diff --git a/Common.json b/Common.json
index fb55398..1354e84 100644
--- a/Common.json
+++ b/Common.json
@@ -1,53 +1,103 @@
 {
-  "$schema": "http://json-schema.org/draft-04/schema#",
-  "id": "http://raw.githubusercontent.com/peterataylor/om-json/master/Common.json",
-  "title": "Common",
-  "description": "A collection of commonly used types. Should maybe come from somehwere else, one day.",
-  "definitions": {
-    "count": {
-      "title": "count",
-      "type": "integer"
-    },
-    "measure": {
-      "title": "measure",
-      "description": "scaled number - uom is optional, to support the case where a common uom is used in a collection",
-      "type": "object",
-      "properties": {
-        "value": { "type": "number" },
-        "uom": { "type": "string" }
-      },
-      "required": [ "value" ],
-      "additionalProperties": false
-    },
-    "text": {
-      "title": "text",
-      "type": "string"
-    },
-    "truth": {
-      "title": "truth",
-      "type": "boolean"
-    },
-    "vocabTerm": {
-      "title": "vocabTerm",
-      "description": "term with optional vocabulary source",
-      "type": "object",
-      "properties": {
-        "term": { "type": "string" },
-        "vocabulary": { "type": "string", "format": "uri" }
-      },
-      "required": [ "term" ],
-      "additionalProperties": false
-    },
-    "link": {
-      "title": "link",
-      "type": "object",
-      "properties": {
-        "href": { "type": "string", "format": "uri" },
-        "rel": { "type": "string", "format": "uri" },
-        "title": { "type": "string" }
-      },
-      "required": [ "href" ],
-      "additionalProperties":false
-    }
-  }
+	"$schema": "http://json-schema.org/draft-04/schema#",
+	"id": "http://raw.githubusercontent.com/peterataylor/om-json/master/Common.json",
+	"title": "Common",
+	"description": "A collection of commonly used types. Should maybe come from somehwere else, one day.",
+	"definitions": {
+		"@context": {
+			"oneOf": [{
+				"title": "@context",
+				"description": "A context header for JSON-LD applications - using string here to allow for a remote context",
+				"type": "string"},
+				{"title": "@context",
+				"description": "A context header for JSON-LD applications - using array here to allow for a local context",
+				"type": "array"}
+			]
+		},
+		"count": {
+			"title": "count",
+			"type": "integer"
+		},
+		"measure": {
+			"title": "measure",
+			"description": "scaled number - uom is optional, to support the case where a common uom is used in a collection",
+			"type": "object",
+			"properties": {
+				"value": {
+					"type": "number"
+				},
+				"uom": {
+					"oneOf": [
+					{"type": "string"},
+					{ "$ref": "http://raw.githubusercontent.com/peterataylor/om-json/master/Common.json#/definitions/vocabTerm" }]
+					}
+				},
+			"required": [
+				"value"
+			],
+			"additionalProperties": false
+		},
+		"text": {
+			"title": "text",
+			"type": "string"
+		},
+		"truth": {
+			"title": "truth",
+			"type": "boolean"
+		},
+		"vocabTerm": {
+			"title": "vocabTerm",
+			"description": "term with optional vocabulary source",
+			"type": "object",
+			"properties": {
+				"term": {
+					"type": "string"
+				},
+				"vocabulary": {
+					"type": "string",
+					"format": "uri"
+				}
+			},
+			"required": [
+				"term"
+			],
+			"additionalProperties": false
+		},
+		"link": {
+			"title": "link",
+			"type": "object",
+			"properties": {
+				"href": {
+					"type": "string",
+					"format": "uri"
+				},
+				"rel": {
+					"type": "string",
+					"format": "uri"
+				},
+				"title": {
+					"type": "string"
+				}
+			},
+			"required": [
+				"href"
+			],
+			"additionalProperties": false
+		},
+		"doi": {
+			"title": "doi",
+			"description": "A Digital Object Identifer to define a resource",
+			"type": "object",
+			"properties": {
+				"doi": {
+					"type": "string",
+					"format": "uri"
+				}
+			},
+			"required": [
+				"doi"
+			],
+			"additionalProperties": false
+		}
+	}
 }
diff --git a/Geometry.json b/Geometry.json
index df3d3a4..df557ad 100644
--- a/Geometry.json
+++ b/Geometry.json
@@ -113,6 +113,7 @@
         }
     },
     "properties": {
+		"@context" : { "$ref": "http://raw.githubusercontent.com/peterataylor/om-json/master/Common.json#/definitions/@context" },
         "geometry": { "$ref": "#/definitions/geometryObject"}        
     },
     "required": [ "geometry" ]
diff --git a/Measurement.json b/Measurement.json
index eba1e97..c1326f8 100644
--- a/Measurement.json
+++ b/Measurement.json
@@ -8,6 +8,7 @@
     { "$ref": "http://raw.githubusercontent.com/peterataylor/om-json/master/Observation.json" }
   ],
   "properties": {
+    "@context" : { "$ref": "http://raw.githubusercontent.com/peterataylor/om-json/master/Common.json#/definitions/@context" },
     "id": { },
     "type": { "enum": [ "Measurement" ] } ,
     "phenomenonTime": { },
diff --git a/MonitoringFeature.json b/MonitoringFeature.json
index 0399397..df11766 100644
--- a/MonitoringFeature.json
+++ b/MonitoringFeature.json
@@ -24,6 +24,12 @@
     }
   },
   "properties": {
+ 	"@context" : { "$ref": "http://raw.githubusercontent.com/peterataylor/om-json/master/Common.json#/definitions/@context" },
+  	"id": {
+      "title": "id",
+      "description": "A unique identifier for the observation",
+      "type": "string"
+    },
     "relatedParty": {
       "title": "relatedParty",
       "description": "The details of a party related to this MonitoringFeature.  Multiple related parties may be described using the role code list (from ISO 19115). The most common relationships are likely to be: owner, originator, pointOfContact, principalInvestigator and distributor.",
@@ -32,7 +38,7 @@
     "representativePoint": {
       "title": "representativePoint",
       "description": "A point location that is representative of the monitoring feature's location. Typically this is used when the shape of the monitoring feature is an area or other non-point geometry. It may also be used to provide an approximate point location in sensitive observation scenarios.",
-      "$ref": "http://raw.githubusercontent.com/peterataylor/om-json/master/Common.json#/definitions/geometryObject"
+      "$ref": "http://raw.githubusercontent.com/peterataylor/om-json/master/Geometry.json#/definitions/geometryObject"
     },
     "monitoringType": {
       "title": "monitoringType",
diff --git a/Observation.json b/Observation.json
index ae9403b..bd13b1f 100644
--- a/Observation.json
+++ b/Observation.json
@@ -5,6 +5,7 @@
   "description": "An observation is an act associated with a discrete time instant or period through which a number, term or other symbol is assigned to a phenomenon. It involves application of a specified procedure, such as a sensor, instrument, algorithm or process chain. The procedure may be applied in-situ, remotely, or ex-situ with respect to the sampling location. The result of an observation is an estimate of the value of a property of some feature.",
   "type": "object",
   "properties": {
+  	"@context" : { "$ref": "http://raw.githubusercontent.com/peterataylor/om-json/master/Common.json#/definitions/@context" },
     "id": {
       "title": "id",
       "description": "A unique identifier for the observation",
@@ -30,17 +31,27 @@
     "observedProperty": {
       "title": "observedProperty",
       "description": "property whose value is the result of the observation",
-      "$ref": "http://raw.githubusercontent.com/peterataylor/om-json/master/Common.json#/definitions/link"
+	  "oneOf": [
+		{"$ref": "http://raw.githubusercontent.com/peterataylor/om-json/master/Common.json#/definitions/link"},
+		{"$ref": "http://raw.githubusercontent.com/peterataylor/om-json/master/Common.json#/definitions/vocabTerm"}
+	  ]
     },
     "procedure": {
       "title": "procedure",
       "description": "procedure used in making observation. Typically a sensor or sensor-system, algorithm, computational procedure.",
-      "$ref": "http://raw.githubusercontent.com/peterataylor/om-json/master/Common.json#/definitions/link"
+	  "oneOf": [
+		{ "$ref": "http://raw.githubusercontent.com/peterataylor/om-json/master/Common.json#/definitions/link" },
+		{ "$ref": "http://raw.githubusercontent.com/peterataylor/om-json/master/Common.json#/definitions/vocabTerm" },
+		{ "$ref": "http://raw.githubusercontent.com/adamml/om-json/master/ocean-acidification/Protocol.json" } 
+	  ]
     },
     "featureOfInterest": {
       "title": "featureOfInterest",
       "description": "subject of the observation, whose type may carry the observed property",
-      "$ref": "http://raw.githubusercontent.com/peterataylor/om-json/master/Common.json#/definitions/link"
+	  "oneOf": [
+		{"$ref": "http://raw.githubusercontent.com/peterataylor/om-json/master/Common.json#/definitions/link"},
+		{ "$ref": "http://raw.githubusercontent.com/peterataylor/om-json/master/Common.json#/definitions/vocabTerm" }
+	  ]
     },
     "samplingStrategy": {
       "title": "samplingStrategy",
@@ -67,7 +78,8 @@
         { "$ref": "http://raw.githubusercontent.com/peterataylor/om-json/master/Common.json#/definitions/text"            },
         { "$ref": "http://raw.githubusercontent.com/peterataylor/om-json/master/Temporal.json#/definitions/temporalObject" },
         { "$ref": "http://raw.githubusercontent.com/peterataylor/om-json/master/Geometry.json#/definitions/geometryObject" },
-        { "$ref": "http://raw.githubusercontent.com/peterataylor/om-json/master/TimeseriesTVP.json#/definitions/TimeseriesTVP" }
+        { "$ref": "http://raw.githubusercontent.com/peterataylor/om-json/master/TimeseriesTVP.json#/definitions/TVPairMeasure" },
+        { "$ref": "http://raw.githubusercontent.com/peterataylor/om-json/master/TimeseriesTVP.json#/definitions/TVPairCategory" }
       ]
     }
   },
diff --git a/ObservationCollection.json b/ObservationCollection.json
index 78d3d18..29c7fa6 100644
--- a/ObservationCollection.json
+++ b/ObservationCollection.json
@@ -9,6 +9,7 @@
     "member"
   ],
   "properties": {
+  	"@context" : { "$ref": "http://raw.githubusercontent.com/peterataylor/om-json/master/Common.json#/definitions/@context" },
     "id": {
       "title": "id",
       "description": "A unique identifier for the observation collection",
diff --git a/Sampling.json b/Sampling.json
index 42a1b43..9a5ebba 100644
--- a/Sampling.json
+++ b/Sampling.json
@@ -5,6 +5,7 @@
   "description": "Feature on which observations may be made, which is intended to be representative of a different (usually larger) feature that is not fully accessible for some reason.",
   "type": "object",
   "properties": {
+  	"@context" : { "$ref": "http://raw.githubusercontent.com/peterataylor/om-json/master/Common.json#/definitions/@context" },
     "id": {
       "title": "id",
       "description": "A unique identifier for the sampling feature",
diff --git a/SamplingCollection.json b/SamplingCollection.json
index a895093..dcdf7fc 100644
--- a/SamplingCollection.json
+++ b/SamplingCollection.json
@@ -5,6 +5,7 @@
   "description": "Collection of features on which observations may be made.",
   "type": "object",
   "properties": {
+  	"@context" : { "$ref": "http://raw.githubusercontent.com/peterataylor/om-json/master/Common.json#/definitions/@context" },
     "id": {
       "title": "id",
       "description": "A unique identifier for the sampling feature collection",
@@ -13,7 +14,8 @@
     "type": {
       "title": "type",
       "description": "Identifies the type of object",
-      "type": "enum"
+      "type": "string",
+      "enum": ["Specimen","Sampling","SpatialSampling"]
     },
     "sampledFeature": {
       "title": "sampledFeature",
@@ -28,7 +30,7 @@
       "description": "Member of this sampling feature collection",
       "type": "array",
       "items": {
-        "anyOf": [
+        "oneOf": [
           { "$ref": "http://raw.githubusercontent.com/peterataylor/om-json/master/Common.json#/definitions/link" },
           { "$ref": "http://raw.githubusercontent.com/peterataylor/om-json/master/Sampling.json" },
           { "$ref": "http://raw.githubusercontent.com/peterataylor/om-json/master/Specimen.json" },
diff --git a/SpatialSampling.json b/SpatialSampling.json
index 9dd275a..a1af24d 100644
--- a/SpatialSampling.json
+++ b/SpatialSampling.json
@@ -1,6 +1,6 @@
 {
   "$schema": "http://json-schema.org/draft-04/schema#",
-  "id": "http://raw.githubusercontent.com/peterataylor/om-json/master/SpatialSampling.json",
+  "id": "http://raw.githubusercontent.com/adamml/om-json/master/SpatialSampling.json",
   "title": "Spatial Sampling Feature",
   "description": "  ## EXTENDS SAMPLING FEATURE ##  Sampling feature whose defining characteristic is that it samples the intended feature by geometric subsetting. ",
   "type": "object",
@@ -24,6 +24,7 @@
     }
   ],
   "properties": {
+  	"@context" : { "$ref": "http://raw.githubusercontent.com/peterataylor/om-json/master/Common.json#/definitions/@context" },
     "id": {},
     "type": { "enum": [ "SamplingPoint" , "SamplingCurve" , "SamplingSurface" , "SamplingSolid" ] },
     "sampledFeature": {},
diff --git a/Temporal.json b/Temporal.json
index abe73b4..0cde42a 100644
--- a/Temporal.json
+++ b/Temporal.json
@@ -71,6 +71,7 @@
     }
   },
   "properties": {
+		"@context" : { "$ref": "http://raw.githubusercontent.com/peterataylor/om-json/master/Common.json#/definitions/@context" },
         "time": { "$ref": "#/definitions/temporalObject" }        
   },
   "required": [ "time" ]
diff --git a/TimeseriesMetadata.json b/TimeseriesMetadata.json
index ddaf953..d1d06c3 100644
--- a/TimeseriesMetadata.json
+++ b/TimeseriesMetadata.json
@@ -9,6 +9,7 @@
       "description":"Metadata for the whole timeseries",
       "type":"object",
       "properties" : {
+	  	"@context" : { "$ref": "http://raw.githubusercontent.com/peterataylor/om-json/master/Common.json#/definitions/@context" },
         "temporalExtent": {
           "title":"temporalExtent",
           "type":"object",
@@ -41,7 +42,7 @@
           "title":"commentBlocks",
           "type":"array",
           "items" : { 
-            "$ref":"#/definitions/commentBlock"
+            "$ref":"#/definitions/TimeseriesMetadata/properties/commentBlock"
           }
         },
         "intendedObservationSpacing": {
diff --git a/TimeseriesTVP.json b/TimeseriesTVP.json
index 88615b0..f94cab2 100644
--- a/TimeseriesTVP.json
+++ b/TimeseriesTVP.json
@@ -21,7 +21,7 @@
           "$ref":"http://raw.githubusercontent.com/peterataylor/om-json/master/TimeseriesMetadata.json#/definitions/PointMetadata"
         }
       },
-      "additionalProperties":"false"
+      "additionalProperties":false
     },
     "TVPairCategory" : {
       "type":"object",
@@ -36,10 +36,11 @@
           "$ref":"http://raw.githubusercontent.com/peterataylor/om-json/master/Common.json#/definitions/vocabTerm"
         }
       },
-      "additionalProperties":"false"
+      "additionalProperties":false
     }
   },
   "properties": {
+  	"@context" : { "$ref": "http://raw.githubusercontent.com/peterataylor/om-json/master/Common.json#/definitions/@context" },
     "id": {
       "title": "id",
       "description": "Identifier for the time-series",
diff --git a/json-ld/Context.json b/json-ld/Context.json
new file mode 100644
index 0000000..721395e
--- /dev/null
+++ b/json-ld/Context.json
@@ -0,0 +1,13 @@
+"@context": {
+    "observedProperty": "http://def.seegrid.csiro.au/isotc211/iso19156/2011/observation#observedProperty",
+    "href": "@id",
+    "foi": "http://def.seegrid.csiro.au/isotc211/iso19156/2011/observation#featureOfInterest",
+    "id": "@id",
+    "phenomenonTime": "http://def.seegrid.csiro.au/isotc211/iso19156/2011/observation#phenomenonTime",
+    "instant": "@value",
+    "member": "http://def.seegrid.csiro.au/isotc211/iso19156/2011/observation#relatedObservation",
+    "procedure": "http://def.seegrid.csiro.au/isotc211/iso19156/2011/observation#Process",
+    "resultTime": "http://def.seegrid.csiro.au/isotc211/iso19156/2011/observation#resultTime",
+    "result": "http://def.seegrid.csiro.au/isotc211/iso19156/2011/observation#result",
+    "value": "@value"
+  }
diff --git a/ocean-acidification/Methodology.json b/ocean-acidification/Methodology.json
new file mode 100644
index 0000000..5633797
--- /dev/null
+++ b/ocean-acidification/Methodology.json
@@ -0,0 +1,33 @@
+{
+	"$schema": "http://json-schema.org/draft-04/schema#",
+	"id": "http://raw.githubusercontent.com/adamml/om-json/master/ocean-acidification/Methodology.json",
+	"title": "Methodology",
+	"description": "A description of a reference to, for example, a journal article and some descriptive parameters for an analytical methodology",
+	"type": "object",
+	"properties": {
+		"@context" : { "$ref": "http://raw.githubusercontent.com/peterataylor/om-json/master/Common.json#/definitions/@context" },
+		"id": {
+			"title": "id",
+			"description": "A unique identifier for this protocol",
+			"type": "string"
+		},
+		"reference": {
+			"title": "reference",
+			"description": "Either an object defining the academic literature reference or a URL linking to such an object",
+			"oneOf": [
+				{ "$ref" : "http://raw.githubusercontent.com/peterataylor/om-json/master/Common.json#/definitions/link" },
+				{ "$ref" : "http://raw.githubusercontent.com/adamml/om-json/master/ocean-acidification/Reference.json" }
+			]
+		},
+		"preparationStep": {
+			"title": "preparation step",
+			"description": "Either an object defining the sample preparation steps taken reference or a URL linking to such an object",
+			"oneOf": [
+				{ "$ref" : "http://raw.githubusercontent.com/peterataylor/om-json/master/Common.json#/definitions/link" },
+				{ "$ref" : "http://raw.githubusercontent.com/adamml/om-json/master/ocean-acidification/PreparationStep.json" }
+			]
+		}
+	},
+	"required": [ "id"],
+	"additionalProperties": false
+}
diff --git a/ocean-acidification/PreparationStep.json b/ocean-acidification/PreparationStep.json
new file mode 100644
index 0000000..6a02059
--- /dev/null
+++ b/ocean-acidification/PreparationStep.json
@@ -0,0 +1,57 @@
+{
+	"$schema": "http://json-schema.org/draft-04/schema#",
+	"id": "http://raw.githubusercontent.com/adamml/om-json/master/ocean-acidification/PreparationStep.json",
+	"title": "PreparationStep",
+	"description": "Describes the sample preparation",
+	"type": "object",
+	"properties": {
+		"@context" : { "$ref": "http://raw.githubusercontent.com/peterataylor/om-json/master/Common.json#/definitions/@context" },
+		"id": {
+			"title": "id",
+			"description": "A unique identifier for this sample preparation",
+			"type": "string"
+		},
+		"fixation": {
+			"title": "fixation",
+			"description": "Either a plain text description of the fixation method, or a URL to a description of the fixation method in a controlled vocabulary entry",
+			"oneOf": [
+				{ "$ref" : "http://raw.githubusercontent.com/peterataylor/om-json/master/Common.json#/definitions/link" },
+				{ "type" : "string" }
+			]
+		},
+		"storage": {
+			"title": "storage",
+			"description": "Either a plain text description of the storage method, or a URL to a description of the storage method in a controlled vocabulary entry",
+			"oneOf": [
+				{ "$ref" : "http://raw.githubusercontent.com/peterataylor/om-json/master/Common.json#/definitions/link" },
+				{ "type" : "string" }
+			]
+		},
+		"extraction": {
+			"title": "extraction",
+			"description": "Either a plain text description of the extraction method, or a URL to a description of the extraction method in a controlled vocabulary entry",
+			"oneOf": [
+				{ "$ref" : "http://raw.githubusercontent.com/peterataylor/om-json/master/Common.json#/definitions/link" },
+				{ "type" : "string" }
+			]
+		},
+		"pretreatment": {
+			"title": "pretreatment",
+			"description": "Either a plain text description of the pretreatment method, or a URL to a description of the pretreatment method in a controlled vocabulary entry",
+			"oneOf": [
+				{ "$ref" : "http://raw.githubusercontent.com/peterataylor/om-json/master/Common.json#/definitions/link" },
+				{ "type" : "string" }
+			]
+		},
+		"analysis": {
+			"title": "analysis",
+			"description": "Either a plain text description of the analysis method, or a URL to a description of the analysis method in a controlled vocabulary entry",
+			"oneOf": [
+				{ "$ref" : "http://raw.githubusercontent.com/peterataylor/om-json/master/Common.json#/definitions/link" },
+				{ "type" : "string" }
+			]
+		}
+	},
+	"required": [ "id"],
+	"additionalProperties": false
+}
\ No newline at end of file
diff --git a/ocean-acidification/Protocol.json b/ocean-acidification/Protocol.json
new file mode 100644
index 0000000..d960545
--- /dev/null
+++ b/ocean-acidification/Protocol.json
@@ -0,0 +1,43 @@
+{
+	"$schema": "http://json-schema.org/draft-04/schema#",
+	"id": "http://raw.githubusercontent.com/adamml/om-json/master/ocean-acidification/Protocol.json",
+	"title": "Protocol",
+	"description": "A specialisation of O&M's process, initially defined for the analytical chemistry domain of the UNESCO-IOC Ocean Acidificiation project",
+	"type": "object",
+	"properties": {
+		"@context" : { "$ref": "http://raw.githubusercontent.com/peterataylor/om-json/master/Common.json#/definitions/@context" },
+		"id": {
+			"title": "id",
+			"description": "A unique identifier for this protocol",
+			"type": "string"
+		},
+		"instrument": {
+			"title": "instrument",
+			"description": "A URL linking to a controlled vocabulary term defining the instrument make and model used in this instance of the protocol",
+			"$ref" : "http://raw.githubusercontent.com/peterataylor/om-json/master/Common.json#/definitions/link"
+		},
+		"laboratory": {
+			"title": "laboratory",
+			"description": "A URL to a controlled vocabulary term defining the laboratory responsible for the observation made using this instance of the protocol",
+			"$ref" : "http://raw.githubusercontent.com/peterataylor/om-json/master/Common.json#/definitions/link"
+		},
+		"methodology": {
+			"title": "methodology",
+			"description": "Either an object or a URL giving a description of a reference to, for example, a journal article and some descriptive parameters for an analytical methodology",
+			"oneOf": [
+				{ "$ref" : "http://raw.githubusercontent.com/peterataylor/om-json/master/Common.json#/definitions/link" },
+				{ "$ref" : "http://raw.githubusercontent.com/adamml/om-json/master/ocean-acidification/Methodology.json" }
+			]
+		},
+		"quality": {
+			"title": "quality",
+			"description": "Either an object or a URL giving a description of the quality (limits of detection, accuracy, precision, uncertainty) of an analytical protocol",
+			"oneOf": [
+				{ "$ref" : "http://raw.githubusercontent.com/peterataylor/om-json/master/Common.json#/definitions/link" },
+				{ "$ref" : "http://raw.githubusercontent.com/adamml/om-json/master/ocean-acidification/Quality.json" }
+			]
+		}
+	},
+	"required": [ "id", "methodology","instrument","laboratory"],
+	"additionalProperties": false
+}
diff --git a/ocean-acidification/Quality.json b/ocean-acidification/Quality.json
new file mode 100644
index 0000000..cce2adc
--- /dev/null
+++ b/ocean-acidification/Quality.json
@@ -0,0 +1,49 @@
+{
+	"$schema": "http://json-schema.org/draft-04/schema#",
+	"id": "http://raw.githubusercontent.com/adamml/om-json/master/ocean-acidification/Quality.json",
+	"title": "Quality",
+	"description": "A description of the quality (limits of detection, accuracy, precision, uncertainty) of an analytical protocol",
+	"type": "object",
+	"properties": {
+		"@context" : { "$ref": "http://raw.githubusercontent.com/peterataylor/om-json/master/Common.json#/definitions/@context" },
+		"id": {
+			"title": "id",
+			"description": "A unique identifier for this protocol",
+			"type": "string"
+		},
+		"limitOfDetection": {
+			"title": "limit of detection",
+			"description": "Either a URL or a string describing the limit of detection for the analytical method",
+			"oneOf": [
+				{ "$ref" : "http://raw.githubusercontent.com/peterataylor/om-json/master/Common.json#/definitions/link" },
+				{ "type" : "string" }
+			]
+		},
+		"accuracy": {
+			"title": "accuracy",
+			"description": "Either a URL or a string describing the accuracy of the analytical method",
+			"oneOf": [
+				{ "$ref" : "http://raw.githubusercontent.com/peterataylor/om-json/master/Common.json#/definitions/link" },
+				{ "type" : "string" }
+			]
+		},
+		"precision": {
+			"title": "precision",
+			"description": "Either a URL or a string describing the precision of the analytical method",
+			"oneOf": [
+				{ "$ref" : "http://raw.githubusercontent.com/peterataylor/om-json/master/Common.json#/definitions/link" },
+				{ "type" : "string" }
+			]
+		},
+		"uncertainty": {
+			"title": "uncertainty",
+			"description": "Either a URL or a string describing the uncertainty of the analytical method",
+			"oneOf": [
+				{ "$ref" : "http://raw.githubusercontent.com/peterataylor/om-json/master/Common.json#/definitions/link" },
+				{ "type" : "string" }
+			]
+		}
+	},
+	"required": [ "id"],
+	"additionalProperties": false
+}
diff --git a/ocean-acidification/Reference.json b/ocean-acidification/Reference.json
new file mode 100644
index 0000000..34da288
--- /dev/null
+++ b/ocean-acidification/Reference.json
@@ -0,0 +1,33 @@
+{
+	"$schema": "http://json-schema.org/draft-04/schema#",
+	"id": "http://raw.githubusercontent.com/adamml/om-json/master/ocean-acidification/Reference.json",
+	"title": "Reference",
+	"description": "Describes the recommended citation text for a reference, and provides a link to the journal paper or methodology description",
+	"type": "object",
+	"properties": {
+		"@context" : { "$ref": "http://raw.githubusercontent.com/peterataylor/om-json/master/Common.json#/definitions/@context" },
+		"id": {
+			"title": "id",
+			"description": "A unique identifier for this reference",
+			"type": "string"
+		},
+		"doiOrWebAddress": {
+			"title": "doi",
+			"description": "A formal Digital Object Identifier, or a plain web link, to a resource describing the protocol",
+
+				"oneOf": [{ "$ref" : "http://raw.githubusercontent.com/peterataylor/om-json/master/Common.json#/definitions/doi" },{ "$ref" : "http://raw.githubusercontent.com/peterataylor/om-json/master/Common.json#/definitions/link" }]
+		},
+		"citation": {
+			"title": "citation",
+			"description": "A plain text representation of the recommended citation text to be used in referencing the protocol description",
+			"type": "string"
+		},
+		"informalReference": {
+			"title": "informalReference",
+			"description": "For use only if a non-citable and non-machine referenceable document exists, a written description may be provided",
+			"type": "string"
+		}
+	},
+	"required": [ "id"],
+	"additionalProperties": false
+}
diff --git a/ocean-acidification/examples/Observation_Example.json b/ocean-acidification/examples/Observation_Example.json
new file mode 100644
index 0000000..1e344cb
--- /dev/null
+++ b/ocean-acidification/examples/Observation_Example.json
@@ -0,0 +1,26 @@
+{
+	"id": "exampleTotalAlkalinity",
+	"featureOfInterest": {"href": "http://vocab.nerc.ac.uk/collection/C19/current/1_6/"},
+	"phenomenonTime": {"instant": "2015-09-23T12:51:11.421Z"},
+	"type": "measure",
+	"result": {"value": 12, "uom":"http://vocab.nerc.ac.uk/collection/P06/current/UEQL/"},
+	"resultTime": "2015-10-23T11:10:10Z",
+	"observedProperty": {"href": "http://vocab.nerc.ac.uk/collection/P01/current/ALKYZZXX/"},
+	"procedure": {
+		"id": "exampleTotalAlkalinity",
+		"methodology": {
+			"id": "someChemicalAnalysisMethod",
+			"reference": {"href": "https://raw.githubusercontent.com/adamml/om-json/master/ocean-acidification/examples/Reference_Examle.json"},
+			"preparationStep": {
+				"id": "The Prepartory work for method above",
+				"analysis": {"href": "http://vocab.nerc.ac.uk/collection/S04/current/S0475/"}
+			}
+		},
+        	"instrument": {"href": "http://vocab.nerc.ac.uk/collection/L22/current/TOOL0481/"},
+        	"laboratory": {"href": "SDN:EDMO:396"},
+		"quality": {
+			"id": "A general example of how quality could work",
+			"limitOfDetection": "0 - 15"
+		}
+	}
+}
diff --git a/ocean-acidification/examples/Reference_Example.json b/ocean-acidification/examples/Reference_Example.json
new file mode 100644
index 0000000..d98fa1b
--- /dev/null
+++ b/ocean-acidification/examples/Reference_Example.json
@@ -0,0 +1,6 @@
+{
+	"id": "Leadbetter&Vodden2015",
+	"doiOrWebAddress": {"doi": "10.1080/17538947.2015.1033483"},
+	"citation": "Leadbetter, A.M. & Vodden, P.N. (2015). Semantic linking of complex properties, monitoring processes and facilities in web-based representations of the environment. International Journal of Digital Earth.",
+	"informalReference": "Leadbetter & Vodden, 2015."
+}