_nom_mod > 0) AND Process_active
+    where: Process_maintainable AND Process_committed AND NOT Process_p_nom_extendable AND NOT (Process_p_nom_mod > 0)
     expression: Process_maintenance_status >= Process_status + Process_maintenance - 1
   Process_maint_modstatus_le_status:
     description: "`Process-maint-modstatus-le-status` — the modules on in maintenance are at most the modules on"
     dims: [scenario, snapshot, process]
-    where: Process_maintainable AND Process_committable AND Process_p_nom_mod > 0 AND Process_active
+    where: Process_maintainable AND Process_committed AND Process_p_nom_mod > 0
     expression: Process_maintenance_status <= Process_status
   Process_maint_modstatus_le_maint:
     description: >-
       `Process-maint-modstatus-le-maint` — out of maintenance, no module is on in
       maintenance; in it, at most the modules the build cap holds
     dims: [scenario, snapshot, process]
-    where: Process_maintainable AND Process_committable AND Process_p_nom_mod > 0 AND Process_active
+    where: Process_maintainable AND Process_committed AND Process_p_nom_mod > 0
     expression: Process_maintenance_status <= Process_p_nom_max / Process_p_nom_mod * Process_maintenance
   Process_maint_modstatus_lb:
     description: "`Process-maint-modstatus-lb` — in maintenance, every module on is on in maintenance"
     dims: [scenario, snapshot, process]
-    where: Process_maintainable AND Process_committable AND Process_p_nom_mod > 0 AND Process_active
+    where: Process_maintainable AND Process_committed AND Process_p_nom_mod > 0
     expression: Process_maintenance_status >= Process_status - Process_p_nom_max / Process_p_nom_mod * (1 - Process_maintenance)
   Line_fix_s_lower:
     description: "`Line-fix-s-lower` — a fixed line carries at least the negative of its rating, the loss counted against it"
@@ -3541,7 +3620,7 @@ constraints:
   Line_loss_upper:
     description: "`Line-loss_upper` — a line dissipates at most the loss at its rating"
     dims: [scenario, snapshot, line]
-    where: transmission_losses AND Line_active
+    where: Line_lossy
     expression: Line_loss <= Line_loss_max
   Line_loss_tangents_forward:
     description: >-
@@ -3550,14 +3629,14 @@ constraints:
       `k`, or one row stacked over its `secant` axis, and this block states them
       all over the segment dimension
     dims: [scenario, snapshot, line, segment]
-    where: transmission_losses AND Line_active
+    where: Line_lossy
     expression: Line_loss + Line_loss_slope * Line_s >= Line_loss_offset
   Line_loss_tangents_reverse:
     description: >-
       `Line-loss_tangents-{k}--1`, `Line-loss_secants-neg` — the same fan
       mirrored, the loss depending on the flow's magnitude
     dims: [scenario, snapshot, line, segment]
-    where: transmission_losses AND Line_active
+    where: Line_lossy
     expression: Line_loss - Line_loss_slope * Line_s >= Line_loss_offset
   Transformer_fix_s_lower:
     description: "`Transformer-fix-s-lower` — a fixed transformer carries at least the negative of its rating, the loss counted against it"
@@ -3639,7 +3718,7 @@ constraints:
   Transformer_loss_upper:
     description: "`Transformer-loss_upper` — a transformer dissipates at most the loss at its rating"
     dims: [scenario, snapshot, transformer]
-    where: transmission_losses AND Transformer_active
+    where: Transformer_lossy
     expression: Transformer_loss <= Transformer_loss_max
   Transformer_loss_tangents_forward:
     description: >-
@@ -3647,14 +3726,14 @@ constraints:
       loss sits above every cut to its curve for flow one way, as a line's
       does, over the segment dimension
     dims: [scenario, snapshot, transformer, segment]
-    where: transmission_losses AND Transformer_active
+    where: Transformer_lossy
     expression: Transformer_loss + Transformer_loss_slope * Transformer_s >= Transformer_loss_offset
   Transformer_loss_tangents_reverse:
     description: >-
       `Transformer-loss_tangents-{k}--1`, `Transformer-loss_secants-neg` — the
       same fan mirrored, the loss depending on the flow's magnitude
     dims: [scenario, snapshot, transformer, segment]
-    where: transmission_losses AND Transformer_active
+    where: Transformer_lossy
     expression: Transformer_loss - Transformer_loss_slope * Transformer_s >= Transformer_loss_offset
   Line_fix_s_lower_security:
     description: >-
@@ -3775,7 +3854,7 @@ constraints:
     where: >-
       (Generator_ramp_limit_up OR Generator_ramp_limit_start_up)
       AND NOT (Generator_committable AND Generator_p_nom_extendable AND NOT (Generator_p_nom_mod > 0))
-      AND (position(snapshot, within=snapshot_period[period]) > 0 OR (position(snapshot) == 0 AND (Generator_status_initial == 0 OR Generator_p_init)))
+      AND Generator_ramps_from_previous
       AND Generator_active
     expression: Generator_p - Generator_previous_p <= Generator_ramp_up_allowance
   Generator_p_ramp_limit_down:
@@ -3790,7 +3869,7 @@ constraints:
     where: >-
       (Generator_ramp_limit_down OR Generator_ramp_limit_shut_down)
       AND NOT (Generator_committable AND Generator_p_nom_extendable AND NOT (Generator_p_nom_mod > 0))
-      AND (position(snapshot, within=snapshot_period[period]) > 0 OR (position(snapshot) == 0 AND (Generator_status_initial == 0 OR Generator_p_init)))
+      AND Generator_ramps_from_previous
       AND Generator_active
     expression: Generator_previous_p - Generator_p <= Generator_ramp_down_allowance
   Link_p_ramp_limit_up:
@@ -3805,7 +3884,7 @@ constraints:
     where: >-
       (Link_ramp_limit_up OR Link_ramp_limit_start_up)
       AND NOT (Link_committable AND Link_p_nom_extendable AND NOT (Link_p_nom_mod > 0))
-      AND (position(snapshot, within=snapshot_period[period]) > 0 OR (position(snapshot) == 0 AND (Link_status_initial == 0 OR Link_p_init)))
+      AND Link_ramps_from_previous
       AND Link_active
     expression: Link_p - Link_previous_p <= Link_ramp_up_allowance
   Link_p_ramp_limit_down:
@@ -3820,7 +3899,7 @@ constraints:
     where: >-
       (Link_ramp_limit_down OR Link_ramp_limit_shut_down)
       AND NOT (Link_committable AND Link_p_nom_extendable AND NOT (Link_p_nom_mod > 0))
-      AND (position(snapshot, within=snapshot_period[period]) > 0 OR (position(snapshot) == 0 AND (Link_status_initial == 0 OR Link_p_init)))
+      AND Link_ramps_from_previous
       AND Link_active
     expression: Link_previous_p - Link_p <= Link_ramp_down_allowance
   Process_p_ramp_limit_up:
@@ -3835,7 +3914,7 @@ constraints:
     where: >-
       (Process_ramp_limit_up OR Process_ramp_limit_start_up)
       AND NOT (Process_committable AND Process_p_nom_extendable AND NOT (Process_p_nom_mod > 0))
-      AND (position(snapshot, within=snapshot_period[period]) > 0 OR (position(snapshot) == 0 AND (Process_status_initial == 0 OR Process_p_init)))
+      AND Process_ramps_from_previous
       AND Process_active
     expression: Process_p - Process_previous_p <= Process_ramp_up_allowance
   Process_p_ramp_limit_down:
@@ -3850,40 +3929,40 @@ constraints:
     where: >-
       (Process_ramp_limit_down OR Process_ramp_limit_shut_down)
       AND NOT (Process_committable AND Process_p_nom_extendable AND NOT (Process_p_nom_mod > 0))
-      AND (position(snapshot, within=snapshot_period[period]) > 0 OR (position(snapshot) == 0 AND (Process_status_initial == 0 OR Process_p_init)))
+      AND Process_ramps_from_previous
       AND Process_active
     expression: Process_previous_p - Process_p <= Process_ramp_down_allowance
   StorageUnit_ext_p_dispatch_lower:
     description: "`StorageUnit-ext-p_dispatch-lower` — dispatch is non-negative"
     dims: [scenario, snapshot, storage_unit]
-    where: StorageUnit_p_nom_extendable AND StorageUnit_active
+    where: StorageUnit_ext
     expression: StorageUnit_p_dispatch >= 0
   StorageUnit_ext_p_dispatch_upper:
     description: "`StorageUnit-ext-p_dispatch-upper` — an extendable unit dispatches at most the chosen build"
     dims: [scenario, snapshot, storage_unit]
-    where: StorageUnit_p_nom_extendable AND StorageUnit_active
+    where: StorageUnit_ext
     expression: StorageUnit_p_dispatch <= StorageUnit_p_max_pu * StorageUnit_p_nom_ext
   StorageUnit_ext_p_store_lower:
     description: "`StorageUnit-ext-p_store-lower` — storing is non-negative"
     dims: [scenario, snapshot, storage_unit]
-    where: StorageUnit_p_nom_extendable AND StorageUnit_active
+    where: StorageUnit_ext
     expression: StorageUnit_p_store >= 0
   StorageUnit_ext_p_store_upper:
     description: >-
       `StorageUnit-ext-p_store-upper` — an extendable unit stores at most the
       chosen build, the minimum-per-unit column carrying that cap negated
     dims: [scenario, snapshot, storage_unit]
-    where: StorageUnit_p_nom_extendable AND StorageUnit_active
+    where: StorageUnit_ext
     expression: StorageUnit_p_store <= -StorageUnit_p_min_pu * StorageUnit_p_nom_ext
   StorageUnit_ext_state_of_charge_lower:
     description: "`StorageUnit-ext-state_of_charge-lower` — charge is non-negative"
     dims: [scenario, snapshot, storage_unit]
-    where: StorageUnit_p_nom_extendable AND StorageUnit_active
+    where: StorageUnit_ext
     expression: StorageUnit_state_of_charge >= 0
   StorageUnit_ext_state_of_charge_upper:
     description: "`StorageUnit-ext-state_of_charge-upper` — an extendable unit holds at most its hours at the chosen build"
     dims: [scenario, snapshot, storage_unit]
-    where: StorageUnit_p_nom_extendable AND StorageUnit_active
+    where: StorageUnit_ext
     expression: StorageUnit_state_of_charge <= StorageUnit_max_hours * StorageUnit_p_nom_ext
   StorageUnit_ext_p_nom_lower:
     description: "`StorageUnit-ext-p_nom-lower` — the chosen build is at least its floor in every scenario"
diff --git a/examples/pypsa/generator.yaml b/examples/pypsa/generator.yaml
index f55ccf07..6cd7ca87 100644
--- a/examples/pypsa/generator.yaml
+++ b/examples/pypsa/generator.yaml
@@ -215,6 +215,13 @@ expressions:
     expression: sum(Generator_sign * Generator_p, over=generator, by=Generator_bus[bus])
     adds_to: Bus_injection
 
+masks:
+  Generator_committed:
+    description: >-
+      a committable generator that stands in the snapshot's period — every
+      unit-commitment row's set
+    where: Generator_committable AND Generator_active
+
 constraints:
   Generator_fix_p_lower:
     description: "`Generator-fix-p-lower` — a fixed generator outputs at least its minimum"
diff --git a/examples/pypsa/generator_commitment.yaml b/examples/pypsa/generator_commitment.yaml
index ab87bf2c..f325c324 100644
--- a/examples/pypsa/generator_commitment.yaml
+++ b/examples/pypsa/generator_commitment.yaml
@@ -81,21 +81,21 @@ variables:
       the rows below cap at one, or at the module count where the build is
       modular
     dims: [scenario, snapshot, generator]
-    where: Generator_committable AND Generator_active
+    where: Generator_committed
     domain: integer
     bounds:
       lower: 0
   Generator_start_up:
     description: "`Generator-start_up` — how much of a committable unit turns on this snapshot, capped as the status is"
     dims: [scenario, snapshot, generator]
-    where: Generator_committable AND Generator_active
+    where: Generator_committed
     domain: integer
     bounds:
       lower: 0
   Generator_shut_down:
     description: "`Generator-shut_down` — how much of a committable unit turns off this snapshot, capped as the status is"
     dims: [scenario, snapshot, generator]
-    where: Generator_committable AND Generator_active
+    where: Generator_committed
     domain: integer
     bounds:
       lower: 0
@@ -121,6 +121,8 @@ given:
     Generator_p_nom_ext: { dims: [generator] }
   expressions:
     scenario_opex: { dims: [scenario] }
+  masks:
+    Generator_committed: { dims: [snapshot, generator] }
 
 expressions:
   Generator_previous_status:
@@ -148,26 +150,38 @@ expressions:
       + sum(sum(Generator_shut_down * Generator_shut_down_cost, over=generator), over=snapshot)
     adds_to: scenario_opex
 
+masks:
+  Generator_com_ext:
+    description: >-
+      a committable generator with an extendable, non-modular build that
+      stands in the snapshot's period — PyPSA's `com-ext` rows, whose status
+      is relaxed against the chosen build
+    where: >-
+      Generator_committable
+      AND Generator_p_nom_extendable
+      AND NOT (Generator_p_nom_mod > 0)
+      AND Generator_active
+
 constraints:
   Generator_com_p_lower:
     description: "`Generator-com-p-lower` — a committed unit outputs at least its minimum; off, at least nothing"
     dims: [scenario, snapshot, generator]
-    where: Generator_committable AND not Generator_p_nom_extendable AND NOT (Generator_p_nom_mod > 0) AND Generator_active
+    where: Generator_committed AND NOT Generator_p_nom_extendable AND NOT (Generator_p_nom_mod > 0)
     expression: Generator_p >= Generator_p_min_pu * Generator_p_nom * (Generator_status - Generator_maintenance_pu * Generator_maintenance_status)
   Generator_com_p_upper:
     description: "`Generator-com-p-upper` — a committed unit outputs at most what is available; off, at most nothing"
     dims: [scenario, snapshot, generator]
-    where: Generator_committable AND not Generator_p_nom_extendable AND NOT (Generator_p_nom_mod > 0) AND Generator_active
+    where: Generator_committed AND NOT Generator_p_nom_extendable AND NOT (Generator_p_nom_mod > 0)
     expression: Generator_p <= Generator_p_max_pu * Generator_p_nom * (Generator_status - Generator_maintenance_pu * Generator_maintenance_status)
   Generator_com_transition_start_up:
     description: "`Generator-com-transition-start-up` — turning on is a start, counted against the state the unit carried into the snapshot"
     dims: [scenario, snapshot, generator]
-    where: Generator_committable AND Generator_active
+    where: Generator_committed
     expression: Generator_start_up >= Generator_status - Generator_previous_status
   Generator_com_transition_shut_down:
     description: "`Generator-com-transition-shut-down` — turning off is a stop, counted against the state the unit carried into the snapshot"
     dims: [scenario, snapshot, generator]
-    where: Generator_committable AND Generator_active
+    where: Generator_committed
     expression: Generator_shut_down >= Generator_previous_status - Generator_status
   Generator_com_up_time:
     description: >-
@@ -175,7 +189,7 @@ constraints:
       is still on. The first snapshot's share of the window is the brought-in
       up time's, which the must-stay-up mask carries
     dims: [scenario, snapshot, generator]
-    where: Generator_committable AND Generator_min_up_time > 0 AND position(snapshot) > 0 AND Generator_active
+    where: Generator_committed AND Generator_min_up_time > 0 AND position(snapshot) > 0
     expression: sum_back(Generator_start_up, along=snapshot, window=Generator_min_up_time) <= Generator_status
   Generator_com_down_time:
     description: >-
@@ -183,38 +197,38 @@ constraints:
       time is still off. The first snapshot's share of the window is the
       brought-in down time's, which the must-stay-down mask carries
     dims: [scenario, snapshot, generator]
-    where: Generator_committable AND Generator_min_down_time > 0 AND position(snapshot) > 0 AND Generator_active
+    where: Generator_committed AND Generator_min_down_time > 0 AND position(snapshot) > 0
     expression: sum_back(Generator_shut_down, along=snapshot, window=Generator_min_down_time) <= 1 - Generator_status
   Generator_com_status_must_stay_up:
     description: "`Generator-com-status-min_up_time_must_stay_up` — a unit still serving the up time it brought in stays on"
     dims: [scenario, snapshot, generator]
-    where: Generator_committable AND Generator_must_stay_up AND Generator_active
+    where: Generator_committed AND Generator_must_stay_up
     expression: Generator_status == 1
   Generator_com_status_must_stay_down:
     description: >-
       `Generator-com-status-min_down_time_must_stay_up` — a unit still serving
       the down time it brought in stays off; PyPSA names the row `_must_stay_up`
     dims: [scenario, snapshot, generator]
-    where: Generator_committable AND Generator_must_stay_down AND Generator_active
+    where: Generator_committed AND Generator_must_stay_down
     expression: Generator_status == 0
   Generator_com_ext_p_upper_cap:
     description: >-
       `Generator-com-ext-p-upper-cap` — a committed extendable unit outputs
       at most what is available of the chosen build, whatever its status
     dims: [scenario, snapshot, generator]
-    where: Generator_committable AND Generator_p_nom_extendable AND NOT (Generator_p_nom_mod > 0) AND Generator_active
+    where: Generator_com_ext
     expression: Generator_p <= Generator_p_max_pu * (Generator_p_nom_ext - Generator_maintenance_pu * Generator_maintenance_capacity)
   Generator_com_ext_p_upper_big_m:
     description: "`Generator-com-ext-p-upper-bigM` — off, a unit outputs nothing; on, the big M is no bound"
     dims: [scenario, snapshot, generator]
-    where: Generator_committable AND Generator_p_nom_extendable AND NOT (Generator_p_nom_mod > 0) AND Generator_active
+    where: Generator_com_ext
     expression: Generator_p <= Generator_big_m * Generator_status
   Generator_com_ext_p_lower:
     description: >-
       `Generator-com-ext-p-lower` — a committed extendable unit outputs at
       least its minimum of the chosen build; off, the big M releases the row
     dims: [scenario, snapshot, generator]
-    where: Generator_committable AND Generator_p_nom_extendable AND NOT (Generator_p_nom_mod > 0) AND Generator_active
+    where: Generator_com_ext
     expression: >-
       Generator_p >=
       Generator_p_min_pu * (Generator_p_nom_ext - Generator_maintenance_pu * Generator_maintenance_capacity)
@@ -225,23 +239,21 @@ constraints:
       negative, output is also plainly non-negative, a row the big-M lower
       cannot assert while the unit is off
     dims: [scenario, snapshot, generator]
-    where: >-
-      Generator_committable AND Generator_p_nom_extendable
-      AND Generator_p_min_pu_nonneg AND NOT (Generator_p_nom_mod > 0) AND Generator_active
+    where: Generator_com_ext AND Generator_p_min_pu_nonneg
     expression: Generator_p >= 0
   Generator_com_mod_p_lower:
     description: >-
       `Generator-com-mod-p-lower` — a committed modular unit outputs at least
       its minimum of one module, whether the build is fixed or a decision
     dims: [scenario, snapshot, generator]
-    where: Generator_committable AND Generator_p_nom_mod > 0 AND Generator_active
+    where: Generator_committed AND Generator_p_nom_mod > 0
     expression: Generator_p >= Generator_p_min_pu * Generator_p_nom_mod * (Generator_status - Generator_maintenance_pu * Generator_maintenance_status)
   Generator_com_mod_p_upper:
     description: >-
       `Generator-com-mod-p-upper` — a committed modular unit outputs at most
       one module's share, whether the build is fixed or a decision
     dims: [scenario, snapshot, generator]
-    where: Generator_committable AND Generator_p_nom_mod > 0 AND Generator_active
+    where: Generator_committed AND Generator_p_nom_mod > 0
     expression: Generator_p <= Generator_p_max_pu * Generator_p_nom_mod * (Generator_status - Generator_maintenance_pu * Generator_maintenance_status)
   Generator_status_p_fixed_upper:
     description: >-
@@ -249,7 +261,7 @@ constraints:
       place, an explicit row as PyPSA writes it: one where the build is not
       modular, and the fixed build's whole count of modules where it is
     dims: [scenario, snapshot, generator]
-    where: Generator_committable AND NOT (Generator_p_nom_extendable AND Generator_p_nom_mod > 0) AND Generator_active
+    where: Generator_committed AND NOT (Generator_p_nom_extendable AND Generator_p_nom_mod > 0)
     expression: Generator_status <= Generator_modules_installed
   Generator_start_up_p_fixed_upper:
     description: >-
@@ -257,7 +269,7 @@ constraints:
       place, an explicit row as PyPSA writes it: one where the build is not
       modular, and the fixed build's whole count of modules where it is
     dims: [scenario, snapshot, generator]
-    where: Generator_committable AND NOT (Generator_p_nom_extendable AND Generator_p_nom_mod > 0) AND Generator_active
+    where: Generator_committed AND NOT (Generator_p_nom_extendable AND Generator_p_nom_mod > 0)
     expression: Generator_start_up <= Generator_modules_installed
   Generator_shut_down_p_fixed_upper:
     description: >-
@@ -265,20 +277,20 @@ constraints:
       place, an explicit row as PyPSA writes it: one where the build is not
       modular, and the fixed build's whole count of modules where it is
     dims: [scenario, snapshot, generator]
-    where: Generator_committable AND NOT (Generator_p_nom_extendable AND Generator_p_nom_mod > 0) AND Generator_active
+    where: Generator_committed AND NOT (Generator_p_nom_extendable AND Generator_p_nom_mod > 0)
     expression: Generator_shut_down <= Generator_modules_installed
   Generator_status_p_nom_variable_upper:
     description: "`Generator-status-p_nom-variable-upper` — a modular unit is on only where a module is built"
     dims: [scenario, snapshot, generator]
-    where: Generator_committable AND Generator_p_nom_extendable AND Generator_p_nom_mod > 0 AND Generator_active
+    where: Generator_committed AND Generator_p_nom_extendable AND Generator_p_nom_mod > 0
     expression: Generator_status <= Generator_n_mod
   Generator_start_up_p_nom_variable_upper:
     description: "`Generator-start_up-p_nom-variable-upper` — a modular unit starts only where a module is built"
     dims: [scenario, snapshot, generator]
-    where: Generator_committable AND Generator_p_nom_extendable AND Generator_p_nom_mod > 0 AND Generator_active
+    where: Generator_committed AND Generator_p_nom_extendable AND Generator_p_nom_mod > 0
     expression: Generator_start_up <= Generator_n_mod
   Generator_shut_down_p_nom_variable_upper:
     description: "`Generator-shut_down-p_nom-variable-upper` — a modular unit stops only where a module is built"
     dims: [scenario, snapshot, generator]
-    where: Generator_committable AND Generator_p_nom_extendable AND Generator_p_nom_mod > 0 AND Generator_active
+    where: Generator_committed AND Generator_p_nom_extendable AND Generator_p_nom_mod > 0
     expression: Generator_shut_down <= Generator_n_mod
diff --git a/examples/pypsa/generator_maintenance.yaml b/examples/pypsa/generator_maintenance.yaml
index 39721243..c42dd07d 100644
--- a/examples/pypsa/generator_maintenance.yaml
+++ b/examples/pypsa/generator_maintenance.yaml
@@ -75,9 +75,7 @@ variables:
       `Generator-maintenance_capacity` — the chosen build while in maintenance, zero
       otherwise: the product the `maintcap` rows linearize
     dims: [scenario, snapshot, generator]
-    where: >-
-      Generator_maintainable AND Generator_p_nom_extendable
-      AND NOT (Generator_committable AND Generator_p_nom_mod > 0) AND Generator_active
+    where: Generator_maint_ext
     absence: zero
     bounds:
       lower: 0
@@ -88,8 +86,9 @@ variables:
       maintenance may also be off
     dims: [scenario, snapshot, generator]
     where: >-
-      Generator_maintainable AND Generator_committable
-      AND NOT (Generator_p_nom_extendable AND NOT (Generator_p_nom_mod > 0)) AND Generator_active
+      Generator_maintainable
+      AND Generator_committed
+      AND NOT (Generator_p_nom_extendable AND NOT (Generator_p_nom_mod > 0))
     absence: zero
     bounds:
       lower: 0
@@ -106,6 +105,20 @@ given:
   variables:
     Generator_status: { dims: [scenario, snapshot, generator], domain: integer }
     Generator_p_nom_ext: { dims: [generator] }
+  masks:
+    Generator_committed: { dims: [snapshot, generator] }
+
+masks:
+  Generator_maint_ext:
+    description: >-
+      a maintainable generator with an extendable build, unless it is
+      committable and modular, that stands in the snapshot's period — the
+      maintenance rows against the chosen build
+    where: >-
+      Generator_maintainable
+      AND Generator_p_nom_extendable
+      AND NOT (Generator_committable AND Generator_p_nom_mod > 0)
+      AND Generator_active
 
 constraints:
   Generator_maint_event_count:
@@ -131,54 +144,54 @@ constraints:
       `Generator-maintcap_upper` — the build taken off is at most the chosen build in
       maintenance, and at most the build less its floor out of it
     dims: [scenario, snapshot, generator]
-    where: Generator_maintainable AND Generator_p_nom_extendable AND NOT (Generator_committable AND Generator_p_nom_mod > 0) AND Generator_active
+    where: Generator_maint_ext
     expression: Generator_maintenance_capacity <= Generator_p_nom_ext - Generator_p_nom_min * (1 - Generator_maintenance)
   Generator_maintcap_upper_nommax:
     description: "`Generator-maintcap_upper_nommax` — out of maintenance, no build is taken off"
     dims: [scenario, snapshot, generator]
-    where: Generator_maintainable AND Generator_p_nom_extendable AND NOT (Generator_committable AND Generator_p_nom_mod > 0) AND Generator_active
+    where: Generator_maint_ext
     expression: Generator_maintenance_capacity <= Generator_p_nom_max * Generator_maintenance
   Generator_maintcap_lower_nommax:
     description: "`Generator-maintcap_lower_nommax` — in maintenance, the whole chosen build is taken off"
     dims: [scenario, snapshot, generator]
-    where: Generator_maintainable AND Generator_p_nom_extendable AND NOT (Generator_committable AND Generator_p_nom_mod > 0) AND Generator_active
+    where: Generator_maint_ext
     expression: Generator_maintenance_capacity >= Generator_p_nom_ext - Generator_p_nom_max * (1 - Generator_maintenance)
   Generator_maintcap_lower_nommin:
     description: "`Generator-maintcap_lower_nommin` — in maintenance, at least the floor of the build is taken off"
     dims: [scenario, snapshot, generator]
-    where: Generator_maintainable AND Generator_p_nom_extendable AND NOT (Generator_committable AND Generator_p_nom_mod > 0) AND Generator_active AND Generator_p_nom_min > 0
+    where: Generator_maint_ext AND Generator_p_nom_min > 0
     expression: Generator_maintenance_capacity >= Generator_p_nom_min * Generator_maintenance
   Generator_maint_status_le_status:
     description: "`Generator-maint-status-le-status` — the status in maintenance is at most the status"
     dims: [scenario, snapshot, generator]
-    where: Generator_maintainable AND Generator_committable AND NOT Generator_p_nom_extendable AND NOT (Generator_p_nom_mod > 0) AND Generator_active
+    where: Generator_maintainable AND Generator_committed AND NOT Generator_p_nom_extendable AND NOT (Generator_p_nom_mod > 0)
     expression: Generator_maintenance_status <= Generator_status
   Generator_maint_status_le_maint:
     description: "`Generator-maint-status-le-maint` — out of maintenance, the status in maintenance is zero"
     dims: [scenario, snapshot, generator]
-    where: Generator_maintainable AND Generator_committable AND NOT Generator_p_nom_extendable AND NOT (Generator_p_nom_mod > 0) AND Generator_active
+    where: Generator_maintainable AND Generator_committed AND NOT Generator_p_nom_extendable AND NOT (Generator_p_nom_mod > 0)
     expression: Generator_maintenance_status <= Generator_maintenance
   Generator_maint_status_lb:
     description: "`Generator-maint-status-lb` — on and in maintenance, the status in maintenance is one"
     dims: [scenario, snapshot, generator]
-    where: Generator_maintainable AND Generator_committable AND NOT Generator_p_nom_extendable AND NOT (Generator_p_nom_mod > 0) AND Generator_active
+    where: Generator_maintainable AND Generator_committed AND NOT Generator_p_nom_extendable AND NOT (Generator_p_nom_mod > 0)
     expression: Generator_maintenance_status >= Generator_status + Generator_maintenance - 1
   Generator_maint_modstatus_le_status:
     description: "`Generator-maint-modstatus-le-status` — the modules on in maintenance are at most the modules on"
     dims: [scenario, snapshot, generator]
-    where: Generator_maintainable AND Generator_committable AND Generator_p_nom_mod > 0 AND Generator_active
+    where: Generator_maintainable AND Generator_committed AND Generator_p_nom_mod > 0
     expression: Generator_maintenance_status <= Generator_status
   Generator_maint_modstatus_le_maint:
     description: >-
       `Generator-maint-modstatus-le-maint` — out of maintenance, no module is on in
       maintenance; in it, at most the modules the build cap holds
     dims: [scenario, snapshot, generator]
-    where: Generator_maintainable AND Generator_committable AND Generator_p_nom_mod > 0 AND Generator_active
+    where: Generator_maintainable AND Generator_committed AND Generator_p_nom_mod > 0
     expression: Generator_maintenance_status <= Generator_p_nom_max / Generator_p_nom_mod * Generator_maintenance
   Generator_maint_modstatus_lb:
     description: "`Generator-maint-modstatus-lb` — in maintenance, every module on is on in maintenance"
     dims: [scenario, snapshot, generator]
-    where: Generator_maintainable AND Generator_committable AND Generator_p_nom_mod > 0 AND Generator_active
+    where: Generator_maintainable AND Generator_committed AND Generator_p_nom_mod > 0
     expression: Generator_maintenance_status >= Generator_status - Generator_p_nom_max / Generator_p_nom_mod * (1 - Generator_maintenance)
 
 assumptions:
diff --git a/examples/pypsa/generator_ramping.yaml b/examples/pypsa/generator_ramping.yaml
index 86453e53..6f021f28 100644
--- a/examples/pypsa/generator_ramping.yaml
+++ b/examples/pypsa/generator_ramping.yaml
@@ -60,6 +60,8 @@ given:
     Generator_previous_status: { dims: [scenario, snapshot, generator] }
     Generator_p_nom_effective: { dims: [scenario, generator] }
     Generator_p_nom_committed: { dims: [scenario, generator] }
+  masks:
+    Generator_com_ext: { dims: [snapshot, generator] }
 
 expressions:
   Generator_previous_p:
@@ -132,6 +134,16 @@ expressions:
           * (Generator_previous_status - Generator_status)
     otherwise: Generator_ramp_down_rate * Generator_p_nom_effective
 
+masks:
+  Generator_ramps_from_previous:
+    description: >-
+      a snapshot whose ramp reads a previous output — any snapshot but its
+      period's first, and the horizon's first where the generator comes in off
+      or carries an initial output
+    where: >-
+      position(snapshot, within=snapshot_period[period]) > 0 OR (position(snapshot) == 0 AND
+      (Generator_status_initial == 0 OR Generator_p_init))
+
 constraints:
   Generator_p_ramp_limit_up_run_big_m:
     description: >-
@@ -140,10 +152,9 @@ constraints:
       releases the row in the snapshot it turns on
     dims: [scenario, snapshot, generator]
     where: >-
-      Generator_committable AND Generator_p_nom_extendable AND NOT (Generator_p_nom_mod > 0)
+      Generator_com_ext
       AND (Generator_ramp_limit_up OR Generator_ramp_limit_start_up)
-      AND (position(snapshot, within=snapshot_period[period]) > 0 OR (position(snapshot) == 0 AND (Generator_status_initial == 0 OR Generator_p_init)))
-      AND Generator_active
+      AND Generator_ramps_from_previous
     expression: >-
       Generator_p - Generator_previous_p <=
       Generator_ramp_up_rate * Generator_p_nom_ext
@@ -155,10 +166,9 @@ constraints:
       the chosen build; the big M releases the row everywhere else
     dims: [scenario, snapshot, generator]
     where: >-
-      Generator_committable AND Generator_p_nom_extendable AND NOT (Generator_p_nom_mod > 0)
+      Generator_com_ext
       AND (Generator_ramp_limit_up OR Generator_ramp_limit_start_up)
-      AND (position(snapshot, within=snapshot_period[period]) > 0 OR (position(snapshot) == 0 AND (Generator_status_initial == 0 OR Generator_p_init)))
-      AND Generator_active
+      AND Generator_ramps_from_previous
     expression: >-
       Generator_p - Generator_previous_p <=
       Generator_start_up_rate * Generator_p_nom_ext
@@ -170,10 +180,9 @@ constraints:
       releases the row in the snapshot it turns off
     dims: [scenario, snapshot, generator]
     where: >-
-      Generator_committable AND Generator_p_nom_extendable AND NOT (Generator_p_nom_mod > 0)
+      Generator_com_ext
       AND (Generator_ramp_limit_down OR Generator_ramp_limit_shut_down)
-      AND (position(snapshot, within=snapshot_period[period]) > 0 OR (position(snapshot) == 0 AND (Generator_status_initial == 0 OR Generator_p_init)))
-      AND Generator_active
+      AND Generator_ramps_from_previous
     expression: >-
       Generator_previous_p - Generator_p <=
       Generator_ramp_down_rate * Generator_p_nom_ext
@@ -185,10 +194,9 @@ constraints:
       the chosen build; the big M releases the row everywhere else
     dims: [scenario, snapshot, generator]
     where: >-
-      Generator_committable AND Generator_p_nom_extendable AND NOT (Generator_p_nom_mod > 0)
+      Generator_com_ext
       AND (Generator_ramp_limit_down OR Generator_ramp_limit_shut_down)
-      AND (position(snapshot, within=snapshot_period[period]) > 0 OR (position(snapshot) == 0 AND (Generator_status_initial == 0 OR Generator_p_init)))
-      AND Generator_active
+      AND Generator_ramps_from_previous
     expression: >-
       Generator_previous_p - Generator_p <=
       Generator_shut_down_rate * Generator_p_nom_ext
@@ -205,7 +213,7 @@ constraints:
     where: >-
       (Generator_ramp_limit_up OR Generator_ramp_limit_start_up)
       AND NOT (Generator_committable AND Generator_p_nom_extendable AND NOT (Generator_p_nom_mod > 0))
-      AND (position(snapshot, within=snapshot_period[period]) > 0 OR (position(snapshot) == 0 AND (Generator_status_initial == 0 OR Generator_p_init)))
+      AND Generator_ramps_from_previous
       AND Generator_active
     expression: Generator_p - Generator_previous_p <= Generator_ramp_up_allowance
   Generator_p_ramp_limit_down:
@@ -220,7 +228,7 @@ constraints:
     where: >-
       (Generator_ramp_limit_down OR Generator_ramp_limit_shut_down)
       AND NOT (Generator_committable AND Generator_p_nom_extendable AND NOT (Generator_p_nom_mod > 0))
-      AND (position(snapshot, within=snapshot_period[period]) > 0 OR (position(snapshot) == 0 AND (Generator_status_initial == 0 OR Generator_p_init)))
+      AND Generator_ramps_from_previous
       AND Generator_active
     expression: Generator_previous_p - Generator_p <= Generator_ramp_down_allowance
 
diff --git a/examples/pypsa/line.yaml b/examples/pypsa/line.yaml
index 2eb5750a..66c5138a 100644
--- a/examples/pypsa/line.yaml
+++ b/examples/pypsa/line.yaml
@@ -168,7 +168,7 @@ variables:
       cost and held up by the cuts; absent, and zero in the balance, where
       the network is lossless
     dims: [scenario, snapshot, line]
-    where: transmission_losses AND Line_active
+    where: Line_lossy
     absence: zero
     bounds:
       lower: 0
@@ -236,6 +236,13 @@ expressions:
     expression: sum(Line_s * at(Line_cycle_weight, by=snapshot_period[period]), over=line)
     adds_to: Cycle_angle_sum
 
+masks:
+  Line_lossy:
+    description: >-
+      a line that stands in the snapshot's period, where the run models
+      transmission losses
+    where: transmission_losses AND Line_active
+
 constraints:
   Line_fix_s_lower:
     description: "`Line-fix-s-lower` — a fixed line carries at least the negative of its rating, the loss counted against it"
@@ -300,7 +307,7 @@ constraints:
   Line_loss_upper:
     description: "`Line-loss_upper` — a line dissipates at most the loss at its rating"
     dims: [scenario, snapshot, line]
-    where: transmission_losses AND Line_active
+    where: Line_lossy
     expression: Line_loss <= Line_loss_max
   Line_loss_tangents_forward:
     description: >-
@@ -309,12 +316,12 @@ constraints:
       `k`, or one row stacked over its `secant` axis, and this block states them
       all over the segment dimension
     dims: [scenario, snapshot, line, segment]
-    where: transmission_losses AND Line_active
+    where: Line_lossy
     expression: Line_loss + Line_loss_slope * Line_s >= Line_loss_offset
   Line_loss_tangents_reverse:
     description: >-
       `Line-loss_tangents-{k}--1`, `Line-loss_secants-neg` — the same fan
       mirrored, the loss depending on the flow's magnitude
     dims: [scenario, snapshot, line, segment]
-    where: transmission_losses AND Line_active
+    where: Line_lossy
     expression: Line_loss - Line_loss_slope * Line_s >= Line_loss_offset
diff --git a/examples/pypsa/link.yaml b/examples/pypsa/link.yaml
index 08fe4389..54d6665d 100644
--- a/examples/pypsa/link.yaml
+++ b/examples/pypsa/link.yaml
@@ -267,6 +267,13 @@ expressions:
       + sum(Link_output_arrival, over=link_output, by=Link_output_bus[bus])
     adds_to: Bus_injection
 
+masks:
+  Link_committed:
+    description: >-
+      a committable link that stands in the snapshot's period — every
+      unit-commitment row's set
+    where: Link_committable AND Link_active
+
 constraints:
   Link_fix_p_lower:
     description: "`Link-fix-p-lower` — a fixed link carries at least its minimum, negative for the other way"
diff --git a/examples/pypsa/link_commitment.yaml b/examples/pypsa/link_commitment.yaml
index 51f9c736..3583a238 100644
--- a/examples/pypsa/link_commitment.yaml
+++ b/examples/pypsa/link_commitment.yaml
@@ -81,21 +81,21 @@ variables:
       the rows below cap at one, or at the module count where the build is
       modular
     dims: [scenario, snapshot, link]
-    where: Link_committable AND Link_active
+    where: Link_committed
     domain: integer
     bounds:
       lower: 0
   Link_start_up:
     description: "`Link-start_up` — how much of a committable link turns on this snapshot, capped as the status is"
     dims: [scenario, snapshot, link]
-    where: Link_committable AND Link_active
+    where: Link_committed
     domain: integer
     bounds:
       lower: 0
   Link_shut_down:
     description: "`Link-shut_down` — how much of a committable link turns off this snapshot, capped as the status is"
     dims: [scenario, snapshot, link]
-    where: Link_committable AND Link_active
+    where: Link_committed
     domain: integer
     bounds:
       lower: 0
@@ -121,6 +121,8 @@ given:
     Link_p_nom_ext: { dims: [link] }
   expressions:
     scenario_opex: { dims: [scenario] }
+  masks:
+    Link_committed: { dims: [snapshot, link] }
 
 expressions:
   Link_previous_status:
@@ -148,26 +150,38 @@ expressions:
       + sum(sum(Link_shut_down * Link_shut_down_cost, over=link), over=snapshot)
     adds_to: scenario_opex
 
+masks:
+  Link_com_ext:
+    description: >-
+      a committable link with an extendable, non-modular build that stands in
+      the snapshot's period — PyPSA's `com-ext` rows, whose status is relaxed
+      against the chosen build
+    where: >-
+      Link_committable
+      AND Link_p_nom_extendable
+      AND NOT (Link_p_nom_mod > 0)
+      AND Link_active
+
 constraints:
   Link_com_p_lower:
     description: "`Link-com-p-lower` — a committed link flows at least its minimum; off, at least nothing"
     dims: [scenario, snapshot, link]
-    where: Link_committable AND not Link_p_nom_extendable AND NOT (Link_p_nom_mod > 0) AND Link_active
+    where: Link_committed AND NOT Link_p_nom_extendable AND NOT (Link_p_nom_mod > 0)
     expression: Link_p >= Link_p_min_pu * Link_p_nom * (Link_status - Link_maintenance_pu * Link_maintenance_status)
   Link_com_p_upper:
     description: "`Link-com-p-upper` — a committed link flows at most what is available; off, at most nothing"
     dims: [scenario, snapshot, link]
-    where: Link_committable AND not Link_p_nom_extendable AND NOT (Link_p_nom_mod > 0) AND Link_active
+    where: Link_committed AND NOT Link_p_nom_extendable AND NOT (Link_p_nom_mod > 0)
     expression: Link_p <= Link_p_max_pu * Link_p_nom * (Link_status - Link_maintenance_pu * Link_maintenance_status)
   Link_com_transition_start_up:
     description: "`Link-com-transition-start-up` — turning on is a start, counted against the state the link carried into the snapshot"
     dims: [scenario, snapshot, link]
-    where: Link_committable AND Link_active
+    where: Link_committed
     expression: Link_start_up >= Link_status - Link_previous_status
   Link_com_transition_shut_down:
     description: "`Link-com-transition-shut-down` — turning off is a stop, counted against the state the link carried into the snapshot"
     dims: [scenario, snapshot, link]
-    where: Link_committable AND Link_active
+    where: Link_committed
     expression: Link_shut_down >= Link_previous_status - Link_status
   Link_com_up_time:
     description: >-
@@ -175,7 +189,7 @@ constraints:
       is still on. The first snapshot's share of the window is the brought-in
       up time's, which the must-stay-up mask carries
     dims: [scenario, snapshot, link]
-    where: Link_committable AND Link_min_up_time > 0 AND position(snapshot) > 0 AND Link_active
+    where: Link_committed AND Link_min_up_time > 0 AND position(snapshot) > 0
     expression: sum_back(Link_start_up, along=snapshot, window=Link_min_up_time) <= Link_status
   Link_com_down_time:
     description: >-
@@ -183,38 +197,38 @@ constraints:
       time is still off. The first snapshot's share of the window is the
       brought-in down time's, which the must-stay-down mask carries
     dims: [scenario, snapshot, link]
-    where: Link_committable AND Link_min_down_time > 0 AND position(snapshot) > 0 AND Link_active
+    where: Link_committed AND Link_min_down_time > 0 AND position(snapshot) > 0
     expression: sum_back(Link_shut_down, along=snapshot, window=Link_min_down_time) <= 1 - Link_status
   Link_com_status_must_stay_up:
     description: "`Link-com-status-min_up_time_must_stay_up` — a link still serving the up time it brought in stays on"
     dims: [scenario, snapshot, link]
-    where: Link_committable AND Link_must_stay_up AND Link_active
+    where: Link_committed AND Link_must_stay_up
     expression: Link_status == 1
   Link_com_status_must_stay_down:
     description: >-
       `Link-com-status-min_down_time_must_stay_up` — a link still serving
       the down time it brought in stays off; PyPSA names the row `_must_stay_up`
     dims: [scenario, snapshot, link]
-    where: Link_committable AND Link_must_stay_down AND Link_active
+    where: Link_committed AND Link_must_stay_down
     expression: Link_status == 0
   Link_com_ext_p_upper_cap:
     description: >-
       `Link-com-ext-p-upper-cap` — a committed extendable link flows
       at most what is available of the chosen build, whatever its status
     dims: [scenario, snapshot, link]
-    where: Link_committable AND Link_p_nom_extendable AND NOT (Link_p_nom_mod > 0) AND Link_active
+    where: Link_com_ext
     expression: Link_p <= Link_p_max_pu * (Link_p_nom_ext - Link_maintenance_pu * Link_maintenance_capacity)
   Link_com_ext_p_upper_big_m:
     description: "`Link-com-ext-p-upper-bigM` — off, a link flows nothing; on, the big M is no bound"
     dims: [scenario, snapshot, link]
-    where: Link_committable AND Link_p_nom_extendable AND NOT (Link_p_nom_mod > 0) AND Link_active
+    where: Link_com_ext
     expression: Link_p <= Link_big_m * Link_status
   Link_com_ext_p_lower:
     description: >-
       `Link-com-ext-p-lower` — a committed extendable link flows at
       least its minimum of the chosen build; off, the big M releases the row
     dims: [scenario, snapshot, link]
-    where: Link_committable AND Link_p_nom_extendable AND NOT (Link_p_nom_mod > 0) AND Link_active
+    where: Link_com_ext
     expression: >-
       Link_p >=
       Link_p_min_pu * (Link_p_nom_ext - Link_maintenance_pu * Link_maintenance_capacity)
@@ -225,23 +239,21 @@ constraints:
       negative, flow is also plainly non-negative, a row the big-M lower
       cannot assert while the link is off
     dims: [scenario, snapshot, link]
-    where: >-
-      Link_committable AND Link_p_nom_extendable
-      AND Link_p_min_pu_nonneg AND NOT (Link_p_nom_mod > 0) AND Link_active
+    where: Link_com_ext AND Link_p_min_pu_nonneg
     expression: Link_p >= 0
   Link_com_mod_p_lower:
     description: >-
       `Link-com-mod-p-lower` — a committed modular link flows at least
       its minimum of one module, whether the build is fixed or a decision
     dims: [scenario, snapshot, link]
-    where: Link_committable AND Link_p_nom_mod > 0 AND Link_active
+    where: Link_committed AND Link_p_nom_mod > 0
     expression: Link_p >= Link_p_min_pu * Link_p_nom_mod * (Link_status - Link_maintenance_pu * Link_maintenance_status)
   Link_com_mod_p_upper:
     description: >-
       `Link-com-mod-p-upper` — a committed modular link flows at most
       one module's share, whether the build is fixed or a decision
     dims: [scenario, snapshot, link]
-    where: Link_committable AND Link_p_nom_mod > 0 AND Link_active
+    where: Link_committed AND Link_p_nom_mod > 0
     expression: Link_p <= Link_p_max_pu * Link_p_nom_mod * (Link_status - Link_maintenance_pu * Link_maintenance_status)
   Link_status_p_fixed_upper:
     description: >-
@@ -249,7 +261,7 @@ constraints:
       place, an explicit row as PyPSA writes it: one where the build is not
       modular, and the fixed build's whole count of modules where it is
     dims: [scenario, snapshot, link]
-    where: Link_committable AND NOT (Link_p_nom_extendable AND Link_p_nom_mod > 0) AND Link_active
+    where: Link_committed AND NOT (Link_p_nom_extendable AND Link_p_nom_mod > 0)
     expression: Link_status <= Link_modules_installed
   Link_start_up_p_fixed_upper:
     description: >-
@@ -257,7 +269,7 @@ constraints:
       place, an explicit row as PyPSA writes it: one where the build is not
       modular, and the fixed build's whole count of modules where it is
     dims: [scenario, snapshot, link]
-    where: Link_committable AND NOT (Link_p_nom_extendable AND Link_p_nom_mod > 0) AND Link_active
+    where: Link_committed AND NOT (Link_p_nom_extendable AND Link_p_nom_mod > 0)
     expression: Link_start_up <= Link_modules_installed
   Link_shut_down_p_fixed_upper:
     description: >-
@@ -265,20 +277,20 @@ constraints:
       place, an explicit row as PyPSA writes it: one where the build is not
       modular, and the fixed build's whole count of modules where it is
     dims: [scenario, snapshot, link]
-    where: Link_committable AND NOT (Link_p_nom_extendable AND Link_p_nom_mod > 0) AND Link_active
+    where: Link_committed AND NOT (Link_p_nom_extendable AND Link_p_nom_mod > 0)
     expression: Link_shut_down <= Link_modules_installed
   Link_status_p_nom_variable_upper:
     description: "`Link-status-p_nom-variable-upper` — a modular link is on only where a module is built"
     dims: [scenario, snapshot, link]
-    where: Link_committable AND Link_p_nom_extendable AND Link_p_nom_mod > 0 AND Link_active
+    where: Link_committed AND Link_p_nom_extendable AND Link_p_nom_mod > 0
     expression: Link_status <= Link_n_mod
   Link_start_up_p_nom_variable_upper:
     description: "`Link-start_up-p_nom-variable-upper` — a modular link starts only where a module is built"
     dims: [scenario, snapshot, link]
-    where: Link_committable AND Link_p_nom_extendable AND Link_p_nom_mod > 0 AND Link_active
+    where: Link_committed AND Link_p_nom_extendable AND Link_p_nom_mod > 0
     expression: Link_start_up <= Link_n_mod
   Link_shut_down_p_nom_variable_upper:
     description: "`Link-shut_down-p_nom-variable-upper` — a modular link stops only where a module is built"
     dims: [scenario, snapshot, link]
-    where: Link_committable AND Link_p_nom_extendable AND Link_p_nom_mod > 0 AND Link_active
+    where: Link_committed AND Link_p_nom_extendable AND Link_p_nom_mod > 0
     expression: Link_shut_down <= Link_n_mod
diff --git a/examples/pypsa/link_maintenance.yaml b/examples/pypsa/link_maintenance.yaml
index aefd65cd..4388395b 100644
--- a/examples/pypsa/link_maintenance.yaml
+++ b/examples/pypsa/link_maintenance.yaml
@@ -75,9 +75,7 @@ variables:
       `Link-maintenance_capacity` — the chosen build while in maintenance, zero
       otherwise: the product the `maintcap` rows linearize
     dims: [scenario, snapshot, link]
-    where: >-
-      Link_maintainable AND Link_p_nom_extendable
-      AND NOT (Link_committable AND Link_p_nom_mod > 0) AND Link_active
+    where: Link_maint_ext
     absence: zero
     bounds:
       lower: 0
@@ -87,9 +85,7 @@ variables:
       otherwise: the product the `maint-status` rows linearize, so a unit in
       maintenance may also be off
     dims: [scenario, snapshot, link]
-    where: >-
-      Link_maintainable AND Link_committable
-      AND NOT (Link_p_nom_extendable AND NOT (Link_p_nom_mod > 0)) AND Link_active
+    where: Link_maintainable AND Link_committed AND NOT (Link_p_nom_extendable AND NOT (Link_p_nom_mod > 0))
     absence: zero
     bounds:
       lower: 0
@@ -106,6 +102,20 @@ given:
   variables:
     Link_status: { dims: [scenario, snapshot, link], domain: integer }
     Link_p_nom_ext: { dims: [link] }
+  masks:
+    Link_committed: { dims: [snapshot, link] }
+
+masks:
+  Link_maint_ext:
+    description: >-
+      a maintainable link with an extendable build, unless it is committable
+      and modular, that stands in the snapshot's period — the maintenance rows
+      against the chosen build
+    where: >-
+      Link_maintainable
+      AND Link_p_nom_extendable
+      AND NOT (Link_committable AND Link_p_nom_mod > 0)
+      AND Link_active
 
 constraints:
   Link_maint_event_count:
@@ -131,54 +141,54 @@ constraints:
       `Link-maintcap_upper` — the build taken off is at most the chosen build in
       maintenance, and at most the build less its floor out of it
     dims: [scenario, snapshot, link]
-    where: Link_maintainable AND Link_p_nom_extendable AND NOT (Link_committable AND Link_p_nom_mod > 0) AND Link_active
+    where: Link_maint_ext
     expression: Link_maintenance_capacity <= Link_p_nom_ext - Link_p_nom_min * (1 - Link_maintenance)
   Link_maintcap_upper_nommax:
     description: "`Link-maintcap_upper_nommax` — out of maintenance, no build is taken off"
     dims: [scenario, snapshot, link]
-    where: Link_maintainable AND Link_p_nom_extendable AND NOT (Link_committable AND Link_p_nom_mod > 0) AND Link_active
+    where: Link_maint_ext
     expression: Link_maintenance_capacity <= Link_p_nom_max * Link_maintenance
   Link_maintcap_lower_nommax:
     description: "`Link-maintcap_lower_nommax` — in maintenance, the whole chosen build is taken off"
     dims: [scenario, snapshot, link]
-    where: Link_maintainable AND Link_p_nom_extendable AND NOT (Link_committable AND Link_p_nom_mod > 0) AND Link_active
+    where: Link_maint_ext
     expression: Link_maintenance_capacity >= Link_p_nom_ext - Link_p_nom_max * (1 - Link_maintenance)
   Link_maintcap_lower_nommin:
     description: "`Link-maintcap_lower_nommin` — in maintenance, at least the floor of the build is taken off"
     dims: [scenario, snapshot, link]
-    where: Link_maintainable AND Link_p_nom_extendable AND NOT (Link_committable AND Link_p_nom_mod > 0) AND Link_active AND Link_p_nom_min > 0
+    where: Link_maint_ext AND Link_p_nom_min > 0
     expression: Link_maintenance_capacity >= Link_p_nom_min * Link_maintenance
   Link_maint_status_le_status:
     description: "`Link-maint-status-le-status` — the status in maintenance is at most the status"
     dims: [scenario, snapshot, link]
-    where: Link_maintainable AND Link_committable AND NOT Link_p_nom_extendable AND NOT (Link_p_nom_mod > 0) AND Link_active
+    where: Link_maintainable AND Link_committed AND NOT Link_p_nom_extendable AND NOT (Link_p_nom_mod > 0)
     expression: Link_maintenance_status <= Link_status
   Link_maint_status_le_maint:
     description: "`Link-maint-status-le-maint` — out of maintenance, the status in maintenance is zero"
     dims: [scenario, snapshot, link]
-    where: Link_maintainable AND Link_committable AND NOT Link_p_nom_extendable AND NOT (Link_p_nom_mod > 0) AND Link_active
+    where: Link_maintainable AND Link_committed AND NOT Link_p_nom_extendable AND NOT (Link_p_nom_mod > 0)
     expression: Link_maintenance_status <= Link_maintenance
   Link_maint_status_lb:
     description: "`Link-maint-status-lb` — on and in maintenance, the status in maintenance is one"
     dims: [scenario, snapshot, link]
-    where: Link_maintainable AND Link_committable AND NOT Link_p_nom_extendable AND NOT (Link_p_nom_mod > 0) AND Link_active
+    where: Link_maintainable AND Link_committed AND NOT Link_p_nom_extendable AND NOT (Link_p_nom_mod > 0)
     expression: Link_maintenance_status >= Link_status + Link_maintenance - 1
   Link_maint_modstatus_le_status:
     description: "`Link-maint-modstatus-le-status` — the modules on in maintenance are at most the modules on"
     dims: [scenario, snapshot, link]
-    where: Link_maintainable AND Link_committable AND Link_p_nom_mod > 0 AND Link_active
+    where: Link_maintainable AND Link_committed AND Link_p_nom_mod > 0
     expression: Link_maintenance_status <= Link_status
   Link_maint_modstatus_le_maint:
     description: >-
       `Link-maint-modstatus-le-maint` — out of maintenance, no module is on in
       maintenance; in it, at most the modules the build cap holds
     dims: [scenario, snapshot, link]
-    where: Link_maintainable AND Link_committable AND Link_p_nom_mod > 0 AND Link_active
+    where: Link_maintainable AND Link_committed AND Link_p_nom_mod > 0
     expression: Link_maintenance_status <= Link_p_nom_max / Link_p_nom_mod * Link_maintenance
   Link_maint_modstatus_lb:
     description: "`Link-maint-modstatus-lb` — in maintenance, every module on is on in maintenance"
     dims: [scenario, snapshot, link]
-    where: Link_maintainable AND Link_committable AND Link_p_nom_mod > 0 AND Link_active
+    where: Link_maintainable AND Link_committed AND Link_p_nom_mod > 0
     expression: Link_maintenance_status >= Link_status - Link_p_nom_max / Link_p_nom_mod * (1 - Link_maintenance)
 
 assumptions:
diff --git a/examples/pypsa/link_ramping.yaml b/examples/pypsa/link_ramping.yaml
index 4dd25f7c..66db2331 100644
--- a/examples/pypsa/link_ramping.yaml
+++ b/examples/pypsa/link_ramping.yaml
@@ -60,6 +60,8 @@ given:
     Link_p_nom_effective: { dims: [scenario, link] }
     Link_previous_status: { dims: [scenario, snapshot, link] }
     Link_p_nom_committed: { dims: [scenario, link] }
+  masks:
+    Link_com_ext: { dims: [snapshot, link] }
 
 expressions:
   Link_previous_p:
@@ -132,6 +134,16 @@ expressions:
           * (Link_previous_status - Link_status)
     otherwise: Link_ramp_down_rate * Link_p_nom_effective
 
+masks:
+  Link_ramps_from_previous:
+    description: >-
+      a snapshot whose ramp reads a previous output — any snapshot but its
+      period's first, and the horizon's first where the link comes in off or
+      carries an initial output
+    where: >-
+      position(snapshot, within=snapshot_period[period]) > 0 OR (position(snapshot) == 0 AND
+      (Link_status_initial == 0 OR Link_p_init))
+
 constraints:
   Link_p_ramp_limit_up_run_big_m:
     description: >-
@@ -139,11 +151,7 @@ constraints:
       raises flow no faster than its limit of the chosen build; the big M
       releases the row in the snapshot it turns on
     dims: [scenario, snapshot, link]
-    where: >-
-      Link_committable AND Link_p_nom_extendable AND NOT (Link_p_nom_mod > 0)
-      AND (Link_ramp_limit_up OR Link_ramp_limit_start_up)
-      AND (position(snapshot, within=snapshot_period[period]) > 0 OR (position(snapshot) == 0 AND (Link_status_initial == 0 OR Link_p_init)))
-      AND Link_active
+    where: Link_com_ext AND (Link_ramp_limit_up OR Link_ramp_limit_start_up) AND Link_ramps_from_previous
     expression: >-
       Link_p - Link_previous_p <=
       Link_ramp_up_rate * Link_p_nom_ext
@@ -154,11 +162,7 @@ constraints:
       committed extendable link ramps no further than its start-up ramp of
       the chosen build; the big M releases the row everywhere else
     dims: [scenario, snapshot, link]
-    where: >-
-      Link_committable AND Link_p_nom_extendable AND NOT (Link_p_nom_mod > 0)
-      AND (Link_ramp_limit_up OR Link_ramp_limit_start_up)
-      AND (position(snapshot, within=snapshot_period[period]) > 0 OR (position(snapshot) == 0 AND (Link_status_initial == 0 OR Link_p_init)))
-      AND Link_active
+    where: Link_com_ext AND (Link_ramp_limit_up OR Link_ramp_limit_start_up) AND Link_ramps_from_previous
     expression: >-
       Link_p - Link_previous_p <=
       Link_start_up_rate * Link_p_nom_ext
@@ -169,11 +173,7 @@ constraints:
       lowers flow no faster than its limit of the chosen build; the big M
       releases the row in the snapshot it turns off
     dims: [scenario, snapshot, link]
-    where: >-
-      Link_committable AND Link_p_nom_extendable AND NOT (Link_p_nom_mod > 0)
-      AND (Link_ramp_limit_down OR Link_ramp_limit_shut_down)
-      AND (position(snapshot, within=snapshot_period[period]) > 0 OR (position(snapshot) == 0 AND (Link_status_initial == 0 OR Link_p_init)))
-      AND Link_active
+    where: Link_com_ext AND (Link_ramp_limit_down OR Link_ramp_limit_shut_down) AND Link_ramps_from_previous
     expression: >-
       Link_previous_p - Link_p <=
       Link_ramp_down_rate * Link_p_nom_ext
@@ -184,11 +184,7 @@ constraints:
       a committed extendable link ramps no further than its shut-down ramp of
       the chosen build; the big M releases the row everywhere else
     dims: [scenario, snapshot, link]
-    where: >-
-      Link_committable AND Link_p_nom_extendable AND NOT (Link_p_nom_mod > 0)
-      AND (Link_ramp_limit_down OR Link_ramp_limit_shut_down)
-      AND (position(snapshot, within=snapshot_period[period]) > 0 OR (position(snapshot) == 0 AND (Link_status_initial == 0 OR Link_p_init)))
-      AND Link_active
+    where: Link_com_ext AND (Link_ramp_limit_down OR Link_ramp_limit_shut_down) AND Link_ramps_from_previous
     expression: >-
       Link_previous_p - Link_p <=
       Link_shut_down_rate * Link_p_nom_ext
@@ -205,7 +201,7 @@ constraints:
     where: >-
       (Link_ramp_limit_up OR Link_ramp_limit_start_up)
       AND NOT (Link_committable AND Link_p_nom_extendable AND NOT (Link_p_nom_mod > 0))
-      AND (position(snapshot, within=snapshot_period[period]) > 0 OR (position(snapshot) == 0 AND (Link_status_initial == 0 OR Link_p_init)))
+      AND Link_ramps_from_previous
       AND Link_active
     expression: Link_p - Link_previous_p <= Link_ramp_up_allowance
   Link_p_ramp_limit_down:
@@ -220,7 +216,7 @@ constraints:
     where: >-
       (Link_ramp_limit_down OR Link_ramp_limit_shut_down)
       AND NOT (Link_committable AND Link_p_nom_extendable AND NOT (Link_p_nom_mod > 0))
-      AND (position(snapshot, within=snapshot_period[period]) > 0 OR (position(snapshot) == 0 AND (Link_status_initial == 0 OR Link_p_init)))
+      AND Link_ramps_from_previous
       AND Link_active
     expression: Link_previous_p - Link_p <= Link_ramp_down_allowance
 
diff --git a/examples/pypsa/process.yaml b/examples/pypsa/process.yaml
index fa9ee966..6271553e 100644
--- a/examples/pypsa/process.yaml
+++ b/examples/pypsa/process.yaml
@@ -238,6 +238,13 @@ expressions:
       sum(Process_output_arrival, over=process_output, by=Process_output_bus[bus])
     adds_to: Bus_injection
 
+masks:
+  Process_committed:
+    description: >-
+      a committable process that stands in the snapshot's period — every
+      unit-commitment row's set
+    where: Process_committable AND Process_active
+
 constraints:
   Process_fix_p_lower:
     description: "`Process-fix-p-lower` — a fixed process runs at least its minimum, negative for the other way"
diff --git a/examples/pypsa/process_commitment.yaml b/examples/pypsa/process_commitment.yaml
index 134c82a9..c1751f27 100644
--- a/examples/pypsa/process_commitment.yaml
+++ b/examples/pypsa/process_commitment.yaml
@@ -81,21 +81,21 @@ variables:
       the rows below cap at one, or at the module count where the build is
       modular
     dims: [scenario, snapshot, process]
-    where: Process_committable AND Process_active
+    where: Process_committed
     domain: integer
     bounds:
       lower: 0
   Process_start_up:
     description: "`Process-start_up` — how much of a committable process turns on this snapshot, capped as the status is"
     dims: [scenario, snapshot, process]
-    where: Process_committable AND Process_active
+    where: Process_committed
     domain: integer
     bounds:
       lower: 0
   Process_shut_down:
     description: "`Process-shut_down` — how much of a committable process turns off this snapshot, capped as the status is"
     dims: [scenario, snapshot, process]
-    where: Process_committable AND Process_active
+    where: Process_committed
     domain: integer
     bounds:
       lower: 0
@@ -121,6 +121,8 @@ given:
     Process_p_nom_ext: { dims: [process] }
   expressions:
     scenario_opex: { dims: [scenario] }
+  masks:
+    Process_committed: { dims: [snapshot, process] }
 
 expressions:
   Process_previous_status:
@@ -148,26 +150,38 @@ expressions:
       + sum(sum(Process_shut_down * Process_shut_down_cost, over=process), over=snapshot)
     adds_to: scenario_opex
 
+masks:
+  Process_com_ext:
+    description: >-
+      a committable process with an extendable, non-modular build that stands
+      in the snapshot's period — PyPSA's `com-ext` rows, whose status is
+      relaxed against the chosen build
+    where: >-
+      Process_committable
+      AND Process_p_nom_extendable
+      AND NOT (Process_p_nom_mod > 0)
+      AND Process_active
+
 constraints:
   Process_com_p_lower:
     description: "`Process-com-p-lower` — a committed process runs at least its minimum; off, at least nothing"
     dims: [scenario, snapshot, process]
-    where: Process_committable AND not Process_p_nom_extendable AND NOT (Process_p_nom_mod > 0) AND Process_active
+    where: Process_committed AND NOT Process_p_nom_extendable AND NOT (Process_p_nom_mod > 0)
     expression: Process_p >= Process_p_min_pu * Process_p_nom * (Process_status - Process_maintenance_pu * Process_maintenance_status)
   Process_com_p_upper:
     description: "`Process-com-p-upper` — a committed process runs at most what is available; off, at most nothing"
     dims: [scenario, snapshot, process]
-    where: Process_committable AND not Process_p_nom_extendable AND NOT (Process_p_nom_mod > 0) AND Process_active
+    where: Process_committed AND NOT Process_p_nom_extendable AND NOT (Process_p_nom_mod > 0)
     expression: Process_p <= Process_p_max_pu * Process_p_nom * (Process_status - Process_maintenance_pu * Process_maintenance_status)
   Process_com_transition_start_up:
     description: "`Process-com-transition-start-up` — turning on is a start, counted against the state the process carried into the snapshot"
     dims: [scenario, snapshot, process]
-    where: Process_committable AND Process_active
+    where: Process_committed
     expression: Process_start_up >= Process_status - Process_previous_status
   Process_com_transition_shut_down:
     description: "`Process-com-transition-shut-down` — turning off is a stop, counted against the state the process carried into the snapshot"
     dims: [scenario, snapshot, process]
-    where: Process_committable AND Process_active
+    where: Process_committed
     expression: Process_shut_down >= Process_previous_status - Process_status
   Process_com_up_time:
     description: >-
@@ -175,7 +189,7 @@ constraints:
       is still on. The first snapshot's share of the window is the brought-in
       up time's, which the must-stay-up mask carries
     dims: [scenario, snapshot, process]
-    where: Process_committable AND Process_min_up_time > 0 AND position(snapshot) > 0 AND Process_active
+    where: Process_committed AND Process_min_up_time > 0 AND position(snapshot) > 0
     expression: sum_back(Process_start_up, along=snapshot, window=Process_min_up_time) <= Process_status
   Process_com_down_time:
     description: >-
@@ -183,38 +197,38 @@ constraints:
       time is still off. The first snapshot's share of the window is the
       brought-in down time's, which the must-stay-down mask carries
     dims: [scenario, snapshot, process]
-    where: Process_committable AND Process_min_down_time > 0 AND position(snapshot) > 0 AND Process_active
+    where: Process_committed AND Process_min_down_time > 0 AND position(snapshot) > 0
     expression: sum_back(Process_shut_down, along=snapshot, window=Process_min_down_time) <= 1 - Process_status
   Process_com_status_must_stay_up:
     description: "`Process-com-status-min_up_time_must_stay_up` — a process still serving the up time it brought in stays on"
     dims: [scenario, snapshot, process]
-    where: Process_committable AND Process_must_stay_up AND Process_active
+    where: Process_committed AND Process_must_stay_up
     expression: Process_status == 1
   Process_com_status_must_stay_down:
     description: >-
       `Process-com-status-min_down_time_must_stay_up` — a process still serving
       the down time it brought in stays off; PyPSA names the row `_must_stay_up`
     dims: [scenario, snapshot, process]
-    where: Process_committable AND Process_must_stay_down AND Process_active
+    where: Process_committed AND Process_must_stay_down
     expression: Process_status == 0
   Process_com_ext_p_upper_cap:
     description: >-
       `Process-com-ext-p-upper-cap` — a committed extendable process runs
       at most what is available of the chosen build, whatever its status
     dims: [scenario, snapshot, process]
-    where: Process_committable AND Process_p_nom_extendable AND NOT (Process_p_nom_mod > 0) AND Process_active
+    where: Process_com_ext
     expression: Process_p <= Process_p_max_pu * (Process_p_nom_ext - Process_maintenance_pu * Process_maintenance_capacity)
   Process_com_ext_p_upper_big_m:
     description: "`Process-com-ext-p-upper-bigM` — off, a process does not run; on, the big M is no bound"
     dims: [scenario, snapshot, process]
-    where: Process_committable AND Process_p_nom_extendable AND NOT (Process_p_nom_mod > 0) AND Process_active
+    where: Process_com_ext
     expression: Process_p <= Process_big_m * Process_status
   Process_com_ext_p_lower:
     description: >-
       `Process-com-ext-p-lower` — a committed extendable process runs at
       least its minimum of the chosen build; off, the big M releases the row
     dims: [scenario, snapshot, process]
-    where: Process_committable AND Process_p_nom_extendable AND NOT (Process_p_nom_mod > 0) AND Process_active
+    where: Process_com_ext
     expression: >-
       Process_p >=
       Process_p_min_pu * (Process_p_nom_ext - Process_maintenance_pu * Process_maintenance_capacity)
@@ -225,23 +239,21 @@ constraints:
       negative, internal power is also plainly non-negative, a row the big-M lower
       cannot assert while the process is off
     dims: [scenario, snapshot, process]
-    where: >-
-      Process_committable AND Process_p_nom_extendable
-      AND Process_p_min_pu_nonneg AND NOT (Process_p_nom_mod > 0) AND Process_active
+    where: Process_com_ext AND Process_p_min_pu_nonneg
     expression: Process_p >= 0
   Process_com_mod_p_lower:
     description: >-
       `Process-com-mod-p-lower` — a committed modular process runs at least
       its minimum of one module, whether the build is fixed or a decision
     dims: [scenario, snapshot, process]
-    where: Process_committable AND Process_p_nom_mod > 0 AND Process_active
+    where: Process_committed AND Process_p_nom_mod > 0
     expression: Process_p >= Process_p_min_pu * Process_p_nom_mod * (Process_status - Process_maintenance_pu * Process_maintenance_status)
   Process_com_mod_p_upper:
     description: >-
       `Process-com-mod-p-upper` — a committed modular process runs at most
       one module's share, whether the build is fixed or a decision
     dims: [scenario, snapshot, process]
-    where: Process_committable AND Process_p_nom_mod > 0 AND Process_active
+    where: Process_committed AND Process_p_nom_mod > 0
     expression: Process_p <= Process_p_max_pu * Process_p_nom_mod * (Process_status - Process_maintenance_pu * Process_maintenance_status)
   Process_status_p_fixed_upper:
     description: >-
@@ -249,7 +261,7 @@ constraints:
       place, an explicit row as PyPSA writes it: one where the build is not
       modular, and the fixed build's whole count of modules where it is
     dims: [scenario, snapshot, process]
-    where: Process_committable AND NOT (Process_p_nom_extendable AND Process_p_nom_mod > 0) AND Process_active
+    where: Process_committed AND NOT (Process_p_nom_extendable AND Process_p_nom_mod > 0)
     expression: Process_status <= Process_modules_installed
   Process_start_up_p_fixed_upper:
     description: >-
@@ -257,7 +269,7 @@ constraints:
       place, an explicit row as PyPSA writes it: one where the build is not
       modular, and the fixed build's whole count of modules where it is
     dims: [scenario, snapshot, process]
-    where: Process_committable AND NOT (Process_p_nom_extendable AND Process_p_nom_mod > 0) AND Process_active
+    where: Process_committed AND NOT (Process_p_nom_extendable AND Process_p_nom_mod > 0)
     expression: Process_start_up <= Process_modules_installed
   Process_shut_down_p_fixed_upper:
     description: >-
@@ -265,20 +277,20 @@ constraints:
       place, an explicit row as PyPSA writes it: one where the build is not
       modular, and the fixed build's whole count of modules where it is
     dims: [scenario, snapshot, process]
-    where: Process_committable AND NOT (Process_p_nom_extendable AND Process_p_nom_mod > 0) AND Process_active
+    where: Process_committed AND NOT (Process_p_nom_extendable AND Process_p_nom_mod > 0)
     expression: Process_shut_down <= Process_modules_installed
   Process_status_p_nom_variable_upper:
     description: "`Process-status-p_nom-variable-upper` — a modular process is on only where a module is built"
     dims: [scenario, snapshot, process]
-    where: Process_committable AND Process_p_nom_extendable AND Process_p_nom_mod > 0 AND Process_active
+    where: Process_committed AND Process_p_nom_extendable AND Process_p_nom_mod > 0
     expression: Process_status <= Process_n_mod
   Process_start_up_p_nom_variable_upper:
     description: "`Process-start_up-p_nom-variable-upper` — a modular process starts only where a module is built"
     dims: [scenario, snapshot, process]
-    where: Process_committable AND Process_p_nom_extendable AND Process_p_nom_mod > 0 AND Process_active
+    where: Process_committed AND Process_p_nom_extendable AND Process_p_nom_mod > 0
     expression: Process_start_up <= Process_n_mod
   Process_shut_down_p_nom_variable_upper:
     description: "`Process-shut_down-p_nom-variable-upper` — a modular process stops only where a module is built"
     dims: [scenario, snapshot, process]
-    where: Process_committable AND Process_p_nom_extendable AND Process_p_nom_mod > 0 AND Process_active
+    where: Process_committed AND Process_p_nom_extendable AND Process_p_nom_mod > 0
     expression: Process_shut_down <= Process_n_mod
diff --git a/examples/pypsa/process_maintenance.yaml b/examples/pypsa/process_maintenance.yaml
index af1beb1c..444353e6 100644
--- a/examples/pypsa/process_maintenance.yaml
+++ b/examples/pypsa/process_maintenance.yaml
@@ -75,9 +75,7 @@ variables:
       `Process-maintenance_capacity` — the chosen build while in maintenance, zero
       otherwise: the product the `maintcap` rows linearize
     dims: [scenario, snapshot, process]
-    where: >-
-      Process_maintainable AND Process_p_nom_extendable
-      AND NOT (Process_committable AND Process_p_nom_mod > 0) AND Process_active
+    where: Process_maint_ext
     absence: zero
     bounds:
       lower: 0
@@ -88,8 +86,9 @@ variables:
       maintenance may also be off
     dims: [scenario, snapshot, process]
     where: >-
-      Process_maintainable AND Process_committable
-      AND NOT (Process_p_nom_extendable AND NOT (Process_p_nom_mod > 0)) AND Process_active
+      Process_maintainable
+      AND Process_committed
+      AND NOT (Process_p_nom_extendable AND NOT (Process_p_nom_mod > 0))
     absence: zero
     bounds:
       lower: 0
@@ -106,6 +105,20 @@ given:
   variables:
     Process_status: { dims: [scenario, snapshot, process], domain: integer }
     Process_p_nom_ext: { dims: [process] }
+  masks:
+    Process_committed: { dims: [snapshot, process] }
+
+masks:
+  Process_maint_ext:
+    description: >-
+      a maintainable process with an extendable build, unless it is
+      committable and modular, that stands in the snapshot's period — the
+      maintenance rows against the chosen build
+    where: >-
+      Process_maintainable
+      AND Process_p_nom_extendable
+      AND NOT (Process_committable AND Process_p_nom_mod > 0)
+      AND Process_active
 
 constraints:
   Process_maint_event_count:
@@ -131,54 +144,54 @@ constraints:
       `Process-maintcap_upper` — the build taken off is at most the chosen build in
       maintenance, and at most the build less its floor out of it
     dims: [scenario, snapshot, process]
-    where: Process_maintainable AND Process_p_nom_extendable AND NOT (Process_committable AND Process_p_nom_mod > 0) AND Process_active
+    where: Process_maint_ext
     expression: Process_maintenance_capacity <= Process_p_nom_ext - Process_p_nom_min * (1 - Process_maintenance)
   Process_maintcap_upper_nommax:
     description: "`Process-maintcap_upper_nommax` — out of maintenance, no build is taken off"
     dims: [scenario, snapshot, process]
-    where: Process_maintainable AND Process_p_nom_extendable AND NOT (Process_committable AND Process_p_nom_mod > 0) AND Process_active
+    where: Process_maint_ext
     expression: Process_maintenance_capacity <= Process_p_nom_max * Process_maintenance
   Process_maintcap_lower_nommax:
     description: "`Process-maintcap_lower_nommax` — in maintenance, the whole chosen build is taken off"
     dims: [scenario, snapshot, process]
-    where: Process_maintainable AND Process_p_nom_extendable AND NOT (Process_committable AND Process_p_nom_mod > 0) AND Process_active
+    where: Process_maint_ext
     expression: Process_maintenance_capacity >= Process_p_nom_ext - Process_p_nom_max * (1 - Process_maintenance)
   Process_maintcap_lower_nommin:
     description: "`Process-maintcap_lower_nommin` — in maintenance, at least the floor of the build is taken off"
     dims: [scenario, snapshot, process]
-    where: Process_maintainable AND Process_p_nom_extendable AND NOT (Process_committable AND Process_p_nom_mod > 0) AND Process_active AND Process_p_nom_min > 0
+    where: Process_maint_ext AND Process_p_nom_min > 0
     expression: Process_maintenance_capacity >= Process_p_nom_min * Process_maintenance
   Process_maint_status_le_status:
     description: "`Process-maint-status-le-status` — the status in maintenance is at most the status"
     dims: [scenario, snapshot, process]
-    where: Process_maintainable AND Process_committable AND NOT Process_p_nom_extendable AND NOT (Process_p_nom_mod > 0) AND Process_active
+    where: Process_maintainable AND Process_committed AND NOT Process_p_nom_extendable AND NOT (Process_p_nom_mod > 0)
     expression: Process_maintenance_status <= Process_status
   Process_maint_status_le_maint:
     description: "`Process-maint-status-le-maint` — out of maintenance, the status in maintenance is zero"
     dims: [scenario, snapshot, process]
-    where: Process_maintainable AND Process_committable AND NOT Process_p_nom_extendable AND NOT (Process_p_nom_mod > 0) AND Process_active
+    where: Process_maintainable AND Process_committed AND NOT Process_p_nom_extendable AND NOT (Process_p_nom_mod > 0)
     expression: Process_maintenance_status <= Process_maintenance
   Process_maint_status_lb:
     description: "`Process-maint-status-lb` — on and in maintenance, the status in maintenance is one"
     dims: [scenario, snapshot, process]
-    where: Process_maintainable AND Process_committable AND NOT Process_p_nom_extendable AND NOT (Process_p_nom_mod > 0) AND Process_active
+    where: Process_maintainable AND Process_committed AND NOT Process_p_nom_extendable AND NOT (Process_p_nom_mod > 0)
     expression: Process_maintenance_status >= Process_status + Process_maintenance - 1
   Process_maint_modstatus_le_status:
     description: "`Process-maint-modstatus-le-status` — the modules on in maintenance are at most the modules on"
     dims: [scenario, snapshot, process]
-    where: Process_maintainable AND Process_committable AND Process_p_nom_mod > 0 AND Process_active
+    where: Process_maintainable AND Process_committed AND Process_p_nom_mod > 0
     expression: Process_maintenance_status <= Process_status
   Process_maint_modstatus_le_maint:
     description: >-
       `Process-maint-modstatus-le-maint` — out of maintenance, no module is on in
       maintenance; in it, at most the modules the build cap holds
     dims: [scenario, snapshot, process]
-    where: Process_maintainable AND Process_committable AND Process_p_nom_mod > 0 AND Process_active
+    where: Process_maintainable AND Process_committed AND Process_p_nom_mod > 0
     expression: Process_maintenance_status <= Process_p_nom_max / Process_p_nom_mod * Process_maintenance
   Process_maint_modstatus_lb:
     description: "`Process-maint-modstatus-lb` — in maintenance, every module on is on in maintenance"
     dims: [scenario, snapshot, process]
-    where: Process_maintainable AND Process_committable AND Process_p_nom_mod > 0 AND Process_active
+    where: Process_maintainable AND Process_committed AND Process_p_nom_mod > 0
     expression: Process_maintenance_status >= Process_status - Process_p_nom_max / Process_p_nom_mod * (1 - Process_maintenance)
 
 assumptions:
diff --git a/examples/pypsa/process_ramping.yaml b/examples/pypsa/process_ramping.yaml
index af2e36e6..7fb3d216 100644
--- a/examples/pypsa/process_ramping.yaml
+++ b/examples/pypsa/process_ramping.yaml
@@ -60,6 +60,8 @@ given:
     Process_p_nom_effective: { dims: [scenario, process] }
     Process_previous_status: { dims: [scenario, snapshot, process] }
     Process_p_nom_committed: { dims: [scenario, process] }
+  masks:
+    Process_com_ext: { dims: [snapshot, process] }
 
 expressions:
   Process_previous_p:
@@ -132,6 +134,16 @@ expressions:
           * (Process_previous_status - Process_status)
     otherwise: Process_ramp_down_rate * Process_p_nom_effective
 
+masks:
+  Process_ramps_from_previous:
+    description: >-
+      a snapshot whose ramp reads a previous output — any snapshot but its
+      period's first, and the horizon's first where the process comes in off
+      or carries an initial output
+    where: >-
+      position(snapshot, within=snapshot_period[period]) > 0 OR (position(snapshot) == 0 AND
+      (Process_status_initial == 0 OR Process_p_init))
+
 constraints:
   Process_p_ramp_limit_up_run_big_m:
     description: >-
@@ -139,11 +151,7 @@ constraints:
       raises internal power no faster than its limit of the chosen build; the big M
       releases the row in the snapshot it turns on
     dims: [scenario, snapshot, process]
-    where: >-
-      Process_committable AND Process_p_nom_extendable AND NOT (Process_p_nom_mod > 0)
-      AND (Process_ramp_limit_up OR Process_ramp_limit_start_up)
-      AND (position(snapshot, within=snapshot_period[period]) > 0 OR (position(snapshot) == 0 AND (Process_status_initial == 0 OR Process_p_init)))
-      AND Process_active
+    where: Process_com_ext AND (Process_ramp_limit_up OR Process_ramp_limit_start_up) AND Process_ramps_from_previous
     expression: >-
       Process_p - Process_previous_p <=
       Process_ramp_up_rate * Process_p_nom_ext
@@ -154,11 +162,7 @@ constraints:
       committed extendable process ramps no further than its start-up ramp of
       the chosen build; the big M releases the row everywhere else
     dims: [scenario, snapshot, process]
-    where: >-
-      Process_committable AND Process_p_nom_extendable AND NOT (Process_p_nom_mod > 0)
-      AND (Process_ramp_limit_up OR Process_ramp_limit_start_up)
-      AND (position(snapshot, within=snapshot_period[period]) > 0 OR (position(snapshot) == 0 AND (Process_status_initial == 0 OR Process_p_init)))
-      AND Process_active
+    where: Process_com_ext AND (Process_ramp_limit_up OR Process_ramp_limit_start_up) AND Process_ramps_from_previous
     expression: >-
       Process_p - Process_previous_p <=
       Process_start_up_rate * Process_p_nom_ext
@@ -170,10 +174,9 @@ constraints:
       releases the row in the snapshot it turns off
     dims: [scenario, snapshot, process]
     where: >-
-      Process_committable AND Process_p_nom_extendable AND NOT (Process_p_nom_mod > 0)
+      Process_com_ext
       AND (Process_ramp_limit_down OR Process_ramp_limit_shut_down)
-      AND (position(snapshot, within=snapshot_period[period]) > 0 OR (position(snapshot) == 0 AND (Process_status_initial == 0 OR Process_p_init)))
-      AND Process_active
+      AND Process_ramps_from_previous
     expression: >-
       Process_previous_p - Process_p <=
       Process_ramp_down_rate * Process_p_nom_ext
@@ -185,10 +188,9 @@ constraints:
       the chosen build; the big M releases the row everywhere else
     dims: [scenario, snapshot, process]
     where: >-
-      Process_committable AND Process_p_nom_extendable AND NOT (Process_p_nom_mod > 0)
+      Process_com_ext
       AND (Process_ramp_limit_down OR Process_ramp_limit_shut_down)
-      AND (position(snapshot, within=snapshot_period[period]) > 0 OR (position(snapshot) == 0 AND (Process_status_initial == 0 OR Process_p_init)))
-      AND Process_active
+      AND Process_ramps_from_previous
     expression: >-
       Process_previous_p - Process_p <=
       Process_shut_down_rate * Process_p_nom_ext
@@ -205,7 +207,7 @@ constraints:
     where: >-
       (Process_ramp_limit_up OR Process_ramp_limit_start_up)
       AND NOT (Process_committable AND Process_p_nom_extendable AND NOT (Process_p_nom_mod > 0))
-      AND (position(snapshot, within=snapshot_period[period]) > 0 OR (position(snapshot) == 0 AND (Process_status_initial == 0 OR Process_p_init)))
+      AND Process_ramps_from_previous
       AND Process_active
     expression: Process_p - Process_previous_p <= Process_ramp_up_allowance
   Process_p_ramp_limit_down:
@@ -220,7 +222,7 @@ constraints:
     where: >-
       (Process_ramp_limit_down OR Process_ramp_limit_shut_down)
       AND NOT (Process_committable AND Process_p_nom_extendable AND NOT (Process_p_nom_mod > 0))
-      AND (position(snapshot, within=snapshot_period[period]) > 0 OR (position(snapshot) == 0 AND (Process_status_initial == 0 OR Process_p_init)))
+      AND Process_ramps_from_previous
       AND Process_active
     expression: Process_previous_p - Process_p <= Process_ramp_down_allowance
 
diff --git a/examples/pypsa/storage_unit.yaml b/examples/pypsa/storage_unit.yaml
index d5118e1b..d838e891 100644
--- a/examples/pypsa/storage_unit.yaml
+++ b/examples/pypsa/storage_unit.yaml
@@ -316,70 +316,82 @@ expressions:
       sum(StorageUnit_sign * (StorageUnit_p_dispatch - StorageUnit_p_store), over=storage_unit, by=StorageUnit_bus[bus])
     adds_to: Bus_injection
 
+masks:
+  StorageUnit_fix:
+    description: >-
+      a storage unit with a fixed build that stands in the snapshot's period —
+      PyPSA's `fix` rows
+    where: NOT StorageUnit_p_nom_extendable AND StorageUnit_active
+  StorageUnit_ext:
+    description: >-
+      a storage unit with an extendable build that stands in the snapshot's
+      period — PyPSA's `ext` rows
+    where: StorageUnit_p_nom_extendable AND StorageUnit_active
+
 constraints:
   StorageUnit_fix_p_dispatch_lower:
     description: "`StorageUnit-fix-p_dispatch-lower` — dispatch is non-negative"
     dims: [scenario, snapshot, storage_unit]
-    where: not StorageUnit_p_nom_extendable AND StorageUnit_active
+    where: StorageUnit_fix
     expression: StorageUnit_p_dispatch >= 0
   StorageUnit_fix_p_dispatch_upper:
     description: "`StorageUnit-fix-p_dispatch-upper` — a fixed unit dispatches at most its nominal power"
     dims: [scenario, snapshot, storage_unit]
-    where: not StorageUnit_p_nom_extendable AND StorageUnit_active
+    where: StorageUnit_fix
     expression: StorageUnit_p_dispatch <= StorageUnit_p_max_pu * StorageUnit_p_nom
   StorageUnit_fix_p_store_lower:
     description: "`StorageUnit-fix-p_store-lower` — storing is non-negative"
     dims: [scenario, snapshot, storage_unit]
-    where: not StorageUnit_p_nom_extendable AND StorageUnit_active
+    where: StorageUnit_fix
     expression: StorageUnit_p_store >= 0
   StorageUnit_fix_p_store_upper:
     description: >-
       `StorageUnit-fix-p_store-upper` — a fixed unit stores at most its
       nominal power, the minimum-per-unit column carrying that cap negated
     dims: [scenario, snapshot, storage_unit]
-    where: not StorageUnit_p_nom_extendable AND StorageUnit_active
+    where: StorageUnit_fix
     expression: StorageUnit_p_store <= -StorageUnit_p_min_pu * StorageUnit_p_nom
   StorageUnit_fix_state_of_charge_lower:
     description: "`StorageUnit-fix-state_of_charge-lower` — charge is non-negative"
     dims: [scenario, snapshot, storage_unit]
-    where: not StorageUnit_p_nom_extendable AND StorageUnit_active
+    where: StorageUnit_fix
     expression: StorageUnit_state_of_charge >= 0
   StorageUnit_fix_state_of_charge_upper:
     description: "`StorageUnit-fix-state_of_charge-upper` — a fixed unit holds at most its hours at nominal power"
     dims: [scenario, snapshot, storage_unit]
-    where: not StorageUnit_p_nom_extendable AND StorageUnit_active
+    where: StorageUnit_fix
     expression: StorageUnit_state_of_charge <= StorageUnit_max_hours * StorageUnit_p_nom
   StorageUnit_ext_p_dispatch_lower:
     description: "`StorageUnit-ext-p_dispatch-lower` — dispatch is non-negative"
     dims: [scenario, snapshot, storage_unit]
-    where: StorageUnit_p_nom_extendable AND StorageUnit_active
+    where: StorageUnit_ext
     expression: StorageUnit_p_dispatch >= 0
   StorageUnit_ext_p_dispatch_upper:
     description: "`StorageUnit-ext-p_dispatch-upper` — an extendable unit dispatches at most the chosen build"
     dims: [scenario, snapshot, storage_unit]
-    where: StorageUnit_p_nom_extendable AND StorageUnit_active
+    where: StorageUnit_ext
     expression: StorageUnit_p_dispatch <= StorageUnit_p_max_pu * StorageUnit_p_nom_ext
   StorageUnit_ext_p_store_lower:
     description: "`StorageUnit-ext-p_store-lower` — storing is non-negative"
     dims: [scenario, snapshot, storage_unit]
-    where: StorageUnit_p_nom_extendable AND StorageUnit_active
+    where: StorageUnit_ext
     expression: StorageUnit_p_store >= 0
   StorageUnit_ext_p_store_upper:
     description: >-
       `StorageUnit-ext-p_store-upper` — an extendable unit stores at most the
       chosen build, the minimum-per-unit column carrying that cap negated
     dims: [scenario, snapshot, storage_unit]
-    where: StorageUnit_p_nom_extendable AND StorageUnit_active
+    where: StorageUnit_ext
     expression: StorageUnit_p_store <= -StorageUnit_p_min_pu * StorageUnit_p_nom_ext
   StorageUnit_ext_state_of_charge_lower:
     description: "`StorageUnit-ext-state_of_charge-lower` — charge is non-negative"
     dims: [scenario, snapshot, storage_unit]
-    where: StorageUnit_p_nom_extendable AND StorageUnit_active
+    where: StorageUnit_ext
     expression: StorageUnit_state_of_charge >= 0
   StorageUnit_ext_state_of_charge_upper:
     description: "`StorageUnit-ext-state_of_charge-upper` — an extendable unit holds at most its hours at the chosen build"
     dims: [scenario, snapshot, storage_unit]
-    where: StorageUnit_p_nom_extendable AND StorageUnit_active
+    where: StorageUnit_ext
     expression: StorageUnit_state_of_charge <= StorageUnit_max_hours * StorageUnit_p_nom_ext
   StorageUnit_ext_p_nom_lower:
     description: "`StorageUnit-ext-p_nom-lower` — the chosen build is at least its floor in every scenario"
diff --git a/examples/pypsa/transformer.yaml b/examples/pypsa/transformer.yaml
index 24400869..88f8b3c0 100644
--- a/examples/pypsa/transformer.yaml
+++ b/examples/pypsa/transformer.yaml
@@ -176,7 +176,7 @@ variables:
       a line does; absent, and zero in the balance, where the network is
       lossless
     dims: [scenario, snapshot, transformer]
-    where: transmission_losses AND Transformer_active
+    where: Transformer_lossy
     absence: zero
     bounds:
       lower: 0
@@ -239,6 +239,13 @@ expressions:
       + sum(Transformer_phase_shift * at(Transformer_phase_shift_cycle_weight, by=snapshot_period[period]), over=transformer)
     adds_to: Cycle_angle_sum
 
+masks:
+  Transformer_lossy:
+    description: >-
+      a transformer that stands in the snapshot's period, where the run models
+      transmission losses
+    where: transmission_losses AND Transformer_active
+
 constraints:
   Transformer_fix_s_lower:
     description: "`Transformer-fix-s-lower` — a fixed transformer carries at least the negative of its rating, the loss counted against it"
@@ -320,7 +327,7 @@ constraints:
   Transformer_loss_upper:
     description: "`Transformer-loss_upper` — a transformer dissipates at most the loss at its rating"
     dims: [scenario, snapshot, transformer]
-    where: transmission_losses AND Transformer_active
+    where: Transformer_lossy
     expression: Transformer_loss <= Transformer_loss_max
   Transformer_loss_tangents_forward:
     description: >-
@@ -328,12 +335,12 @@ constraints:
       loss sits above every cut to its curve for flow one way, as a line's
       does, over the segment dimension
     dims: [scenario, snapshot, transformer, segment]
-    where: transmission_losses AND Transformer_active
+    where: Transformer_lossy
     expression: Transformer_loss + Transformer_loss_slope * Transformer_s >= Transformer_loss_offset
   Transformer_loss_tangents_reverse:
     description: >-
       `Transformer-loss_tangents-{k}--1`, `Transformer-loss_secants-neg` — the
       same fan mirrored, the loss depending on the flow's magnitude
     dims: [scenario, snapshot, transformer, segment]
-    where: transmission_losses AND Transformer_active
+    where: Transformer_lossy
     expression: Transformer_loss - Transformer_loss_slope * Transformer_s >= Transformer_loss_offset
diff --git a/examples/symbols/pypsa.yaml b/examples/symbols/pypsa.yaml
index 45d80c05..3e4629c9 100644
--- a/examples/symbols/pypsa.yaml
+++ b/examples/symbols/pypsa.yaml
@@ -328,6 +328,22 @@ names:
   Line_active: '\mathrm{on}^{s}'
   Process_active: '\mathrm{on}^{z}'
   Transformer_active: '\mathrm{on}^{\sigma}'
+  Generator_committed: '\mathrm{on}^{\mathrm{com}}'
+  Generator_com_ext: '\mathrm{on}^{\mathrm{com,ext}}'
+  Generator_maint_ext: '\mathrm{on}^{\mathrm{mnt,ext}}'
+  Generator_ramps_from_previous: '\mathrm{prev}'
+  Link_committed: '\mathrm{on}^{f,\mathrm{com}}'
+  Link_com_ext: '\mathrm{on}^{f,\mathrm{com,ext}}'
+  Link_maint_ext: '\mathrm{on}^{f,\mathrm{mnt,ext}}'
+  Link_ramps_from_previous: '\mathrm{prev}^{f}'
+  Process_committed: '\mathrm{on}^{z,\mathrm{com}}'
+  Process_com_ext: '\mathrm{on}^{z,\mathrm{com,ext}}'
+  Process_maint_ext: '\mathrm{on}^{z,\mathrm{mnt,ext}}'
+  Process_ramps_from_previous: '\mathrm{prev}^{z}'
+  StorageUnit_fix: '\mathrm{on}^{h,\mathrm{fix}}'
+  StorageUnit_ext: '\mathrm{on}^{h,\mathrm{ext}}'
+  Line_lossy: '\mathrm{on}^{s,\mathrm{lossy}}'
+  Transformer_lossy: '\mathrm{on}^{\sigma,\mathrm{lossy}}'
   Generator_capital_weight: '\mathrm{W}'
   Link_capital_weight: '\mathrm{W}^{f}'
   StorageUnit_capital_weight: '\mathrm{W}^{h}'
diff --git a/mkdocs.yml b/mkdocs.yml
index 01b0df5b..1d4d4822 100644
--- a/mkdocs.yml
+++ b/mkdocs.yml
@@ -53,7 +53,7 @@ nav:
           - Dimensions: reference/language/dimensions.md
           - Relations: reference/language/relations.md
           - Expressions: reference/language/expressions.md
-          - Named expressions and macros: reference/language/named.md
+          - Named expressions, masks and macros: reference/language/named.md
           - Operators: reference/language/operators.md
           - Piecewise curves and SOS: reference/language/piecewise.md
           - Assumptions: reference/language/assumptions.md
diff --git a/schema/mathspec.schema.json b/schema/mathspec.schema.json
index 4016f4be..35de691f 100644
--- a/schema/mathspec.schema.json
+++ b/schema/mathspec.schema.json
@@ -289,7 +289,7 @@
     },
     "GivenBlock": {
       "additionalProperties": false,
-      "description": "What this file reads and does not build, by kind. Closed at the four kinds.",
+      "description": "What this file reads and does not build, by kind. Closed at the five kinds.",
       "properties": {
         "constraints": {
           "additionalProperties": {
@@ -307,6 +307,14 @@
           "title": "Expressions",
           "type": "object"
         },
+        "masks": {
+          "additionalProperties": {
+            "$ref": "#/$defs/GivenMaskBlock"
+          },
+          "default": {},
+          "title": "Masks",
+          "type": "object"
+        },
         "parameters": {
           "additionalProperties": {
             "$ref": "#/$defs/GivenParameterBlock"
@@ -387,6 +395,36 @@
       "title": "GivenExpressionBlock",
       "type": "object"
     },
+    "GivenMaskBlock": {
+      "additionalProperties": false,
+      "description": "A mask this file reads and another file defines.\n\nThe frame is all this file states, and it names the dims the definer's\npredicate reads. A where reads the name as data over that frame, true or false at each coordinate, since a mask reads nothing\na solve decides: the predicate is the definer's.",
+      "properties": {
+        "description": {
+          "anyOf": [
+            {
+              "type": "string"
+            },
+            {
+              "type": "null"
+            }
+          ],
+          "default": null,
+          "title": "Description"
+        },
+        "dims": {
+          "items": {
+            "type": "string"
+          },
+          "title": "Dims",
+          "type": "array"
+        }
+      },
+      "required": [
+        "dims"
+      ],
+      "title": "GivenMaskBlock",
+      "type": "object"
+    },
     "GivenParameterBlock": {
       "additionalProperties": false,
       "description": "Data this file reads and another file declares.\n\nIt says what a [`ParameterBlock`][] says, because the frame and the\ndtype are all a parameter declaration holds: a where compares against the\ndtype, and the dim rules read the frame.",
@@ -511,6 +549,40 @@
       "title": "MacroBlock",
       "type": "object"
     },
+    "MaskBlock": {
+      "anyOf": [
+        {
+          "additionalProperties": false,
+          "description": "A named predicate: one where string, read wherever a ``where:``, a ``when:`` or a ``holds:`` names it.\n\nWritten in YAML as a bare where string, or as a mapping once it carries a\n``description:``, and serialised back to whichever form it was written in::\n\n    masks:\n      committable: \"Generator_committable AND Generator_active\"\n      stands:\n        where: build_year <= period_year AND period_year < build_year + lifetime\n        description: the generator stands in this period\n\nA bare mask name in a where string stands for its predicate, inside\n``count``, ``shift`` and ``at`` too. The mask's frame is the dims its\npredicate reads, so it declares none. A mask is a predicate, so it is\nnever a value in an expression.",
+          "properties": {
+            "description": {
+              "anyOf": [
+                {
+                  "type": "string"
+                },
+                {
+                  "type": "null"
+                }
+              ],
+              "default": null,
+              "title": "Description"
+            },
+            "where": {
+              "title": "Where",
+              "type": "string"
+            }
+          },
+          "required": [
+            "where"
+          ],
+          "title": "MaskBlock",
+          "type": "object"
+        },
+        {
+          "type": "string"
+        }
+      ]
+    },
     "ObjectiveBlock": {
       "additionalProperties": false,
       "description": "A declared objective function.",
@@ -879,7 +951,7 @@
   },
   "$schema": "https://json-schema.org/draft/2020-12/schema",
   "additionalProperties": false,
-  "description": "The declared math \u2014 one YAML file, or one dict, validated. Nothing here has seen data.\n\nA ``Spec`` that exists has passed the whole language: constructing one by\nany route \u2014 ``to_spec``, [`model_validate`][], the constructor \u2014 runs\nevery load-time check, expression pass included, and raises\n[`LanguageError`][] on a spec the language refuses.\nHolding one is the proof, so nothing downstream checks it again.\n\nThe API is the twelve declaration sections plus ``version`` and\n``description``, three ways back out \u2014 [`to_dict`][] for the spec as\ndata, [`to_yaml`][] for the file a reviewer reads, [`expand`][] for the\nspec with its formulations written out as plain rows \u2014 and [`program`][], the\nspec typed, which every reader after load walks. Everything else on this\nclass is pydantic's, not a contract this package keeps.",
+  "description": "The declared math \u2014 one YAML file, or one dict, validated. Nothing here has seen data.\n\nA ``Spec`` that exists has passed the whole language: constructing one by\nany route \u2014 ``to_spec``, [`model_validate`][], the constructor \u2014 runs\nevery load-time check, expression pass included, and raises\n[`LanguageError`][] on a spec the language refuses.\nHolding one is the proof, so nothing downstream checks it again.\n\nThe API is the thirteen declaration sections plus ``version`` and\n``description``, three ways back out \u2014 [`to_dict`][] for the spec as\ndata, [`to_yaml`][] for the file a reviewer reads, [`expand`][] for the\nspec with its formulations written out as plain rows \u2014 and [`program`][], the\nspec typed, which every reader after load walks. Everything else on this\nclass is pydantic's, not a contract this package keeps.",
   "properties": {
     "assumptions": {
       "additionalProperties": {
@@ -930,6 +1002,7 @@
       "default": {
         "constraints": {},
         "expressions": {},
+        "masks": {},
         "parameters": {},
         "variables": {}
       }
@@ -942,6 +1015,14 @@
       "title": "Macros",
       "type": "object"
     },
+    "masks": {
+      "additionalProperties": {
+        "$ref": "#/$defs/MaskBlock"
+      },
+      "default": {},
+      "title": "Masks",
+      "type": "object"
+    },
     "objective": {
       "anyOf": [
         {
diff --git a/src/mathspec/_expression_resolver.py b/src/mathspec/_expression_resolver.py
index b9343737..6b7d1f74 100644
--- a/src/mathspec/_expression_resolver.py
+++ b/src/mathspec/_expression_resolver.py
@@ -191,6 +191,9 @@ def _name(self, node: NameNode) -> Expression | None:
         """
         if node.name in self.formals:
             return None
+        if node.name in self.ns.masks or node.name in self.ns.given_masks:
+            self.errors.append(mask_compared(node.name, self.context))
+            return None
         if node.name in self.ns.bodies:
             try:
                 return cast('Expression', self.ns.named(node.name, self.context))
@@ -790,6 +793,14 @@ def _vacates(offset: int | str) -> bool:
     return offset != 0
 
 
+def mask_compared(name: str, context: str) -> str:
+    """The refusal for a mask written where a number goes: a side of a comparison, or arithmetic."""
+    return (
+        f"{context}: '{name}' is a mask, which is true or false where it is read, and not a number. "
+        f'Write it bare in the where — {name}, or NOT {name} — rather than comparing it or computing with it.'
+    )
+
+
 def _named_offset_edge_message(name: str) -> str:
     """Why a named offset must say what the vacated positions contribute.
 
diff --git a/src/mathspec/_where_resolver.py b/src/mathspec/_where_resolver.py
index d3c95689..8fb2f08a 100644
--- a/src/mathspec/_where_resolver.py
+++ b/src/mathspec/_where_resolver.py
@@ -26,7 +26,7 @@
     literal_number,
     nodes,
 )
-from mathspec._expression_resolver import ExpressionResolver
+from mathspec._expression_resolver import ExpressionResolver, mask_compared
 from mathspec._where_parser import (
     ColumnNode,
     UnresolvedComparisonNode,
@@ -35,7 +35,7 @@
     UnresolvedWhereNode,
 )
 from mathspec.dimensions import dims_of, join_dims
-from mathspec.errors import DimensionError, LanguageError, did_you_mean, prefixed, unordered
+from mathspec.errors import DimensionError, LanguageError, SchemaError, did_you_mean, prefixed, unordered
 from mathspec.expansion import expand
 from mathspec.program import (
     Add,
@@ -51,6 +51,7 @@
     JoinedPredicate,
     Mask,
     Multiply,
+    NamedMask,
     Negate,
     Not,
     Or,
@@ -108,7 +109,7 @@ def _expressions(self) -> ExpressionResolver:
 
     def where(self, node: Predicate | UnresolvedWhereNode) -> Predicate | UnresolvedWhereNode:
         """One predicate node typed, or returned unresolved with its refusal appended."""
-        if isinstance(node, BooleanLiteral | TypedPredicate):
+        if isinstance(node, BooleanLiteral | TypedPredicate | NamedMask):
             return node
         if isinstance(node, NameNode):
             return self._where_name(node)
@@ -126,13 +127,24 @@ def where(self, node: Predicate | UnresolvedWhereNode) -> Predicate | Unresolved
             return Or(self._child(node.left), self._child(node.right))
         assert_never(node)
 
+    @property
+    def masks(self) -> frozenset[str]:
+        """Every mask this file names, defined or given."""
+        return self.ns.masks | self.ns.given_masks
+
     def _child(self, node: Predicate | UnresolvedWhereNode) -> Predicate:
         """A connective's child, typed as resolved: an unresolved one survives only with its refusal appended."""
         return cast('Predicate', self.where(node))
 
     def _where_name(self, node: NameNode) -> Predicate | UnresolvedWhereNode:
-        """A bare name: a parameter's or relation's definedness, or a variable's existence."""
+        """A bare name: a mask's predicate, a parameter's or relation's definedness, or a variable's existence."""
         ns, context = self.ns, self.context
+        if node.name in ns.masks:
+            try:
+                return ns.mask(node.name, context)
+            except SchemaError as e:
+                self.errors.append(str(e))
+                return node
         kind = ns.kind(node.name)
         if kind is None:
             self.errors.append(ns.unknown(node.name, context, allow_dims=True))
@@ -304,6 +316,10 @@ def _comparison(self, node: UnresolvedComparisonNode) -> Predicate | UnresolvedW
         """
         if isinstance(node.left, FunctionCallNode) and node.left.name == 'position':
             return self._position(node.left, node)
+        compared = [name for side in (node.left, node.right) if (name := _side_name_or_none(side)) is not None]
+        if masked := [name for name in compared if name in self.masks]:
+            self.errors.append(mask_compared(masked[0], self.context))
+            return node
         plain = self._plain(node)
         if plain is None:
             return self._expression_comparison(node)
@@ -614,6 +630,11 @@ class _Plain(NamedTuple):
     quoted: bool
 
 
+def _side_name_or_none(side: ArithmeticNode | ColumnNode | KeywordNode) -> str | None:
+    """The bare name a side spells, or ``None`` — a quoted label is no name."""
+    return side.name if isinstance(side, NameNode) else None
+
+
 def _side_name(side: ArithmeticNode | ColumnNode) -> str | None:
     """The name a side of a where-comparison spells — bare or ``relation[column]`` — or ``None`` where it is arithmetic."""
     if isinstance(side, NameNode):
diff --git a/src/mathspec/advising.py b/src/mathspec/advising.py
index 9f8ffbac..ccb7092a 100644
--- a/src/mathspec/advising.py
+++ b/src/mathspec/advising.py
@@ -69,6 +69,7 @@ def _given(program: Program) -> list[Advice]:
             for name in given.expressions
         ),
         *(Advice('given', name, _given_note('row family', name)) for name in given.constraints),
+        *(Advice('given', name, _given_note('mask', name)) for name in given.masks),
     ]
 
 
diff --git a/src/mathspec/composition.py b/src/mathspec/composition.py
index 77047cd0..d6968068 100644
--- a/src/mathspec/composition.py
+++ b/src/mathspec/composition.py
@@ -47,8 +47,9 @@
   reads its own sum through another fragment is refused, both named.
 * **A given declaration is folded** into the declaration that introduces the
   name, once the reader is checked to say the same as the introducer or less.
-  A given expression's body may carry no dimension its reader does not state,
-  and a name read as one kind and introduced as another is refused. A
+  A given expression's body may carry no dimension its reader does not
+  state. A given mask states exactly the dims its definer's predicate reads.
+  A name read as one kind and introduced as another is refused. A
   reader's description fills a declaration its owner left undescribed.
   Two fragments that both read a name have to read it over one frame, as a
   set. What no fragment introduces stays under ``given:`` until a host model
@@ -121,6 +122,7 @@
     'variables': 'given variable',
     'constraints': 'given constraint',
     'expressions': 'given expression',
+    'masks': 'given mask',
 }
 
 #: What a fragment, a base or a patch may be given as.
@@ -588,21 +590,25 @@ def _fits(
     """Refuse a reading that says more than the declaration it folds into.
 
     A reading states the frame its introducer declares, and every other field
-    it writes is the introducer's. A given expression is the one kind whose
-    frame may be wider than the composed body: a body over fewer dimensions
-    broadcasts, and the composed load refuses a row it would repeat.
+    it writes is the introducer's. A mask declares no frame, so its reader
+    states the dims the predicate reads. A given expression is the one kind
+    whose frame may be wider than the composed body: a body over fewer
+    dimensions broadcasts, and the composed load refuses a row it would repeat.
     """
     stated = set(cast('list[str]', _mapping(reading)['dims']))
     if kind == 'expressions':
         frame = set(_definer_frame(loaded, key))
         fits = frame <= stated
+    elif kind == 'masks':
+        frame = set(next(spec.program.masks[key].dims for spec in loaded.values() if key in spec.program.masks))
+        fits = frame == stated
     else:
         frame = set(cast('list[str]', _mapping(introduced)['dims']))
         fits = frame == stated
     fields = {f: v for f, v in _mapping(_claims(reading)).items() if f != 'dims'}
     if fits and all(_mapping(introduced).get(f) == v for f, v in fields.items()):
         return
-    how = f'over {sorted(frame)}' if kind == 'expressions' else f'as {introduced!r}'
+    how = f'over {sorted(frame)}' if kind in ('expressions', 'masks') else f'as {introduced!r}'
     raise LanguageError(
         f"fragment '{_reader_of(read, kind, key)}' reads the {GIVEN_KINDS[kind]} {key!r} as {reading!r}, where "
         f"'{_author_of(read, kind, key)}' introduces it {how}. A given declaration says the same as the "
@@ -624,7 +630,7 @@ def _definer_frame(loaded: Mapping[str, Spec], key: str) -> frozenset[str]:
     return frozenset(frame)
 
 
-READ_KINDS = ('parameters', 'variables', 'expressions')
+READ_KINDS = ('parameters', 'variables', 'expressions', 'masks')
 
 
 def _same_kind(read: Mapping[str, dict[str, object]], merged: Mapping[str, object], kind: str, key: str) -> None:
diff --git a/src/mathspec/exclusivity.py b/src/mathspec/exclusivity.py
index d1ae8559..893b0cf5 100644
--- a/src/mathspec/exclusivity.py
+++ b/src/mathspec/exclusivity.py
@@ -31,6 +31,7 @@
     ExpressionComparison,
     JoinedPredicate,
     Mask,
+    NamedMask,
     Negate,
     Not,
     Or,
@@ -486,6 +487,8 @@ def _evaluate(node: Predicate, cell: dict[Subject, Cell], grid: _Grid) -> bool:
             return _evaluate(left, cell, grid) and _evaluate(right, cell, grid)
         case Or(left=left, right=right):
             return _evaluate(left, cell, grid) or _evaluate(right, cell, grid)
+        case NamedMask(body=body):
+            return _evaluate(body, cell, grid)
         case _:
             assert_never(node)
 
diff --git a/src/mathspec/lowering.py b/src/mathspec/lowering.py
index fdf18100..4ec69f24 100644
--- a/src/mathspec/lowering.py
+++ b/src/mathspec/lowering.py
@@ -32,6 +32,7 @@
     GivenTargets,
     Link,
     Mask,
+    MaskDeclaration,
     Named,
     ObjectiveDeclaration,
     Parameter,
@@ -51,6 +52,7 @@
     resolve_expression,
     resolve_expression_text,
     resolve_where_text,
+    self_existence,
 )
 from mathspec.validation import emitted_name_errors, reference_errors
 
@@ -128,9 +130,20 @@ def lower(schema: Spec) -> Program:
 
     terms = _terms(entries, schema, ns, errors)
 
+    masks: dict[str, MaskDeclaration] = {}
+    for mname, mdef in schema.masks.items():
+        named_mask, refusals = ns.mask_entry(mname)
+        errors.extend(refusals)
+        if named_mask is not None:
+            body = Mask(named_mask.body)
+            frame = tuple(d for d in schema.dimensions if d in body.dims)
+            masks[mname] = MaskDeclaration(body, frame, mdef.description)
+
     variables = {}
     for vname, vdef in schema.variables.items():
         where = resolve_where_text(vdef.where, ns, f"Variable '{vname}'", errors, self_variable=vname)
+        if where is not None and (refusal := self_existence(where, vname, f"Variable '{vname}'")) is not None:
+            errors.append(refusal)
         if vdef.domain == 'binary':
             lower_bound, upper_bound = Constant(0.0), Constant(1.0)
         else:
@@ -231,6 +244,7 @@ def lower(schema: Spec) -> Program:
             )
             for name, entry in entries.items()
         },
+        masks=masks,
         given=GivenTargets(
             parameters={
                 name: ParameterDeclaration(tuple(g.dims), g.dtype, g.description)
@@ -245,6 +259,7 @@ def lower(schema: Spec) -> Program:
             expressions={
                 name: GivenDeclaration(tuple(g.dims), g.description) for name, g in schema.given.expressions.items()
             },
+            masks={name: GivenDeclaration(tuple(g.dims), g.description) for name, g in schema.given.masks.items()},
         ),
         description=schema.description,
     )
diff --git a/src/mathspec/program.py b/src/mathspec/program.py
index 307a03bf..6ab7e62e 100644
--- a/src/mathspec/program.py
+++ b/src/mathspec/program.py
@@ -66,8 +66,10 @@
     'JoinedPredicate',
     'Link',
     'Mask',
+    'MaskDeclaration',
     'Multiply',
     'Named',
+    'NamedMask',
     'Negate',
     'Not',
     'ObjectiveDeclaration',
@@ -722,6 +724,9 @@ class GivenTargets:
     constraints: Mapping[str, GivenDeclaration] = Sealed({})
     #: Named expressions the host model defines, by name.
     expressions: Mapping[str, GivenDeclaration] = Sealed({})
+    #: Masks the host model defines, by name. A where reads one as the data it
+    #: is: a [`ParameterDefined`][] of a boolean over its frame.
+    masks: Mapping[str, GivenDeclaration] = Sealed({})
 
     def __post_init__(self) -> None:
         for f in fields(self):
@@ -729,7 +734,7 @@ def __post_init__(self) -> None:
 
     def __bool__(self) -> bool:
         """Whether the program reads anything it does not build."""
-        return bool(self.parameters or self.variables or self.constraints or self.expressions)
+        return bool(self.parameters or self.variables or self.constraints or self.expressions or self.masks)
 
 
 @dataclass(frozen=True)
@@ -798,6 +803,22 @@ class ExpressionDeclaration:
     adds_to: str | None = None
 
 
+@dataclass(frozen=True)
+class MaskDeclaration:
+    """A named predicate — a ``masks:`` entry, read wherever a ``where``, a ``when`` or a ``holds`` names it.
+
+    It builds nothing of its own: every use stands as a [`NamedMask`][] with
+    this predicate under it, so a consumer reading a mask never looks the
+    name up here.
+    """
+
+    where: Mask
+    #: The frame the mask is read over: the dims its predicate carries, in the
+    #: order ``dimensions:`` declares them.
+    dims: tuple[str, ...]
+    description: str | None = None
+
+
 @dataclass(frozen=True)
 class Link:
     """One link of a ``piecewise:`` block: an expression tied to the breakpoints a values parameter holds.
@@ -1023,6 +1044,9 @@ class Program:
     #: named expression is outside the language is refused by every verb that
     #: reads the file rather than only by the one that reads the expression.
     expressions: Mapping[str, ExpressionDeclaration] = Sealed({})
+    #: Declared ``masks:``. Each use stands as a [`NamedMask`][] where it is
+    #: read, so a consumer building rows needs nothing from this group.
+    masks: Mapping[str, MaskDeclaration] = Sealed({})
     #: What this program reads and does not build ([`GivenTargets`][]), for a host model to provide.
     given: GivenTargets = GivenTargets()
     #: What the file as a whole is, as its ``description:`` says.
@@ -1385,6 +1409,20 @@ class Or:
     right: Predicate
 
 
+@dataclass(frozen=True)
+class NamedMask:
+    """A use of a ``masks:`` entry, standing where its name was written, with the entry's predicate under it.
+
+    Its truth is its body's: a consumer steps through it, as
+    [`where_children`][] does. It is kept as a node rather than written in so
+    the typesetter can print the symbol where the name stood and define it
+    once, as [`Named`][] does for an expression.
+    """
+
+    name: str
+    body: Predicate
+
+
 #: Every predicate resolution has typed: it names a declaration and the kind is
 #: settled. Resolution passes these straight through, having nothing left to
 #: decide about them.
@@ -1403,20 +1441,21 @@ class Or:
     | JoinedPredicate
 )
 
-#: The boolean connectives — the only where nodes carrying other where nodes,
-#: and so the only place a walk over a predicate recurses. The grammar builds
-#: these classes directly, over leaves still unresolved, so a pre-resolution
-#: tree shares them — the transient impurity resolution normalizes away.
+#: The boolean connectives — with [`NamedMask`][], the only where nodes
+#: carrying other where nodes, and so the places a walk over a predicate
+#: recurses. The grammar builds these classes directly, over leaves still
+#: unresolved, so a pre-resolution tree shares them — the transient impurity
+#: resolution normalizes away.
 Connective = Not | And | Or
 
 #: Every resolved predicate node. The parser's ``Unresolved*`` nodes are not members: they live with the
 #: grammar in [`mathspec._where_parser`][], and resolution rewrites them away
 #: before anything here is asked.
-Predicate = BooleanLiteral | TypedPredicate | Connective
+Predicate = BooleanLiteral | TypedPredicate | Connective | NamedMask
 
 
 def where_children(where: Predicate) -> tuple[Predicate, ...]:
-    """The predicates under *where* — a connective's operands, and nothing under a leaf.
+    """The predicates under *where* — a connective's operands, a named mask's body, and nothing under a leaf.
 
     What every walk over a predicate recurses through, as [`children`][] is
     for an expression. A leaf has nothing under it whether or not it is
@@ -1426,6 +1465,8 @@ def where_children(where: Predicate) -> tuple[Predicate, ...]:
         return (where.operand,)
     if isinstance(where, (And, Or)):
         return (where.left, where.right)
+    if isinstance(where, NamedMask):
+        return (where.body,)
     return ()
 
 
@@ -1439,7 +1480,7 @@ def _atoms(where: Predicate) -> Iterator[TypedPredicate]:
     """
     if isinstance(where, TypedPredicate):
         yield where
-    elif isinstance(where, BooleanLiteral | Connective):
+    elif isinstance(where, BooleanLiteral | Connective | NamedMask):
         for child in where_children(where):
             yield from _atoms(child)
     else:
@@ -1556,7 +1597,8 @@ def _fold(node: Predicate) -> Predicate:
     none, ``NOT True`` is ``False`` and ``NOT NOT X`` is ``X``. What survives
     is a predicate over data, or the one literal the whole mask reduces to —
     the invariant [`Mask`][] applies at construction, so it holds wherever
-    a mask is built.
+    a mask is built. A [`NamedMask`][] is left whole: its body was folded
+    when the entry was read, and refused there where it folded to a literal.
     """
     if isinstance(node, Not):
         operand = _fold(node.operand)
diff --git a/src/mathspec/resolution.py b/src/mathspec/resolution.py
index 97c25001..9200d75e 100644
--- a/src/mathspec/resolution.py
+++ b/src/mathspec/resolution.py
@@ -41,9 +41,11 @@
     Expression,
     Mask,
     Named,
+    NamedMask,
     Predicate,
     Region,
     RelationDeclaration,
+    VariableDefined,
     carries_variable,
 )
 
@@ -53,7 +55,7 @@
     from mathspec._expression_parser import ComparisonOperator, ParsedNode
     from mathspec._where_parser import ParsedWhere
     from mathspec.program import DeclaredDtype
-    from mathspec.spec import ExpressionBlock, Spec
+    from mathspec.spec import ExpressionBlock, MaskBlock, Spec
 
 
 #: What a name a file may write turns out to be. Answered by
@@ -70,12 +72,15 @@ class Namespace:
 
     __slots__ = (
         '_loading',
+        '_masks',
         '_named',
         'bodies',
         'constraints',
         'dimensions',
         'dtypes',
+        'given_masks',
         'leaf_dims',
+        'masks',
         'parameters',
         'relations',
         'schema',
@@ -91,7 +96,12 @@ def __init__(self, schema: Spec) -> None:
         parameters = {**schema.parameters, **schema.given.parameters}
         self.variables = frozenset(variables)
         self.bodies = frozenset(schema.expressions)
-        self.parameters = frozenset(parameters)
+        #: The declared masks, read by name wherever a where string is.
+        self.masks = frozenset(schema.masks)
+        #: The masks this file reads under ``given:``. A where reads each as
+        #: the boolean data it is to this file, so each is a parameter here too.
+        self.given_masks = frozenset(schema.given.masks)
+        self.parameters = frozenset(parameters) | self.given_masks
         self.dimensions = frozenset(schema.dimensions)
         #: The declared constraint names, off the flat namespace: a bare name
         #: never reaches them, so a spec may name a constraint after a variable.
@@ -101,6 +111,7 @@ def __init__(self, schema: Spec) -> None:
         #: what a where comparison checks its literal against.
         self.dtypes: dict[str, DeclaredDtype] = {
             **{p: pd.dtype for p, pd in parameters.items()},
+            **{m: cast('DeclaredDtype', 'bool') for m in schema.given.masks},
             **{d: dd.dtype for d, dd in schema.dimensions.items()},
         }
         #: relation name -> its columns and key, as declared.
@@ -112,14 +123,18 @@ def __init__(self, schema: Spec) -> None:
         #: each leaf a where names, the way a relation leaf carries ``over``.
         self.leaf_dims: dict[str, tuple[str, ...]] = {
             **{p: tuple(pd.dims) for p, pd in parameters.items()},
+            **{m: tuple(md.dims) for m, md in schema.given.masks.items()},
             **{v: tuple(vd.dims or ()) for v, vd in variables.items()},
         }
         #: named expression -> its resolved node, or ``None``, and its refusals;
         #: filled the first time anything reads the name.
         self._named: dict[str, tuple[Named | None, tuple[str, ...]]] = {}
-        #: The named expressions waiting to be resolved, the one asked for
-        #: first — each above the entries it reads, so it is a cycle's chain.
+        #: The named expressions and masks waiting to be resolved, the one
+        #: asked for first — each above the entries it reads, so it is a cycle's chain.
         self._loading: list[str] = []
+        #: mask -> its resolved node, or ``None``, and its refusals; filled
+        #: the first time anything reads the name.
+        self._masks: dict[str, tuple[NamedMask | None, tuple[str, ...]]] = {}
 
     def named(self, name: str, context: str) -> Named:
         """The ``expressions:`` entry *name* as the node that stands where its name is written.
@@ -138,12 +153,39 @@ def named(self, name: str, context: str) -> Named:
             raise SchemaError(msg)
         return node
 
-    def cycle(self, name: str, context: str, through: Iterable[str] = ()) -> str | None:
+    def cycle(self, name: str, context: str, through: Iterable[str] = (), *, noun: str = 'expression') -> str | None:
         """The refusal for reading *name* while it is being resolved, or ``None``; *through* names the macros the read went through."""
         if name not in self._loading:
             return None
         chain = ' -> '.join([*self._loading[self._loading.index(name) :], *through, name])
-        return f'{context}: circular expression reference: {chain}'
+        return f'{context}: circular {noun} reference: {chain}'
+
+    def mask(self, name: str, context: str) -> NamedMask:
+        """The ``masks:`` entry *name* as the node that stands where its name is written.
+
+        Resolved under the entry's own context the first time it is asked
+        for, and read from then on, so a fault in it is reported once.
+
+        Raises:
+            SchemaError: The entry reads itself, or does not load.
+        """
+        if (refusal := self.cycle(name, context, noun='mask')) is not None:
+            raise SchemaError(refusal)
+        node, _ = self.mask_entry(name)
+        if node is None:
+            msg = f"{context}: mask '{name}' does not load. Its refusal is listed with it."
+            raise SchemaError(msg)
+        return node
+
+    def mask_entry(self, name: str) -> tuple[NamedMask | None, tuple[str, ...]]:
+        """The ``masks:`` entry *name* resolved, or ``None``, with every refusal it earned."""
+        if name not in self._masks:
+            self._loading.append(name)
+            errors: list[str] = []
+            node = _mask(name, self.schema.masks[name], self, errors)
+            self._loading.pop()
+            self._masks[name] = (node, tuple(errors))
+        return self._masks[name]
 
     def named_entry(self, name: str) -> tuple[Named | None, tuple[str, ...]]:
         """The ``expressions:`` entry *name* resolved, or ``None``, with every refusal it earned.
@@ -232,7 +274,12 @@ def unknown(self, name: str, context: str, *, allow_dims: bool, formals: Iterabl
         """
         shown: list[tuple[str, Iterable[str]]] = [('Formals', formals)] if formals else []
         shown += (
-            [('Parameters', self.parameters), ('Dimensions', self.dimensions), ('Relations', self.relations)]
+            [
+                ('Parameters', self.parameters),
+                ('Dimensions', self.dimensions),
+                ('Relations', self.relations),
+                *([('Masks', self.masks)] if self.masks else []),
+            ]
             if allow_dims
             else [('Variables', self.variables), ('Parameters', self.parameters)]
         )
@@ -467,6 +514,42 @@ def _named(name: str, block: ExpressionBlock, ns: Namespace, errors: list[str])
     return Named(name, Cases((*regions, left_over)))
 
 
+def _mask(name: str, block: MaskBlock, ns: Namespace, errors: list[str]) -> NamedMask | None:
+    """One ``masks:`` entry as the node every use of it holds, or ``None`` once anything in it failed.
+
+    A predicate the connectives decide is refused, since a name for every row
+    or for none narrows nothing a where could not say plainly.
+    """
+    context = f"Mask '{name}'"
+    body = resolve_where_text(block.where, ns, context, errors)
+    if body is None:
+        return None
+    if isinstance(body, BooleanLiteral):
+        errors.append(
+            f'{context}: the predicate {block.where!r} folds to {str(body.value).lower()}, so the mask '
+            f'{"admits every row" if body.value else "admits no row"} and names nothing a where needs. '
+            f'Delete it, or write the predicate over the data.'
+        )
+        return None
+    return NamedMask(name, body)
+
+
+def self_existence(where: Predicate, variable: str, context: str) -> str | None:
+    """The refusal for a variable whose own where asks, through a mask, whether it exists — or ``None``.
+
+    The where resolver refuses the bare name; a mask's predicate is resolved
+    under its own name, so the check runs again on the tree with every mask's
+    predicate in it.
+    """
+    if not any(isinstance(atom, VariableDefined) and atom.name == variable for atom in Mask(where).atoms):
+        return None
+    return (
+        f"{context}: variable '{variable}' asks whether it exists in its own where, through a mask, which "
+        f'nothing can answer — the mask is what decides where it exists. Test a parameter, or another '
+        f'variable declared before it.'
+    )
+
+
 def _constant_arm(context: str, *, value: bool) -> str:
     """The refusal for a case arm whose mask the connectives already decided.
 
diff --git a/src/mathspec/spec.py b/src/mathspec/spec.py
index b9398eed..098e7d99 100644
--- a/src/mathspec/spec.py
+++ b/src/mathspec/spec.py
@@ -361,8 +361,22 @@ class GivenExpressionBlock(_StrictBlock):
     description: str | None = None
 
 
+class GivenMaskBlock(_StrictBlock):
+    """A mask this file reads and another file defines.
+
+    The frame is all this file states, and it names the dims the definer's
+    predicate reads. A where reads the name as data over that frame, true or false at each coordinate, since a mask reads nothing
+    a solve decides: the predicate is the definer's.
+    """
+
+    _label: ClassVar[str] = 'a given mask declaration'
+
+    dims: list[str]
+    description: str | None = None
+
+
 class GivenBlock(_StrictBlock):
-    """What this file reads and does not build, by kind. Closed at the four kinds."""
+    """What this file reads and does not build, by kind. Closed at the five kinds."""
 
     _label: ClassVar[str] = 'a given block'
 
@@ -374,10 +388,12 @@ class GivenBlock(_StrictBlock):
     constraints: dict[str, GivenConstraintBlock] = {}
     #: Named expressions another file defines ([`GivenExpressionBlock`][]).
     expressions: dict[str, GivenExpressionBlock] = {}
+    #: Masks another file defines ([`GivenMaskBlock`][]).
+    masks: dict[str, GivenMaskBlock] = {}
 
     def __bool__(self) -> bool:
         """Whether the file reads anything it does not build."""
-        return bool(self.parameters or self.variables or self.constraints or self.expressions)
+        return bool(self.parameters or self.variables or self.constraints or self.expressions or self.masks)
 
 
 class ConstraintBlock(_StrictBlock):
@@ -567,6 +583,48 @@ def _as_written(self) -> str | dict[str, object]:
         return written
 
 
+class MaskBlock(_StrictBlock):
+    """A named predicate: one where string, read wherever a ``where:``, a ``when:`` or a ``holds:`` names it.
+
+    Written in YAML as a bare where string, or as a mapping once it carries a
+    ``description:``, and serialised back to whichever form it was written in::
+
+        masks:
+          committable: "Generator_committable AND Generator_active"
+          stands:
+            where: build_year <= period_year AND period_year < build_year + lifetime
+            description: the generator stands in this period
+
+    A bare mask name in a where string stands for its predicate, inside
+    ``count``, ``shift`` and ``at`` too. The mask's frame is the dims its
+    predicate reads, so it declares none. A mask is a predicate, so it is
+    never a value in an expression.
+    """
+
+    _label: ClassVar[str] = 'a mask declaration'
+
+    #: The predicate, in the where grammar.
+    where: str
+    description: str | None = None
+
+    @model_validator(mode='before')
+    @classmethod
+    def _from_string(cls, data: object) -> object:
+        return {'where': data} if isinstance(data, str) else data
+
+    @classmethod
+    @override
+    def __get_pydantic_json_schema__(cls, core_schema: CoreSchema, handler: GetJsonSchemaHandler) -> dict[str, object]:
+        """The published schema admits the bare string the one-line form is written as."""
+        return _also_written_as(core_schema, handler, {'type': 'string'})
+
+    @model_serializer
+    def _as_written(self) -> str | dict[str, object]:
+        if self.description is None:
+            return self.where
+        return {'where': self.where, 'description': self.description}
+
+
 class AssumptionBlock(_StrictBlock):
     """What the spec assumes of its data: a predicate every coordinate it is checked at has to satisfy.
 
@@ -825,7 +883,7 @@ class Spec(_StrictBlock):
     [`LanguageError`][] on a spec the language refuses.
     Holding one is the proof, so nothing downstream checks it again.
 
-    The API is the twelve declaration sections plus ``version`` and
+    The API is the thirteen declaration sections plus ``version`` and
     ``description``, three ways back out — [`to_dict`][] for the spec as
     data, [`to_yaml`][] for the file a reviewer reads, [`expand`][] for the
     spec with its formulations written out as plain rows — and [`program`][], the
@@ -852,6 +910,7 @@ class is pydantic's, not a contract this package keeps.
     constraints: dict[str, ConstraintBlock] = {}
     objective: ObjectiveBlock | None = None
     expressions: dict[str, ExpressionBlock] = {}
+    masks: dict[str, MaskBlock] = {}
     macros: dict[str, MacroBlock] = {}
     piecewise: dict[str, PiecewiseBlock] = {}
     sos: dict[str, SosBlock] = {}
@@ -995,7 +1054,7 @@ def _names_are_names(self) -> Spec:
 
         Read off the spec's own mappings rather than a list of sections, so a
         section added later cannot be forgotten here — every mapping a Spec
-        carries is keyed by a declaration name. ``given:`` nests its four
+        carries is keyed by a declaration name. ``given:`` nests its five
         mappings one level down, so they are read off [`GivenBlock`][] the
         same way.
         """
diff --git a/src/mathspec/typesetting/__init__.py b/src/mathspec/typesetting/__init__.py
index 6a85ebd8..ffe441de 100644
--- a/src/mathspec/typesetting/__init__.py
+++ b/src/mathspec/typesetting/__init__.py
@@ -176,8 +176,8 @@ def typeset_declaration(
     """Render one declaration as the bare line the document prints for it.
 
     The line the whole-spec render prints for it — a named expression's
-    definition, a constraint, an assumption, a ``piecewise:`` curve, or a
-    variable's domain, quantifier included —
+    or a mask's definition, a constraint, an assumption, a ``piecewise:``
+    curve, or a variable's domain, quantifier included —
     with no document, label, equation number or math delimiters around it, for
     a math context the caller lays out: a docstring, a table cell. A line on
     its own has no Definitions section beside it, so the plain named
@@ -186,8 +186,8 @@ def typeset_declaration(
 
     Args:
         spec: Anything [`mathspec.to_spec`][] accepts, or a [`Program`][].
-        name: A named expression, constraint, assumption, ``piecewise:``
-            block or variable the spec declares.
+        name: A named expression, mask, constraint, assumption,
+            ``piecewise:`` block or variable the spec declares.
         fmt: What spells the math — a key of [`FORMATS`][].
         symbols: How names print; see [`typeset`][].
         inline_expressions: Substitute the plain named expressions the line uses, so it
@@ -201,7 +201,7 @@ def typeset_declaration(
     Raises:
         ValueError: *fmt* names no format.
         LanguageError: A spec that does not compile; it does not print.
-        SchemaError: *name* is declared as none of the five, as two — a
+        SchemaError: *name* is declared as none of the six, as two — a
             constraint may share a variable's name — or under ``given:``, which
             prints in the legend rather than as a line; or a symbol table entry
             names nothing in the spec.
@@ -213,6 +213,7 @@ def typeset_declaration(
         'variable': given.variables,
         'expression': given.expressions,
         'constraint': given.constraints,
+        'mask': given.masks,
     }
     given_kind = next((kind for kind, group in givens.items() if name in group), None)
     if given_kind is not None:
diff --git a/src/mathspec/typesetting/format.py b/src/mathspec/typesetting/format.py
index fe888114..00193b6e 100644
--- a/src/mathspec/typesetting/format.py
+++ b/src/mathspec/typesetting/format.py
@@ -32,6 +32,7 @@
     'plus',
     'minus',
     'equal',
+    'iff',
     'le',
     'ge',
     'lt',
@@ -66,7 +67,8 @@
 
 #: Every operator a walk can emit, by the name the walk uses for it, with its
 #: LaTeX spelling first and its Typst spelling second — one row per operator,
-#: so no format can be missing one. ``such_that`` is the colon in
+#: so no format can be missing one. ``iff`` is the ⟺ a mask is defined
+#: with, since a predicate is not a value to equate. ``such_that`` is the colon in
 #: "∀ t ∈ T : condition", ``times`` sits between sets in the legend,
 #: ``maps_to`` is the → in a coordinate map, ``curve`` and ``hull`` are the two
 #: sets a ``piecewise:`` block states its links lie on, and the three
@@ -78,6 +80,7 @@
     'plus': ('+', '+'),
     'minus': ('-', '-'),
     'equal': ('=', '='),
+    'iff': (r'\iff', 'arrow.l.r.double.long'),
     'le': (r'\le', '<='),
     'ge': (r'\ge', '>='),
     'lt': ('<', '<'),
diff --git a/src/mathspec/typesetting/legend.py b/src/mathspec/typesetting/legend.py
index 5a7c0e1c..28d24451 100644
--- a/src/mathspec/typesetting/legend.py
+++ b/src/mathspec/typesetting/legend.py
@@ -111,6 +111,8 @@ def masks(mask: Mask) -> None:
         expressions(entry.expression)
     for curve in program.piecewise.values():
         expressions(*(link.expression for link in curve.links))
+    for mask in program.masks.values():
+        masks(mask.where)
     for declaration in (*program.constraints.values(), *program.variables.values()):
         if declaration.where is not None:
             masks(declaration.where)
@@ -133,7 +135,7 @@ def _op(self, name: OperatorName) -> str:
         return self.format.operators[name]
 
     def glossaries(self, noticed: Noticed, defined: Iterable[str]) -> list[tuple[str, list[Entry]]]:
-        """The sets, parameters, variables, given declarations and definitions, each with its symbol, its dims and its description.
+        """The sets, parameters, variables, given declarations, definitions and masks, each with its symbol, its dims and its description.
 
         *defined* names the expressions that print under their own symbol, so
         a legend row stands exactly where a symbol does.
@@ -189,6 +191,14 @@ def glossaries(self, noticed: Noticed, defined: Iterable[str]) -> list[tuple[str
                 )
                 for g, block in program.given.constraints.items()
             ),
+            *(
+                self._entry(
+                    self.symbols.name[g],
+                    f'{fmt.mono(g)}{self._over(list(block.dims))}, a mask another file defines',
+                    block.description,
+                )
+                for g, block in program.given.masks.items()
+            ),
         ]
         shown = set(defined)
         definitions = [
@@ -196,12 +206,17 @@ def glossaries(self, noticed: Noticed, defined: Iterable[str]) -> list[tuple[str
             for e, block in program.expressions.items()
             if e in shown
         ]
+        masks = [
+            self._entry(self.symbols.name[m], f'{fmt.mono(m)}{self._over(list(block.dims))}', block.description)
+            for m, block in program.masks.items()
+        ]
         groups = (
             ('Sets', sets),
             ('Parameters', parameters),
             ('Variables', variables),
             ('Given', given),
             ('Definitions', definitions),
+            ('Masks', masks),
         )
         return [(title, entries) for title, entries in groups if entries]
 
diff --git a/src/mathspec/typesetting/symbols.py b/src/mathspec/typesetting/symbols.py
index da15d756..30346672 100644
--- a/src/mathspec/typesetting/symbols.py
+++ b/src/mathspec/typesetting/symbols.py
@@ -104,7 +104,8 @@ class Symbols:
     Attributes:
         overridden: Names the table spelled; the convention note quotes only
             derived symbols.
-        name: Each parameter's, variable's and expression's symbol.
+        name: Each parameter's, variable's, expression's and mask's symbol.
+            A mask is upright, being read off the data as a parameter is.
         constraint: Each constraint's symbol, the subscript ``dual(c)`` prints
             λ against. Off the flat namespace, like the constraints themselves
             — a spec may name a constraint after a variable, so this is its
@@ -146,6 +147,8 @@ def symbols_for(program: Program, fmt: Format, table: SymbolTable) -> Symbols:
         *program.given.variables,
         *program.expressions,
         *program.given.expressions,
+        *program.masks,
+        *program.given.masks,
     )
     declared = frozenset(names)
 
@@ -291,6 +294,8 @@ def _declared(program: Program) -> set[str]:
         | set(program.given.variables)
         | set(program.expressions)
         | set(program.given.expressions)
+        | set(program.masks)
+        | set(program.given.masks)
         | set(program.constraints)
         | set(program.given.constraints)
     )
diff --git a/src/mathspec/typesetting/walk.py b/src/mathspec/typesetting/walk.py
index 11c2bf44..1e0aa369 100644
--- a/src/mathspec/typesetting/walk.py
+++ b/src/mathspec/typesetting/walk.py
@@ -35,6 +35,7 @@
     Mask,
     Multiply,
     Named,
+    NamedMask,
     Negate,
     Not,
     Or,
@@ -539,9 +540,12 @@ def _where(self, node: Predicate, ctx: _Context) -> tuple[str, int]:
             assert not node.value, 'an always-true mask is folded away or refused before anything prints it'
             return self._op('false'), _ATOM
 
+        if isinstance(node, NamedMask):
+            return ctx.indexed(self.symbols.name[node.name], list(self.program.masks[node.name].dims)), _ATOM
+
         if isinstance(node, ParameterDefined):
             indexed = ctx.indexed(self.symbols.name[node.name], list(node.dims))
-            if self._parameters[node.name].dtype == 'bool':
+            if node.name in self.program.given.masks or self._parameters[node.name].dtype == 'bool':
                 return indexed, _ATOM
             return f'{indexed} {self.format.prose(" is defined")}', comparison
 
@@ -664,6 +668,7 @@ def equations(self) -> list[tuple[str, list[Line]]]:
             ('Objective', self._objective()),
             ('Subject to', self._constraints()),
             ('Definitions', self._definitions()),
+            ('Masks', [self.mask(name) for name in self.program.masks]),
             ('Variable domains', self._variables()),
             ('Assumptions', self._assumptions()),
         ]
@@ -749,21 +754,38 @@ def definition(self, name: str) -> Line:
             condition=self._quantifier(frame, ''),
         )
 
+    def mask(self, name: str) -> Line:
+        """The line defining one mask, ``symbol ⟺ predicate`` over its frame.
+
+        A mask is a predicate rather than a value, so it is defined with ⟺
+        where an expression is defined with =; every use prints the symbol.
+        """
+        entry = self.program.masks[name]
+        frame = list(entry.dims)
+        ctx = self._context(frame)
+        return Line(
+            label=name,
+            left=ctx.indexed(self.symbols.name[name], frame),
+            right=f'{self._op("iff")} {self._predicate(entry.where.root, ctx)}',
+            condition=self._quantifier(frame, ''),
+        )
+
     def line(self, name: str) -> Line:
-        """The one line *name* prints as: a named expression, a constraint, an assumption, a curve, or a variable's domain.
+        """The one line *name* prints as: a named expression, a mask, a constraint, an assumption, a curve, or a variable's domain.
 
         An assumption is looked up where the document prints it from, so a
         condition a curve's method states is a line a reader can ask for
         before the curve is written out.
 
         Raises:
-            SchemaError: *name* is declared as none of the five, or as two — a
+            SchemaError: *name* is declared as none of the six, or as two — a
                 constraint may share a variable's name, and one line prints
                 one of them.
         """
         program = self.program
         kinds = {
             'named expression': (program.expressions, self.definition),
+            'mask': (program.masks, self.mask),
             'constraint': (program.constraints, self._constraint),
             'assumption': (program.assumptions, self._assumption),
             'curve': (program.piecewise, self._piecewise),
@@ -773,7 +795,7 @@ def line(self, name: str) -> Line:
         if not found:
             everything = {n for group, _ in kinds.values() for n in group}
             msg = (
-                f"'{name}' is not a named expression, constraint, assumption, curve or variable. "
+                f"'{name}' is not a named expression, mask, constraint, assumption, curve or variable. "
                 f'{did_you_mean(name, everything)}'
             )
             raise SchemaError(msg)
diff --git a/src/mathspec/validation.py b/src/mathspec/validation.py
index 32f3bc56..12b76bee 100644
--- a/src/mathspec/validation.py
+++ b/src/mathspec/validation.py
@@ -108,6 +108,8 @@ def _flat_namespace(schema: Spec) -> list[tuple[str, Iterable[str]]]:
         ('given variable', schema.given.variables),
         ('named expression', schema.expressions),
         ('given expression', schema.given.expressions),
+        ('mask', schema.masks),
+        ('given mask', schema.given.masks),
         ('macro', schema.macros),
     ]
 
@@ -155,6 +157,7 @@ def _frame_dimensions(schema: Spec) -> Iterator[str]:
         *(('Given variable', name, g.dims) for name, g in schema.given.variables.items()),
         *(('Given expression', name, g.dims) for name, g in schema.given.expressions.items()),
         *(('Given constraint', name, g.dims) for name, g in schema.given.constraints.items()),
+        *(('Given mask', name, g.dims) for name, g in schema.given.masks.items()),
         *(('Constraint', name, c.dims) for name, c in schema.constraints.items()),
         *(('Named expression', name, e.dims or []) for name, e in schema.expressions.items()),
     ]
diff --git a/tests/test_canonical.py b/tests/test_canonical.py
index 54edf0e3..c5d25364 100644
--- a/tests/test_canonical.py
+++ b/tests/test_canonical.py
@@ -149,6 +149,7 @@ def test_the_declarations_of_a_section_are_sorted_by_name():
     'constraints',
     'objective',
     'expressions',
+    'masks',
     'macros',
     'piecewise',
     'sos',
diff --git a/tests/test_given.py b/tests/test_given.py
index 732f1e93..ba355282 100644
--- a/tests/test_given.py
+++ b/tests/test_given.py
@@ -48,11 +48,11 @@
 }
 
 
-def test_given_holds_four_kinds_and_refuses_a_fifth():
+def test_given_holds_five_kinds_and_refuses_a_sixth():
     """The section is closed, so a kind nobody has admitted yet is the schema's own refusal."""
     with pytest.raises(LanguageError) as raised:
         to_spec({**SUPPLY, 'given': {'macros': {'twice': {'params': ['x'], 'template': '2 * x'}}}})
-    assert 'Valid keys: constraints, expressions, parameters, variables' in str(raised.value), (
+    assert 'Valid keys: constraints, expressions, masks, parameters, variables' in str(raised.value), (
         'the refusal names what the block takes'
     )
 
diff --git a/tests/test_masks.py b/tests/test_masks.py
new file mode 100644
index 00000000..4ea9a1f6
--- /dev/null
+++ b/tests/test_masks.py
@@ -0,0 +1,306 @@
+# SPDX-FileCopyrightText: mathspec Contributors
+#
+# SPDX-License-Identifier: MIT
+
+"""A mask is a named predicate: written once under ``masks:``, read by name wherever a where string is (#803).
+
+A use stands as a `NamedMask` with the predicate under it, so every question
+asked of a mask is asked of the predicate, and the typesetter still prints the
+name. Another file reads a mask under ``given: masks:`` as the boolean data it
+is to that file, and `merge` folds the reading into the definition.
+"""
+
+from __future__ import annotations
+
+import copy
+from typing import Any
+
+import pytest
+
+from mathspec import FORMATS, LanguageError, advice, merge, override, to_spec, typeset, typeset_declaration
+from mathspec.program import Mask, NamedMask, ParameterDefined, VariableDefined
+from tests.fixtures import SMALL_MODEL, varied
+
+#: A unit stands in a period between its build year and its retirement, and
+#: two families of rows read that test: the core's capacity and a ramp.
+DIMS: dict[str, Any] = {'period': {'dtype': 'int', 'ordered': True}, 'generator': {'dtype': 'str'}}
+FRAME = ['period', 'generator']
+STANDS = 'build_year <= period_year AND period_year < build_year + lifetime'
+
+CORE: dict[str, Any] = {
+    'dimensions': DIMS,
+    'parameters': {
+        'build_year': {'dims': ['generator']},
+        'lifetime': {'dims': ['generator']},
+        'period_year': {'dims': ['period']},
+        'p_nom': {'dims': ['generator']},
+    },
+    'masks': {'stands': {'where': STANDS, 'description': 'the unit stands in this period'}},
+    'variables': {'p': {'dims': FRAME, 'where': 'stands', 'bounds': {'lower': 0}}},
+    'constraints': {'cap': {'dims': FRAME, 'where': 'stands', 'expression': 'p <= p_nom'}},
+    'objective': {'sense': 'minimize', 'expression': 'sum(p, over=[period, generator])'},
+}
+
+RAMPING: dict[str, Any] = {
+    'dimensions': DIMS,
+    'given': {'variables': {'p': {'dims': FRAME}}, 'masks': {'stands': {'dims': FRAME}}},
+    'parameters': {'ramp': {'dims': ['generator']}},
+    'constraints': {
+        'ramp_up': {
+            'dims': FRAME,
+            'where': 'stands AND shift(stands, along=period, offset=1)',
+            'expression': 'p - shift(p, along=period, offset=1) <= ramp',
+        }
+    },
+}
+
+
+def test_a_mask_stands_where_its_name_is_written_with_its_predicate_under_it():
+    program = to_spec(CORE).program
+    where = program.constraints['cap'].where
+    assert where is not None and isinstance(where.root, NamedMask), 'the use keeps the name the file wrote'
+    assert where.root.body == program.masks['stands'].where.root, 'and carries the predicate the entry declares'
+    assert program.masks['stands'].dims == ('period', 'generator')
+    assert where.names_read == {'build_year', 'lifetime', 'period_year'}, 'a mask reads what its predicate reads'
+    assert where.dims == {'period', 'generator'}
+
+
+@pytest.mark.parametrize(
+    'patch',
+    [
+        pytest.param({'constraints.cap.where': 'NOT stands'}, id='under-a-connective'),
+        pytest.param({'constraints.cap.where': 'stands AND shift(stands, along=period, offset=1)'}, id='in-shift'),
+        pytest.param(
+            {'assumptions.lives': {'holds': 'lifetime > 0', 'where': 'stands'}}, id='as-an-assumption-s-where'
+        ),
+        pytest.param({'assumptions.ever': 'count(stands, over=period) >= 1'}, id='in-count'),
+        pytest.param(
+            {
+                'expressions.share': {
+                    'dims': FRAME,
+                    'cases': {'standing': {'when': 'stands', 'expression': 'p_nom'}},
+                    'otherwise': 0,
+                }
+            },
+            id='as-a-when',
+        ),
+        pytest.param({'masks.old': 'stands AND lifetime > 30', 'constraints.cap.where': 'old'}, id='in-another-mask'),
+        pytest.param(
+            {'expressions.half': 'p_nom / 2', 'masks.big': 'half > 10', 'constraints.cap.where': 'big'},
+            id='reading-a-data-only-expression',
+        ),
+        pytest.param({'masks.stands': STANDS}, id='the-one-line-form'),
+    ],
+)
+def test_a_mask_is_read_wherever_a_where_string_is(patch):
+    spec = to_spec(varied(CORE, **patch))
+    assert to_spec(spec.to_yaml()).program == spec.program, 'the file reads back to the same program'
+
+
+def test_the_one_line_form_writes_back_as_written():
+    spec = to_spec(varied(CORE, **{'masks.stands': STANDS}))
+    assert spec.to_dict()['masks'] == {'stands': STANDS}, 'a mask with no words is one where string'
+
+
+def test_a_mask_declares_no_frame():
+    """A declared frame wider than the predicate printed a use over an index no quantifier binds.
+
+    ``young`` over ``[period, generator]`` read only ``lifetime``. A use over
+    ``[generator]`` loaded, and every format printed ``young`` with a period
+    index under a quantifier over generators alone. The predicate gives a mask
+    its frame, so the closed schema now refuses ``dims:`` on a mask.
+    """
+    young = {
+        'masks.young': {'dims': FRAME, 'where': 'lifetime > 10'},
+        'constraints.total': {'dims': ['generator'], 'where': 'young', 'expression': 'sum(p, over=period) <= p_nom'},
+    }
+    with pytest.raises(LanguageError, match=r"masks\.young: unknown key 'dims' in a mask declaration"):
+        to_spec(varied(CORE, **young))
+
+
+def test_a_variable_that_asks_through_a_mask_whether_it_exists_is_refused():
+    """The where resolver refused the bare name only: a mask's predicate is read under the mask's own name."""
+    with pytest.raises(LanguageError, match=r"variable 'p' asks whether it exists in its own where, through a mask"):
+        to_spec(varied(CORE, **{'masks.live': 'p', 'variables.p.where': 'live'}))
+
+
+def test_a_mask_may_ask_whether_another_variable_exists():
+    spec = to_spec(varied(CORE, **{'masks.dispatched': 'p', 'constraints.cap.where': 'dispatched'}))
+    where = spec.program.constraints['cap'].where
+    assert where is not None and VariableDefined('p', ('period', 'generator')) in where.atoms
+
+
+@pytest.mark.parametrize(
+    ('patch', 'says'),
+    [
+        pytest.param({'masks': {'a': 'b', 'b': 'a'}}, 'circular mask reference: a -> b -> a', id='a-cycle'),
+        pytest.param({'masks': {'a': 'a'}}, 'circular mask reference: a -> a', id='a-mask-reading-itself'),
+        pytest.param({'masks': {'a': 'True'}}, 'folds to true, so the mask admits every row', id='always-true'),
+        pytest.param({'masks': {'a': 'NOT True'}}, 'folds to false, so the mask admits no row', id='always-false'),
+        pytest.param(
+            {'masks': {'a': 'c > 0'}, 'expressions.e': 'c * a'},
+            "'a' is a mask, which is true or false where it is read, and not a number",
+            id='a-mask-in-arithmetic',
+        ),
+        pytest.param(
+            {'masks': {'a': 'c > 0'}, 'variables.p.where': 'a == 1'},
+            "'a' is a mask, which is true or false where it is read, and not a number",
+            id='a-mask-compared',
+        ),
+        pytest.param(
+            {'given.masks.m': {'dims': ['g']}, 'expressions.e': 'c * m'},
+            "'m' is a mask, which is true or false where it is read, and not a number",
+            id='a-given-mask-in-arithmetic',
+        ),
+        pytest.param(
+            {'given.expressions.ge': {'dims': ['g']}, 'masks': {'a': 'ge > 0'}},
+            "where references the given expression 'ge'",
+            id='a-mask-reading-a-given-expression',
+        ),
+        pytest.param({'masks': {'c': 'flag'}}, "Mask 'c' collides with the parameter", id='a-name-taken'),
+        pytest.param({'masks': {'a': 'nope'}}, "Mask 'a': 'nope' not found", id='an-unknown-name'),
+        pytest.param(
+            {'masks': {'a': 'c > 0'}, 'variables.r.where': 'a'},
+            "outside the frame ['h']",
+            id='a-use-over-a-frame-the-predicate-leaves',
+        ),
+    ],
+)
+def test_what_a_mask_may_not_be_is_refused_at_load(patch, says):
+    with pytest.raises(LanguageError, match=None) as raised:
+        to_spec(varied(SMALL_MODEL, **patch))
+    assert says in str(raised.value), 'the refusal names the mask and what to write instead'
+
+
+def test_cases_split_by_a_mask_are_proved_apart_through_its_predicate():
+    """The overlap check evaluates a when on a grid of the data it reads, and a mask's data is its predicate's."""
+    case = {
+        'dims': ['g'],
+        'cases': {'on': {'when': 'a', 'expression': 1}, 'off': {'when': 'flag', 'expression': 2}},
+        'otherwise': 0,
+    }
+    with pytest.raises(LanguageError, match=r"cases 'on' and 'off' both claim the value where flag is true"):
+        to_spec(varied(SMALL_MODEL, **{'masks.a': 'flag', 'expressions.e': case}))
+    apart = varied(case, **{'cases.off.when': 'NOT a'})
+    assert to_spec(varied(SMALL_MODEL, **{'masks.a': 'flag', 'expressions.e': apart}))
+
+
+# ---------------------------------------------------------------------------
+# another file's mask
+# ---------------------------------------------------------------------------
+
+
+def test_a_fragment_reads_another_file_s_mask_as_boolean_data():
+    """#803's ramp read `active == 1` under `given: expressions:`, which a where may not read."""
+    program = to_spec(RAMPING).program
+    where = program.constraints['ramp_up'].where
+    assert where is not None and ParameterDefined('stands', ('period', 'generator')) in where.atoms, (
+        'alone, the reading is data the host provides'
+    )
+    assert sorted(program.given.masks) == ['stands']
+
+
+def test_check_notes_the_mask_a_fragment_reads():
+    """Every other given kind had a note saying who provides it, and a given mask had none."""
+    notes = {(note.kind, note.subject): note.text for note in advice(RAMPING)}
+    assert "mask 'stands' is read here and declared elsewhere" in notes[('given', 'stands')]
+
+
+@pytest.mark.parametrize(
+    'fragments',
+    [
+        pytest.param([CORE, RAMPING], id='the-definer-first'),
+        pytest.param([RAMPING, CORE], id='the-reader-first'),
+    ],
+)
+def test_merge_folds_the_reading_into_the_mask_another_fragment_defines(fragments):
+    program = merge(fragments).program
+    assert not program.given, 'the reading is spent once the definer is in the composition'
+    where = program.constraints['ramp_up'].where
+    assert where is not None and isinstance(where.conjuncts[0], NamedMask), 'the composed row reads the mask by name'
+
+
+@pytest.mark.parametrize(
+    ('reader', 'says'),
+    [
+        pytest.param(
+            varied(RAMPING, **{'given.masks.stands.dims': ['generator'], 'constraints.ramp_up.where': 'stands'}),
+            "reads the given mask 'stands'",
+            id='a-reader-that-states-less-than-the-frame',
+        ),
+        pytest.param(
+            varied(
+                RAMPING,
+                **{'given.masks': {}, 'given.parameters.stands': {'dims': FRAME, 'dtype': 'bool'}},
+            ),
+            "reads 'stands' as a given parameter, where '#1' introduces it under 'masks:'",
+            id='a-mask-read-as-a-parameter',
+        ),
+    ],
+)
+def test_a_reading_the_definer_does_not_answer_is_refused(reader, says):
+    with pytest.raises(LanguageError) as raised:
+        merge([CORE, reader])
+    assert says in str(raised.value)
+
+
+def test_a_reader_that_states_a_frame_wider_than_the_mask_s_is_refused():
+    """A reader stated a superset of the predicate's dims, and the merge took it.
+
+    A mask's frame is the dims its predicate reads, which no file chooses, so
+    a wider reading only defers the failure to the composed load.
+    """
+    definer = varied(CORE, **{'masks.stands': 'lifetime > 0'})
+    reader = varied(RAMPING, **{'constraints.ramp_up.where': 'stands'})
+    with pytest.raises(LanguageError) as raised:
+        merge([definer, reader])
+    assert "reads the given mask 'stands' as {'dims': ['period', 'generator']}" in str(raised.value), (
+        'the refusal names the frame the reader states'
+    )
+    assert "introduces it over ['generator']" in str(raised.value), "and the frame the definer's predicate reads"
+
+
+def test_two_fragments_that_define_one_mask_collide():
+    other = {'dimensions': DIMS, 'parameters': {'retired': {'dims': ['generator'], 'dtype': 'bool'}}}
+    with pytest.raises(LanguageError, match=r"fragments '#1' and '#2' both declare the mask 'stands'"):
+        merge([CORE, {**other, 'masks': {'stands': 'NOT retired'}}])
+
+
+def test_a_patch_rewrites_a_mask_s_predicate():
+    laid = override(CORE, [{'masks': {'stands': {'where': 'lifetime > 0'}}}])
+    assert laid.masks['stands'].where == 'lifetime > 0'
+    assert laid.masks['stands'].description == 'the unit stands in this period', 'a patch says only what it changes'
+
+
+# ---------------------------------------------------------------------------
+# typesetting
+# ---------------------------------------------------------------------------
+
+
+@pytest.mark.parametrize('fmt', sorted(FORMATS))
+def test_a_mask_prints_its_symbol_where_it_is_read_and_its_predicate_once(fmt):
+    printed = typeset(CORE, fmt)
+    defined = typeset_declaration(CORE, 'stands', fmt)
+    assert printed.count(FORMATS[fmt].operators['iff']) == 1, 'the predicate prints once, as the definition'
+    assert defined.split()[0].replace('\\_', '_').count('stands') == 1, 'the definition opens with the symbol'
+    assert FORMATS[fmt].operators['iff'] in defined, 'a predicate is defined with iff, not equated'
+    assert 'the unit stands in this period' in printed, 'the legend carries its words'
+
+
+@pytest.mark.parametrize('fmt', sorted(FORMATS))
+def test_a_given_mask_prints_in_the_legend_and_no_line_of_its_own(fmt):
+    assert 'a mask another file defines' in typeset(RAMPING, fmt)
+    with pytest.raises(LanguageError, match=r"'stands' is a given mask, and a given declaration prints no line"):
+        typeset_declaration(RAMPING, 'stands', fmt)
+
+
+def test_the_fixtures_are_never_mutated():
+    before = copy.deepcopy((CORE, RAMPING))
+    merge([CORE, RAMPING])
+    assert before == (CORE, RAMPING)
+
+
+def test_a_mask_with_no_declared_frame_takes_the_dims_its_predicate_reads():
+    spec = to_spec(varied(SMALL_MODEL, **{'masks.a': 'c > 0 AND flag'}))
+    assert spec.program.masks['a'].dims == ('g',)
+    assert spec.program.masks['a'].where == Mask(spec.program.masks['a'].where.root), 'the predicate is folded'
diff --git a/tests/test_validation.py b/tests/test_validation.py
index 0a46cd35..f7b17a6a 100644
--- a/tests/test_validation.py
+++ b/tests/test_validation.py
@@ -2369,6 +2369,15 @@ def test_an_infinite_bound_is_refused_with_the_null_that_opens_a_side(side, valu
         't',
         id='position',
     ),
+    pytest.param({'masks.first': 'position(t) == 0'}, 't', id='a-mask-predicate'),
+    pytest.param(
+        {
+            'masks.lit': 'on',
+            'constraints.c': {'dims': ['t'], 'where': 'shift(lit, along=t, offset=1)', 'expression': 'x <= 0'},
+        },
+        't',
+        id='a-shifted-mask',
+    ),
     pytest.param(
         {'piecewise.curve': {'over': 'bp', 'links': [['x', 'bp_x'], ['y', 'bp_y']]}},
         'bp',
diff --git a/tests/typesetting/golden/latex.out b/tests/typesetting/golden/latex.out
index 3815c78b..da63aa76 100644
--- a/tests/typesetting/golden/latex.out
+++ b/tests/typesetting/golden/latex.out
@@ -67,6 +67,12 @@
 \item[{$\mathrm{startup\_cost}$}] \texttt{startup\_cost} over $\mathcal{T} \times \mathcal{G}$ --- what starting a unit in this snapshot costs, which the horizon's edge changes
 \end{description}
 
+\paragraph{Masks}
+\begin{description}
+\item[{$\mathrm{dispatchable}$}] \texttt{dispatchable} over $\mathcal{G}$ --- a unit that dispatches and cannot be turned down
+\item[{$\mathrm{priced\_dispatch}$}] \texttt{priced\_dispatch} over $\mathcal{G}$
+\end{description}
+
 \noindent Upright is what the data supplies --- a parameter such as $\mathrm{p}^{\mathrm{max}}$, a coordinate map, a label --- and italic is what the solver chooses, such as $p$. An index is italic too, being what a quantifier chooses, and a set is script.
 
 \noindent $t \ominus k$ denotes cyclic translation: index $t-k$ taken modulo the size of the dimension (\texttt{roll}). Plain $t-k$ (\texttt{shift}) has no wraparound --- terms translated past the edge are simply absent.
@@ -136,6 +142,7 @@
 \text{run\_start} && \mathit{slack}_{t} & \le \mathrm{load}_{t,b} && \forall\, t \in \mathcal{T},\ b \in \mathcal{B} \,:\, \mathrm{load}_{t,b} \text{ is defined} \wedge \neg \left( \mathrm{load}_{t - 1,b} \text{ is defined} \right) \\
 \text{zoned} && \theta_{b} & \le \mathrm{budget} && \forall\, b \in \mathcal{B} \,:\, \mathrm{zone\_cap}_{\mathrm{zone\_of}(b)} \text{ is defined} \\
 \text{capped} && p_{t,g} & \le \mathrm{p}^{\mathrm{max}}_{g} && \forall\, t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{spend}^{\mathrm{cap}}_{g} > 0 \vee \neg \mathrm{is\_flexible}_{g} \\
+\text{masked} && p_{t,g} & \le \mathrm{p}^{\mathrm{max}}_{g} && \forall\, t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{priced\_dispatch}_{g} \wedge \mathrm{pos}(t) > 0 \\
 \text{fuel\_curve} && \left( p_{t,g},\ \mathit{fuel}_{t,g},\ \mathit{heat}_{t,g} \right) & \in \mathit{on}_{t,g} \cdot \mathrm{pwl}_{a \in \mathcal{A}}(\mathrm{bp\_x}_{g,a},\ \mathrm{bp\_y}_{g,a},\ \mathrm{bp\_heat}_{g,a}) && \forall\, t \in \mathcal{T},\ g \in \mathcal{G} \\
 \text{cost\_curve} && \mathit{op\_cost}_{t,g} & \ge \begin{cases} \mathit{warm}_{t,g} & \text{if } \mathrm{is\_flexible}_{g} \\ 1 & \text{otherwise} \end{cases} \cdot \mathrm{pwl}_{a \in \mathcal{A} \,:\, \mathrm{bp\_run}_{g,a}}(\mathrm{bp\_x}_{g,a},\ \mathrm{bp\_y}_{g,a})(p_{t,g}) && \forall\, t \in \mathcal{T},\ g \in \mathcal{G} \\
 \text{hull\_curve} && \left( p_{t,g},\ \mathit{fuel}_{t,g} \right) & \in \mathrm{conv}_{a \in \mathcal{A}}(\mathrm{bp\_x}_{g,a},\ \mathrm{bp\_heat}_{g,a}) && \forall\, t \in \mathcal{T},\ g \in \mathcal{G} \\
@@ -154,6 +161,12 @@
 \text{startup\_cost} && \mathrm{startup\_cost}_{t,g} & = \begin{cases} \mathrm{cost}_{g} & \text{if } \mathrm{pos}(t) = 0 \\ \mathrm{cost}_{g} \cdot 2 & \text{if } \mathrm{pos}(t) > 0 \wedge \mathrm{season\_of}(t) = \text{'}\mathrm{winter}\text{'} \\ 0 & \text{otherwise} \end{cases} && \forall\, t \in \mathcal{T},\ g \in \mathcal{G}
 \end{align}
 
+\paragraph{Masks}
+\begin{align}
+\text{dispatchable} && \mathrm{dispatchable}_{g} & \iff \mathrm{p}^{\mathrm{max}}_{g} > 0 \wedge \neg \mathrm{is\_flexible}_{g} && \forall\, g \in \mathcal{G} \\
+\text{priced\_dispatch} && \mathrm{priced\_dispatch}_{g} & \iff \mathrm{dispatchable}_{g} \wedge \mathrm{spend}^{\mathrm{cap}}_{g} > 0 && \forall\, g \in \mathcal{G}
+\end{align}
+
 \paragraph{Variable domains}
 \begin{align}
 \text{p} && \mathrm{p}^{\mathrm{min}}_{g} \le p_{t,g} & \le \mathrm{p}^{\mathrm{max}}_{g} && \forall\, t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{p}^{\mathrm{max}}_{g} > 0 \wedge \neg \mathrm{is\_flexible}_{g} \vee \mathrm{p}^{\mathrm{min}}_{g} > 0 \\
diff --git a/tests/typesetting/golden/markdown.out b/tests/typesetting/golden/markdown.out
index 879bbe67..1be024bb 100644
--- a/tests/typesetting/golden/markdown.out
+++ b/tests/typesetting/golden/markdown.out
@@ -66,6 +66,13 @@ every character a notation escapes, set as text: link\_to, 100% & \#1 costs \$5
 | $`\mathit{marginal\_price}`$ | `marginal_price` over $`\mathcal{T} \times \mathcal{B}`$ |
 | $`\mathrm{startup\_cost}`$ | `startup_cost` over $`\mathcal{T} \times \mathcal{G}`$ — what starting a unit in this snapshot costs, which the horizon's edge changes |
 
+#### Masks
+
+| Symbol | Meaning |
+|---|---|
+| $`\mathrm{dispatchable}`$ | `dispatchable` over $`\mathcal{G}`$ — a unit that dispatches and cannot be turned down |
+| $`\mathrm{priced\_dispatch}`$ | `priced_dispatch` over $`\mathcal{G}`$ |
+
 Upright is what the data supplies — a parameter such as $`\mathrm{p}^{\mathrm{max}}`$, a coordinate map, a label — and italic is what the solver chooses, such as $`p`$. An index is italic too, being what a quantifier chooses, and a set is script.
 
 $`t \ominus k`$ denotes cyclic translation: index $`t-k`$ taken modulo the size of the dimension (`roll`). Plain $`t-k`$ (`shift`) has no wraparound — terms translated past the edge are simply absent.
@@ -376,6 +383,12 @@ p_{t,g} \le \mathrm{p}^{\mathrm{max}}_{g} \qquad \forall\, t \in \mathcal{T},\ g
 p_{t,g} \le \mathrm{p}^{\mathrm{max}}_{g} \qquad \forall\, t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{spend}^{\mathrm{cap}}_{g} > 0 \vee \neg \mathrm{is\_flexible}_{g}
 ```
 
+**`masked`**
+
+```math
+p_{t,g} \le \mathrm{p}^{\mathrm{max}}_{g} \qquad \forall\, t \in \mathcal{T},\ g \in \mathcal{G} \,:\, \mathrm{priced\_dispatch}_{g} \wedge \mathrm{pos}(t) > 0
+```
+
 **`fuel_curve`**
 
 ```math
@@ -450,6 +463,20 @@ p_{t,g} \le \mathrm{p}^{\mathrm{max}}_{g} \qquad \forall\, t \in \mathcal{T},\ g
 \mathrm{startup\_cost}_{t,g} = \begin{cases} \mathrm{cost}_{g} & \text{if } \mathrm{pos}(t) = 0 \\ \mathrm{cost}_{g} \cdot 2 & \text{if } \mathrm{pos}(t) > 0 \wedge \mathrm{season\_of}(t) = \text{'}\mathrm{winter}\text{'} \\ 0 & \text{otherwise} \end{cases} \qquad \forall\, t \in \mathcal{T},\ g \in \mathcal{G}
 ```
 
+#### Masks
+
+**`dispatchable`**
+
+```math
+\mathrm{dispatchable}_{g} \iff \mathrm{p}^{\mathrm{max}}_{g} > 0 \wedge \neg \mathrm{is\_flexible}_{g} \qquad \forall\, g \in \mathcal{G}
+```
+
+**`priced_dispatch`**
+
+```math
+\mathrm{priced\_dispatch}_{g} \iff \mathrm{dispatchable}_{g} \wedge \mathrm{spend}^{\mathrm{cap}}_{g} > 0 \qquad \forall\, g \in \mathcal{G}
+```
+
 #### Variable domains
 
 **`p`**
diff --git a/tests/typesetting/golden/model.yaml b/tests/typesetting/golden/model.yaml
index 259a4b74..81cef789 100644
--- a/tests/typesetting/golden/model.yaml
+++ b/tests/typesetting/golden/model.yaml
@@ -159,6 +159,12 @@ expressions:
       winter: { when: "position(snapshot) > 0 and season_of == 'winter'", expression: cost * 2 }
     otherwise: 0
 
+masks:
+  dispatchable: # a named predicate with its words: a use prints the symbol over the dims its predicate reads, the predicate prints once
+    where: "p_max > 0 AND NOT is_flexible"
+    description: a unit that dispatches and cannot be turned down
+  priced_dispatch: "dispatchable AND spend_cap > 0" # the one-line form, reading another mask and a data-only entry
+
 constraints:
   budgeted: # names the plain expression: its symbol prints here, its definition once below
     dims: [snapshot]
@@ -327,6 +333,10 @@ constraints:
     dims: [snapshot, generator]
     where: "spend_cap > 0 OR NOT is_flexible"
     expression: p <= p_max
+  masked: # a mask as the where, beside a condition of the constraint's own
+    dims: [snapshot, generator]
+    where: "priced_dispatch AND position(snapshot) > 0"
+    expression: p <= p_max
 
 assumptions: # what the data has to satisfy for the answer to mean anything
   bounds_do_not_cross: "p_min <= p_max" # two parameters, which is arithmetic like any other
diff --git a/tests/typesetting/golden/typst.out b/tests/typesetting/golden/typst.out
index 8f245ca9..261e376e 100644
--- a/tests/typesetting/golden/typst.out
+++ b/tests/typesetting/golden/typst.out
@@ -55,6 +55,10 @@ every character a notation escapes, set as text: link\_to, 100% & \#1 costs \$5
 / $italic("marginal_price")$: `marginal_price` over $cal(T) times cal(B)$
 / $upright("startup_cost")$: `startup_cost` over $cal(T) times cal(G)$ --- what starting a unit in this snapshot costs, which the horizon's edge changes
 
+== Masks
+/ $upright("dispatchable")$: `dispatchable` over $cal(G)$ --- a unit that dispatches and cannot be turned down
+/ $upright("priced_dispatch")$: `priced_dispatch` over $cal(G)$
+
 Upright is what the data supplies --- a parameter such as $upright("p")^(upright("max"))$, a coordinate map, a label --- and italic is what the solver chooses, such as $p$. An index is italic too, being what a quantifier chooses, and a set is script.
 
 $t minus.o k$ denotes cyclic translation: index $t-k$ taken modulo the size of the dimension (`roll`). Plain $t-k$ (`shift`) has no wraparound --- terms translated past the edge are simply absent.
@@ -123,6 +127,7 @@ $ upright("budgeted") & italic("spend")_(t) & <= upright("budget") & forall t in
   upright("run_start") & italic("slack")_(t) & <= upright("load")_(t,b) & forall t in cal(T), b in cal(B) colon upright("load")_(t,b) upright(" is defined") and not (upright("load")_(t - 1,b) upright(" is defined")) \
   upright("zoned") & theta_(b) & <= upright("budget") & forall b in cal(B) colon upright("zone_cap")_(upright("zone_of")(b)) upright(" is defined") \
   upright("capped") & p_(t,g) & <= upright("p")^(upright("max"))_(g) & forall t in cal(T), g in cal(G) colon upright("spend")^(upright("cap"))_(g) > 0 or not upright("is_flexible")_(g) \
+  upright("masked") & p_(t,g) & <= upright("p")^(upright("max"))_(g) & forall t in cal(T), g in cal(G) colon upright("priced_dispatch")_(g) and upright("pos")(t) > 0 \
   upright("fuel_curve") & (p_(t,g), italic("fuel")_(t,g), italic("heat")_(t,g)) & in italic("on")_(t,g) dot upright("pwl")_(a in cal(A))(upright("bp_x")_(g,a), upright("bp_y")_(g,a), upright("bp_heat")_(g,a)) & forall t in cal(T), g in cal(G) \
   upright("cost_curve") & italic("op_cost")_(t,g) & >= cases(italic("warm")_(t,g) & upright("if ") upright("is_flexible")_(g), 1 & upright("otherwise")) dot upright("pwl")_(a in cal(A) colon upright("bp_run")_(g,a))(upright("bp_x")_(g,a), upright("bp_y")_(g,a))(p_(t,g)) & forall t in cal(T), g in cal(G) \
   upright("hull_curve") & (p_(t,g), italic("fuel")_(t,g)) & in upright("conv")_(a in cal(A))(upright("bp_x")_(g,a), upright("bp_heat")_(g,a)) & forall t in cal(T), g in cal(G) \
@@ -139,6 +144,11 @@ $ upright("spend_cap") & upright("spend")^(upright("cap"))_(g) & = upright("cost
   upright("marginal_price") & italic("marginal_price")_(t,b) & = lambda_(upright("balance"),t,b) & forall t in cal(T), b in cal(B) \
   upright("startup_cost") & upright("startup_cost")_(t,g) & = cases(upright("cost")_(g) & upright("if ") upright("pos")(t) = 0, upright("cost")_(g) dot 2 & upright("if ") upright("pos")(t) > 0 and upright("season_of")(t) = upright("'winter'"), 0 & upright("otherwise")) & forall t in cal(T), g in cal(G) $
 
+== Masks
+#set math.equation(numbering: "(1)")
+$ upright("dispatchable") & upright("dispatchable")_(g) & arrow.l.r.double.long upright("p")^(upright("max"))_(g) > 0 and not upright("is_flexible")_(g) & forall g in cal(G) \
+  upright("priced_dispatch") & upright("priced_dispatch")_(g) & arrow.l.r.double.long upright("dispatchable")_(g) and upright("spend")^(upright("cap"))_(g) > 0 & forall g in cal(G) $
+
 == Variable domains
 #set math.equation(numbering: "(1)")
 $ upright("p") & upright("p")^(upright("min"))_(g) <= p_(t,g) & <= upright("p")^(upright("max"))_(g) & forall t in cal(T), g in cal(G) colon upright("p")^(upright("max"))_(g) > 0 and not upright("is_flexible")_(g) or upright("p")^(upright("min"))_(g) > 0 \
diff --git a/tests/typesetting/test_declaration.py b/tests/typesetting/test_declaration.py
index 005eecce..3213c376 100644
--- a/tests/typesetting/test_declaration.py
+++ b/tests/typesetting/test_declaration.py
@@ -161,7 +161,7 @@ def test_a_substituted_term_that_opens_with_a_minus_prints_as_a_subtraction():
         pytest.param(
             PLAIN,
             'spent',
-            r"'spent' is not a named expression, constraint, assumption, curve or variable.*spend",
+            r"'spent' is not a named expression, mask, constraint, assumption, curve or variable.*spend",
             id='a-near-miss',
         ),
         pytest.param(PLAIN, 'objective', r"'objective' is not a named expression", id='the-objective-has-no-name'),
diff --git a/tools/gallery.py b/tools/gallery.py
index 538eca3a..131755f6 100644
--- a/tools/gallery.py
+++ b/tools/gallery.py
@@ -113,6 +113,8 @@ def symbols_for(model: Spec, table_path: Path = LIBRARY_SYMBOLS) -> dict[str, An
         *given.variables,
         *given.expressions,
         *given.constraints,
+        *model.masks,
+        *given.masks,
     }
     return {
         'notation': table['notation'],
diff --git a/tools/notation.py b/tools/notation.py
index a4411206..2d15d25e 100644
--- a/tools/notation.py
+++ b/tools/notation.py
@@ -51,7 +51,7 @@
 #: and ``parameters`` are absent on purpose: they declare no equation, and what
 #: they print is the legend, which the page shows once rather than a row at a
 #: time.
-BLOCKS = ('objective', 'constraints', 'expressions', 'variables', 'piecewise', 'sos', 'assumptions')
+BLOCKS = ('objective', 'constraints', 'expressions', 'masks', 'variables', 'piecewise', 'sos', 'assumptions')
 
 #: The page's sections in the order of the language reference, and in each the
 #: fixture's declarations under the construct they show. The declaration name
@@ -114,6 +114,11 @@
         'lcoe': 'Reported expression',
         'marginal_price': 'Dual of a constraint',
     },
+    'Named masks': {
+        'dispatchable': 'Named mask',
+        'priced_dispatch': 'Mask that reads a mask',
+        'masked': 'Mask in a condition',
+    },
     'Shifts': {
         'ramp': 'Cyclic and acyclic shift',
         'edges': 'Filled and forward shifts',
diff --git a/tools/pypsa_split.py b/tools/pypsa_split.py
index 17639c0f..e6b5b58f 100644
--- a/tools/pypsa_split.py
+++ b/tools/pypsa_split.py
@@ -18,7 +18,9 @@
 with `adds_to:`, and the fragment reads that hub under `given:`. One fragment
 reads each hub without adding to it, with its description, so the terms always
 have a reader, and a new component is one new fragment. The reader of
-`total_cost` also sets the objective.
+`total_cost` also sets the objective. A mask goes to the topic its name
+names, as any declaration does, and a fragment that reads another topic's
+mask reads it under `given: masks:`.
 
 `merge` then writes each hub as the file does, so `check` is one comparison:
 the merged fragments and the one file have one canonical form.
@@ -46,7 +48,7 @@
     from collections.abc import Mapping
 
 SOURCE = Path('examples/pypsa.yaml')
-SECTIONS = ('dimensions', 'relations', 'parameters', 'variables', 'expressions', 'constraints', 'assumptions')
+SECTIONS = ('dimensions', 'relations', 'parameters', 'variables', 'expressions', 'masks', 'constraints', 'assumptions')
 FRAME = ('dimensions', 'relations')
 IDENT = re.compile(r'[A-Za-z_][A-Za-z0-9_]*')
 HEADER = '# SPDX-FileCopyrightText: mathspec Contributors\n#\n# SPDX-License-Identifier: MIT\n'
@@ -221,8 +223,12 @@ def keys(self) -> list[Key]:
         return list(self.blocks)
 
     def frames(self) -> dict[str, tuple[str, ...]]:
-        """The frame of every named expression, read off the one file."""
-        return {name: e.dims for name, e in to_spec(self.data).program.expressions.items()}
+        """The frame of every named expression and mask, read off the one file."""
+        program = to_spec(self.data).program
+        return {
+            **{name: e.dims for name, e in program.expressions.items()},
+            **{name: m.dims for name, m in program.masks.items()},
+        }
 
     def home(self, name: str) -> str:
         """The fragment that reads the hub *name* without adding to it, and carries its description."""
@@ -255,7 +261,7 @@ def fragments(model: Model) -> dict[str, str]:
         given = {model.key(n) for n in read if model.key(n)[0] not in FRAME and model.key(n) not in mine}
         stated = {
             **{n: model.data[s][n]['dims'] for s, n in given if s in ('parameters', 'variables')},
-            **{n: list(frames[n]) for s, n in given if s == 'expressions'},
+            **{n: list(frames[n]) for s, n in given if s in ('expressions', 'masks')},
         }
         frame_reads = read | set().union(*(model.names_in(dims) for dims in stated.values()))
         frame = {model.key(n) for n in frame_reads if model.key(n)[0] in FRAME}
@@ -319,7 +325,7 @@ def _fragment(
 
 #: The kinds a fragment reads under `given:`, and the fields of the source
 #: declaration each restates beside the frame.
-GIVEN_KINDS = {'parameters': ('dtype',), 'variables': ('domain',), 'expressions': ()}
+GIVEN_KINDS = {'parameters': ('dtype',), 'variables': ('domain',), 'expressions': (), 'masks': ()}
 
 
 def _term_block(block: str, hub: str) -> str: