[OASIS Issue Tracker] (ODATA-735) Enhance the CSDL for instance annotations

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

    [ https://issues.oasis-open.org/browse/ODATA-735?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=62975#comment-62975 ] 

Michael Pizzo commented on ODATA-735:
-------------------------------------

Both of these proposals fill in a conceptual gap, but in discussing client scenarios we had difficulty coming up with compelling use cases where they would be valuable.

We are already questioning the value of "AppliesTo" because it has been difficult to get right/maintain/extend. It is somewhat useful in metadata designers, since it gives the designer the ability to create a dropdown of the applicable terms, but seems less valuable for instance annotations.

Similarly, having an annotation that specifies which instance annotations may be returned didn't seem like something a client would typically alter behavior based upon. Presumably the service would always be allowed to return instance annotations outside of this list (just as it can apply metadata annotations outside of those specified by "AppliesTo"), so the client would be prepared to handle arbitrary annotations anyway. If there was a particular set of annotations a client did want, they would typically express those in a preference header. Similarly, if there was a specific set of annotations a client didn't want, they would exclude those through a preference header. If a client wanted only a particular set of annotations, they would include those and exclude *. The scenario where the client first looked to see what annotations were available, and then included or excluded those they wanted (or didn't want) seemed unnecessarily complex, and we couldn't think of any other scenarios were the client would use this information.

Consensus in 2016-7-21 was to close with no action, but wanted to follow up with Matt, who was not on the call, to make sure he didn't have a particular use case that required this additional information.

> Enhance the CSDL for instance annotations
> -----------------------------------------
>
>                 Key: ODATA-735
>                 URL: https://issues.oasis-open.org/browse/ODATA-735
>             Project: OASIS Open Data Protocol (OData) TC
>          Issue Type: Improvement
>          Components: OData CSDL
>    Affects Versions: V4.0_ERRATA01
>         Environment: Annotations
>            Reporter: Matthew Borges
>            Assignee: Matthew Borges
>            Priority: Minor
>              Labels: Usability
>             Fix For: V4.01_WD01
>
>
> There are two parts to this issue:
> 1) The AppliesTo attribute of edm:Term can only be used to refer to metadata-based annotations.  It would be desirable to enhance this so that it can also be used for instance annotations.  I discussed this with Ralf, and he suggested one approach would be to update AppliesTo to also allow terms like:
> TypeInstance, CollectionInstance, EntityTypeInstance, ReferenceInstance, etc. or even just Instance
> 2) There is currently no way to include in the metadata document what instance annotations can be expected for particular types.  We should also allow this information in the metadata document.



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