Merge branch 'master' into CivilSpatial

Domains/0-Core/BisCore.ecschema.xml

@@ -1034,6 +1034,19 @@
         </ECProperty>
         <ECProperty propertyName="Format" typeName="string" displayLabel="Format" description="The format of the external repository."/>
     </ECEntityClass>
+    <ECEntityClass typeName="RepositoryInfoAspect" displayLabel="Repository Info Aspect" modifier="None" description="A bis:ElementUniqueAspect that identifies a bis:Element as one of the roots of a *channel*, specified by its *channel-key*, which is a subset of the overall model-hierarchy and associated data, that is independently maintained.">
+        <BaseClass>ElementUniqueAspect</BaseClass>
+        <ECProperty propertyName="OriginatingSystem" typeName="string" displayLabel="Originating System" description="Name and optionally version of the software application or tool that created data in the External DataSource referenced through the owning RepositoryLink"/>
+    </ECEntityClass>
+    <ECRelationshipClass typeName="RepositoryLinkOwnsInfoAspect" strength="embedding" modifier="None">
+        <BaseClass>ElementOwnsUniqueAspect</BaseClass>
+        <Source multiplicity="(1..1)" roleLabel="owns" polymorphic="true">
+            <Class class="RepositoryLink"/>
+        </Source>
+        <Target multiplicity="(0..1)" roleLabel="is owned by" polymorphic="true">
+            <Class class="RepositoryInfoAspect"/>
+        </Target>
+    </ECRelationshipClass>
 
     <ECEntityClass typeName="EmbeddedFileLink" displayLabel="Embedded File Link" description="A bis:EmbeddedFileLink is a bis:LinkElement that links to a file embedded within the iModel.">
         <BaseClass>LinkElement</BaseClass>
@@ -1873,6 +1886,7 @@
     <ECEntityClass typeName="ChannelRootAspect" displayLabel="Channel Root Aspect" modifier="Sealed" description="A bis:ElementUniqueAspect that identifies a bis:Element as one of the roots of a *channel*, specified by its *channel-key*, which is a subset of the overall model-hierarchy and associated data, that is independently maintained.">
         <BaseClass>ElementUniqueAspect</BaseClass>
         <ECProperty propertyName="Owner" typeName="string" description="Channel-key of the channel"/>
+        <ECProperty propertyName="Version" typeName="string" description="Semantic version of the data-organization and default content in the channel, set by the Owner that last edited it."/>
     </ECEntityClass>
     <ECRelationshipClass typeName="ElementOwnsChannelRootAspect" strength="embedding" modifier="None">
         <BaseClass>ElementOwnsUniqueAspect</BaseClass>

Domains/0-Core/BisCore.remarks.md

@@ -396,7 +396,12 @@ Applications create channels to define portions of the model-hierarchy that they
 
 Each Element (typically a `Subject` or `InformationPartitionElement`) that owns a `ChannelRootAspect` defines a root of the model-hierarchy that is included in a particular *channel*. It recursively descends down through `ElementOwnsChildElements` and `ModelModelsElement` relationships to include all of the child elements and sub-models into the specified *channel*. A *channel* is conceptually identified by its _Channel Key_ value of the `Owner` property of a `ChannelRootAspect`. 
 
-There may be more than one root `Subject`s or `InformationPartitionElement`s in a model-hierarchy that are included in the same *channel*. In that case, each `Subject` or `InformationPartitionElement` instance specifies the same _Channel Key_ value in their `ChannelRootAspect`. 
+Applications can optionally use the `ChannelRootAspect.Version` property in order to assign a _semantic version_ number to the data-organization in a *channel*. _Semantic versioning_ aims at efficiently advertising read and write backwards-compatibility with respect to previous versions of the owning Application of a *channel*. 
+
+_Semantic versioning_ of *channels* follows the "[read-version].[write-version].[minor-version]" format.
+- [read-version] is incremented when the data-organization of a *channel* is changed in ways that older versions of an Application cannot safely understand it for reading purposes.
+- [write-version] is incremented when the data-organization of a *channel* is changed in ways that it is not safe for older versions of an Application to add, modify or delete data in it.
+- [minor-version] is incremented when the data-organization of a *channel* is changed in ways that older versions of an Application can still safely read it or write to it.
 
 Note that *Channels* do not nest. That is, once a `Subject` or `InformationPartitionElement` instance defines a root to be included in a particular *channel*, no descendant Element of such root in the subject-hierarchy can be used to define a root for a different *channel*.