[OASIS Issue Tracker] (ODATA-1059) Improve specification and use of NavigationProperties, EntitySets, and Singletons

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

     [ https://issues.oasis-open.org/browse/ODATA-1059?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Ralf Handl updated ODATA-1059:
------------------------------

    Environment:     (was: Any)

> Improve specification and use of NavigationProperties, EntitySets, and Singletons
> ---------------------------------------------------------------------------------
>
>                 Key: ODATA-1059
>                 URL: https://issues.oasis-open.org/browse/ODATA-1059
>             Project: OASIS Open Data Protocol (OData) TC
>          Issue Type: Improvement
>          Components: ABNF Construction Rules, CSDL JSON , CSDL XML, Implementing OData
>            Reporter: George Ericson
>            Assignee: George Ericson
>              Labels: Extension, Usability, request_tc_discussion
>             Fix For: V4.02_WD01
>
>
> There is significant confusion over the role and semantics of Singletons and EntitySets.  For example, since Nullable is not an attribute, it is assumed that they must have a value, but implementors are also assuming that if a particular Singleton or EntitySet is not implemented, then a value need not be returned.
> Observations on Singletons and EntitySets from an OData metamodel point of view:
> 1) A Singleton is a scalar Property with a Type that is an EntityType.
> 2) An EntitySet is an array Property with a Type that is an EntityType.
> 3) A NavigationProperty with ContainsTarget="True" is a scalar or array Property with a Type that is an EntityType.
> 4) A NavigationProperty with ContainsTarget="False" is an association end with a Type that is an EntityType.
> The overlap of 1, 2, and 3 is a source of great confusion.  Additionally the reasons for variations in semantics of these metatypes are not clear.  (i.e. missing Nullable attribute.)



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