From 637286ce2e767f9dc47dcb3e087d7ac254393bc1 Mon Sep 17 00:00:00 2001
From: Francis Charette Migneault <francis.charette.migneault@gmail.com>
Date: Fri, 11 Sep 2026 17:29:31 -0400
Subject: [PATCH] Add hasFormat relation for alternate-format sibling Building
 Blocks

hasFormat represents dcterms:hasFormat/isFormatOf semantics: two Building
Blocks that are substantially the same content in another format (e.g. a
JSON vs an XML serialization of the same model), as opposed to isProfileOf's
specialization/inheritance semantics.

- bblock.schema.yaml: add hasFormat (array of bblock references), symmetric,
  intended to be declared on every sibling that should be linked
- models.py: normalize bblocks:// prefixes on hasFormat like dependsOn/isProfileOf
- register-context.yaml: map hasFormat to dct:hasFormat, and add the
  previously-missing seeAlso -> rdfs:seeAlso mapping (the property name itself
  had no JSON-LD context term, unlike its raw rdfs:seeAlso IRI counterpart)
---
 ogc/bblocks/models.py                  |  5 +++++
 ogc/bblocks/register-context.yaml      |  6 ++++++
 ogc/bblocks/schemas/bblock.schema.yaml | 10 ++++++++++
 3 files changed, 21 insertions(+)

diff --git a/ogc/bblocks/models.py b/ogc/bblocks/models.py
index 7862af1..947acd6 100644
--- a/ogc/bblocks/models.py
+++ b/ogc/bblocks/models.py
@@ -233,6 +233,9 @@ def __init__(self, identifier: str, metadata_file: Path,
         if 'dependsOn' in self.metadata:
             self.metadata['dependsOn'] = [strip_bblocks_uri(d) for d in self.metadata['dependsOn']]
 
+        if 'hasFormat' in self.metadata:
+            self.metadata['hasFormat'] = [strip_bblocks_uri(d) for d in self.metadata['hasFormat']]
+
         ep = self.metadata.get('extensionPoints')
         if ep:
             if 'baseBuildingBlock' in ep:
@@ -692,6 +695,8 @@ def load(self, metadata_url: str) -> tuple[list[str], str]:
             bblock['register'] = self
             if 'dependsOn' in bblock:
                 bblock['dependsOn'] = [strip_bblocks_uri(d) for d in bblock['dependsOn']]
+            if 'hasFormat' in bblock:
+                bblock['hasFormat'] = [strip_bblocks_uri(d) for d in bblock['hasFormat']]
             if 'isProfileOf' in bblock:
                 v = bblock['isProfileOf']
                 bblock['isProfileOf'] = ([strip_bblocks_uri(i) for i in v]
diff --git a/ogc/bblocks/register-context.yaml b/ogc/bblocks/register-context.yaml
index 9ed33e0..18698c5 100644
--- a/ogc/bblocks/register-context.yaml
+++ b/ogc/bblocks/register-context.yaml
@@ -123,6 +123,12 @@ context:
     isProfileOf:
       '@id': prof:isProfileOf
       '@type': '@id'
+    hasFormat:
+      '@id': dct:hasFormat
+      '@type': '@id'
+    seeAlso:
+      '@id': rdfs:seeAlso
+      '@type': '@id'
     tags: dcat:keyword
     shaclShapes:
       '@id': prof:hasResource
diff --git a/ogc/bblocks/schemas/bblock.schema.yaml b/ogc/bblocks/schemas/bblock.schema.yaml
index 9a01974..c763b62 100644
--- a/ogc/bblocks/schemas/bblock.schema.yaml
+++ b/ogc/bblocks/schemas/bblock.schema.yaml
@@ -195,6 +195,16 @@ properties:
     type: array
     items:
       type: string
+  hasFormat:
+    description: >-
+      Identifiers of other Building Blocks that represent the same content as this one, but in
+      an alternate format (equivalent to Dublin Core's dcterms:hasFormat/isFormatOf). Unlike
+      isProfileOf, this does not imply one is a specialization of the other - they are siblings.
+      Symmetric: list the relation on every sibling that should be linked, since it is not
+      inferred automatically from the other side.
+    type: array
+    items:
+      type: string
   requirementClasses:
     description: URI(s) of requirement classes that can be used to validate this Building Block
     type: array