[OASIS Issue Tracker] Updated: (ODATA-577) Do we need a way to distinguish between properties that are omitted due to being aggregated away versus those that don't apply (i.e., in a concatenated result)?

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     [ http://tools.oasis-open.org/issues/browse/ODATA-577?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Ralf Handl updated ODATA-577:
-----------------------------

    Environment: [Proposed][Applied]
       Proposal: 
@odata.context allows to identify and distinguish all cases: aggregation result, rollup entities, concat result.

- The @odata.context describes the properties from the input set that remain in the result after aggregation. Any property of the input/expanded sets not listed here has been aggregated away.

- In rollup entities, one or more of those properties are omitted. Comparing an instance with the surrounding @odata.context, the absence of a property in an instance classifies this entity as rollup entities, because there is no other way how a property could get lost.

- Concat combines two aggregated results with potentially different structures as a single result collection. This inhomogeneous structure cannot be described with a single context URL at the level of the collection. If the two partial results deviate structurally, the current JSON spec requires a provider to apply @odata.context at entity instance level for every entity. This is not efficient if done for a large set of such instances, but we do not see any other option with the current capabilities of @odata.context. On the other hand, every part of the result structure is clearly defined, so there's need to further distinguish the cases mentioned in the issue.

> Do we need a way to distinguish between properties that are omitted due to being aggregated away versus those that don't apply (i.e., in a concatenated result)?
> ----------------------------------------------------------------------------------------------------------------------------------------------------------------
>
>                 Key: ODATA-577
>                 URL: http://tools.oasis-open.org/issues/browse/ODATA-577
>             Project: OASIS Open Data Protocol (OData) TC
>          Issue Type: Bug
>          Components: OData Extension for Data Aggregation 
>    Affects Versions: V4.0_CSD01
>         Environment: [Proposed][Applied]
>            Reporter: Michael Pizzo
>             Fix For: V4.0_CSD02
>
>
> There appear to be (at least) two ways a property may be omitted from an aggregated result:
> 1) The property may be omitted because it has been aggregated away (i.e., in a rollup)
> 2) The property may be omitted because an operator has been applied (i.e., concat) that leaves certain properties undefined for certain rows
> Do we need a property annotation for either (or both) so that clients can distinguish between properties being omitted because they were aggregated away versus because they didn't apply?

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