[OASIS Issue Tracker] Created: (ODATA-392) Expanded Navigation Properties should be implicitly added to $select

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

Expanded Navigation Properties should be implicitly added to $select
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                 Key: ODATA-392
                 URL: http://tools.oasis-open.org/issues/browse/ODATA-392
             Project: OASIS Open Data Protocol (OData) TC
          Issue Type: Improvement
          Components: OData URL Conventions 
    Affects Versions: V4.0_CSD01
         Environment: [Proposed]
            Reporter: Michael Pizzo
            Priority: Minor
             Fix For: V4.0_CSD02


We had a long discussion in Boston over whether $expanded navigation properties were implicitly added to a $select.

The argument against doing this was that it was more correct and simpler to keep the two separate; $expand is part of defining the extent of the result, and $select is used to say which properties are returned. Implicitly adding the expanded navigation properties to the $select would mean a serializer would have to look both in $select and $expand to figure out which properties to put on the wire.

The argument for implicitly adding $expanded properties to $select was that it wasn't meaningful to do a $expand if you weren't going to return the expanded property, so why require the client to add it to the $select?

As strong as the first argument is, we have empirical evidence that customers *do* get tripped up today by having to add the $expanded navigation properties to $select. OData needs to be simple and predictable, so though I like the cleanliness of keeping them separate I propose we follow the principle of least astonishment by making the expanded navigation properties implicit in the $select.

Note that this means the metadata url has to specify selected or expanded properties, and can't just copy the $select, but we already moved away from just using the $select in the metadataurl in order to handle selects on expanded properties w/o going back to path notation.

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