[OASIS Issue Tracker] Commented: (ODATA-398) Define canonical function as a path segment that allows retrieving an entity by its id

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    [ http://tools.oasis-open.org/issues/browse/ODATA-398?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=33515#action_33515 ] 

Ralf Handl commented on ODATA-398:
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Why do we need the cast segment? 

The returned entity will contain this type information anyway, and it also will contain all its properties (if not projected with $select), so there's little benefit in adding a cast segment. It will shorten the response to a 404 Not Found with an empty body, at the cost of not being able to distinguish between "this entity does not exist" and "this entity exists and is not of the requested type".

I think we should NOT allow this cast segment as it adds complexity.

> Define canonical function as a path segment that allows retrieving an entity by its id
> --------------------------------------------------------------------------------------
>
>                 Key: ODATA-398
>                 URL: http://tools.oasis-open.org/issues/browse/ODATA-398
>             Project: OASIS Open Data Protocol (OData) TC
>          Issue Type: Improvement
>          Components: OData ABNF Construction Rules, OData Protocol , OData URL Conventions 
>    Affects Versions: V4.0_CSD01
>         Environment: [Proposed]
>            Reporter: Michael Pizzo
>             Fix For: V4.0_CSD02
>
>
> Ids are the primary way to reference an instance in OData; they are used in relationships, in deltas, and can take the place of instances in payloads. We recommend, but do not require that ids be dereferenceable.
> Clients need a dependable way to get from an id to a reference, whether or not the reference is dereferencable. Although they could construct a query if they know the root set the id comes from, it would be useful and more discoverable to introduce a canonical query function, at the service root, for returning an instance given its id.
> Note that, since the id is likely to contain illegal characters, we have to pass the id as a query option, and will need to double single quotes in reference
> Options:
> GET ~myservice/getbyid(@id)?@id='.....'
> GET ~myservice/$getbyid?@id='.....'

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