ETags in responses with return=minimal

[HeikoTheissen]

OData-Protocol, section 11.4.3 states

If the service uses ETags for optimistic concurrency control, the entities in the response MUST include ETags.

Does this also apply if the Preference: return=minimal is applied? The OData specification of this preference (and even more the underlying RFC 7240) seems to leave open the possiblity of a response with

200 OK
Preference-Applied: return

and only keys and etags in the payload.

Clarify this in the OData specification.

[mikepizzo]

2025/1/8 Meeting:
Returning just the keys and etags in a response to return=minimal is a valid response. However, that doesn't provide the ability for the user to specify that this is the desired behavior (i.e., to return the ids/keys versus the etags).

If we want the client to have a way to specify that they want just ids/keys (and etags, as appropriate), then we could add a new preference for returning just ids/keys (and etags, as appropriate). We could also consider adding a $keys (or $ids) that can be specified in $select in order to request all key properties or the odata id.