Add a semantic custom-attribute for TypeDefinition relationships.

Domains/0-Core/BisCore.ecschema.xml

@@ -6,7 +6,7 @@
 <ECSchema schemaName="BisCore" alias="bis" version="01.00.17" xmlns="http://www.bentley.com/schemas/Bentley.ECXML.3.2" displayLabel="BIS Core" description="The BIS core schema contains classes that all other domain schemas extend.">
 
     <ECSchemaReference name="CoreCustomAttributes" version="01.00.03" alias="CoreCA"/>
-    <ECSchemaReference name="BisCustomAttributes" version="01.00.00" alias="bisCA"/>
+    <ECSchemaReference name="BisCustomAttributes" version="01.00.01" alias="bisCA"/>
     <ECSchemaReference name="ECDbMap" version="02.00.00" alias="ecdbmap"/>
     <ECSchemaReference name="ECDbSchemaPolicies" version="01.00.00" alias="ecdbpol"/>
 
@@ -675,6 +675,9 @@
 
     <ECRelationshipClass typeName="GeometricElement2dHasTypeDefinition" strength="referencing" modifier="Abstract">
         <!-- @see GeometricElement2d.TypeDefinition ECNavigationProperty -->
+        <ECCustomAttributes>
+            <TypeDefinitionRelationship xmlns="BisCustomAttributes.01.00.01"/>
+        </ECCustomAttributes>
         <Source multiplicity="(0..*)" roleLabel="is of type" polymorphic="true">
             <Class class="GeometricElement2d" />
         </Source>
@@ -694,6 +697,9 @@
 
     <ECRelationshipClass typeName="GeometricElement3dHasTypeDefinition" strength="referencing" modifier="Abstract">
         <!-- @see GeometricElement3d.TypeDefinition ECNavigationProperty -->
+        <ECCustomAttributes>
+            <TypeDefinitionRelationship xmlns="BisCustomAttributes.01.00.01"/>
+        </ECCustomAttributes>
         <Source multiplicity="(0..*)" roleLabel="is of type" polymorphic="true">
             <Class class="GeometricElement3d" />
         </Source>

Domains/0-Core/Functional.ecschema.xml

@@ -6,7 +6,7 @@
 <ECSchema schemaName="Functional" alias="func" version="01.00.05" xmlns="http://www.bentley.com/schemas/Bentley.ECXML.3.2" description="The Functional schema defines common base classes to be used by discipline-specific functional domains.">
 
     <ECSchemaReference name="CoreCustomAttributes" version="01.00.04" alias="CoreCA"/>
-    <ECSchemaReference name="BisCustomAttributes" version="01.00.00" alias="bisCA"/>
+    <ECSchemaReference name="BisCustomAttributes" version="01.00.01" alias="bisCA"/>
     <ECSchemaReference name="BisCore" version="01.00.15" alias="bis"/>
     <ECSchemaReference name="ECDbMap" version="02.00.00" alias="ecdbmap"/>
 
@@ -93,6 +93,9 @@
     </ECEntityClass>
 
     <ECRelationshipClass typeName="FunctionalElementIsOfType" strength="referencing" modifier="None" description="A type-instance relation; one that indicates that the specific func:FunctionalElement is an instance of the defined func:FunctionalType.">
+        <ECCustomAttributes>
+            <TypeDefinitionRelationship xmlns="BisCustomAttributes.01.00.01"/>
+        </ECCustomAttributes>
         <Source multiplicity="(0..*)" roleLabel="is of type" polymorphic="true">
             <Class class="FunctionalElement" />
         </Source>

SchemaInventory.json

@@ -4663,7 +4663,7 @@
       "name": "BisCustomAttributes",
       "path": "Standard\\BisCustomAttributes.ecschema.xml",
       "released": false,
-      "version": "01.00.00",
+      "version": "01.00.01",
       "comment": "Working Copy",
       "sha1": "",
       "author": "Diego.Diaz",

Standard/BisCustomAttributes.ecschema.xml

@@ -3,7 +3,7 @@
 |  * Copyright (c) Bentley Systems, Incorporated. All rights reserved.
 |  * See LICENSE.md in the project root for license terms and full copyright notice.
 ======================================================================================= -->
-<ECSchema schemaName="BisCustomAttributes" alias="bisCA" version="01.00.00" description="Custom attributes to indicate BIS concepts." displayLabel="BIS Custom Attributes" xmlns="http://www.bentley.com/schemas/Bentley.ECXML.3.2">
+<ECSchema schemaName="BisCustomAttributes" alias="bisCA" version="01.00.01" description="Custom attributes to indicate BIS concepts." displayLabel="BIS Custom Attributes" xmlns="http://www.bentley.com/schemas/Bentley.ECXML.3.2">
     <ECEnumeration typeName="SchemaLayer" backingTypeName="string" isStrict="true" description="Defines the layers in the BIS schema hierarchy.">
         <ECEnumerator name="Core"               displayLabel="Core"                value="Core"               description="Layer for schemas that define the most fundamental concepts and key organizational strategies for all other BIS schemas."/>
         <ECEnumerator name="Common"             displayLabel="Common"              value="Common"             description="Layer for schemas that define abstract concepts and patterns used by multiple disciplines."/>
@@ -15,4 +15,6 @@
     <ECCustomAttributeClass typeName="SchemaLayerInfo" appliesTo="Schema" modifier="Sealed" description="Declares the target layer in the BIS schema hierarchy for a schema.">
         <ECProperty propertyName="Value" typeName="SchemaLayer" description="Layer in the BIS schema hierarchy that a schema targets." />
     </ECCustomAttributeClass>
+
+    <ECCustomAttributeClass typeName="TypeDefinitionRelationship" appliesTo="RelationshipClass" description="Identifies a relationship class that associates Elements with their corresponding TypeDefinition instance." displayLabel="Type-Definition Relationship" modifier="Sealed"/>
 </ECSchema>

Standard/BisCustomAttributes.remarks.md

@@ -37,4 +37,10 @@ Other technology-specific schemas not meant to be referenced by other schemas be
 
 ### SchemaLayerInfo
 
-BIS schemas should be tagged with the `SchemaLayerInfo` `CustomAttribute` to enable validation and error checking related to schema-references.
+BIS schemas should be tagged with the `SchemaLayerInfo` `CustomAttribute` to enable validation and error checking related to schema-references.
+
+### TypeDefinitionRelationship
+
+Under this _type definition_ semantics, the element at the source end of the relationship is subclassified by the element at the target end (its Type-Definition). That is, the latter provides a finer classification of the former than what its _element class_ targets. Furthermore, any business properties and their values captured by the element at the target end of the relationship are considered shared among all the elements at the source of the relationship.
+
+Note that the `TypeDefinitionRelationship` `CustomAttribute` implies that a relationship tagged with it uses a _referencing_ **strenght**, has a _0..*_ **multiplicity** on its source end, and a _0..1_ **multiplicity** on its target end-point.