[OASIS Issue Tracker] (ODATA-1062) Revise UML model for OData Metamodel

[OASIS Issues Tracker <workgroup_mailer@lists.oasis-open.org>]

    [ https://issues.oasis-open.org/browse/ODATA-1062?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=66046#comment-66046 ] 

George Ericson commented on ODATA-1062:
---------------------------------------

Some thoughts from 20170504 call.
- Service document is the service's entity container
- Kinds of Type are Term, ComplexType, EnumType, PrimitiveType
- Kinds of ComplexType are EntityType, --EntityContainer--
- Kinds of Property are Annotation, Enumeration, Primitive, Complex, NavigationProperty, and EntityContainingProperty
- Kinds of EntityContainingProperty are Entity Set (array) and Singleton (scalar)
- NavigationProperty are either explicitly or implicitly bound to an EntityContainingProperty having the same multiplicity
- If not explicitly declared (ContainsTarget=True or NavigationPropertyBinding) the corresponding EntityContainingProperty is an implicit member of the EntityContainer
---- If ContainsTarget=True, the EntityContainingProperty is a member of the properties type.

> Revise UML model for OData Metamodel 
> -------------------------------------
>
>                 Key: ODATA-1062
>                 URL: https://issues.oasis-open.org/browse/ODATA-1062
>             Project: OASIS Open Data Protocol (OData) TC
>          Issue Type: Improvement
>          Components: CSDL JSON , CSDL XML, Implementing OData, New in OData, Vocabularies
>    Affects Versions: V4.0_CSD01
>            Reporter: George Ericson
>            Assignee: George Ericson
>             Fix For: V4.0_CSD02
>
>
> Various aspects of OData seem unclear or redundant.  A formal UML model for the OData metamodel can be used to clarify and simplify OData.   
> The existing metamodel defined by 'MetadataService.xml' contains much of what is needed, but has some issues, such as:
> - The MetadataContainer element refers to metadata elements, but should be referencing instances of metadata elements (i.e. schema).  
> - Various language elements are included, (eg. ne and eq)
> The included proposal started from scratch out of a need to understand several concepts, including the semantics of Singletons and EntitySets.  It needs to be rationalized with the existing 'MetadataService.xml' .  It is preliminary and needs review and refinement.  It is expressed in CSDL XML.  (See https://www.oasis-open.org/apps/org/workgroup/odata/download.php/60420/OdataMetamodel.xml.)   UML diagrams are provided that illustrate this proposal.  (See: https://www.oasis-open.org/apps/org/workgroup/odata/download.php/60421/OdataMetamodel.pdf)
> An advantage of the UML model is that it expresses the Odata metamodel in precise terms.  Constraints and requirements on the various elements of the model are expressed normatively using the UML model together with UML Object Constraing Language (OCL) statements.  An added Term supports this.
> The various schema definition languages CSDL XML, CSDL JSON, and others should conform to the OData metamodel.



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