JSON Format Transport the ETag for a collection-valued navigation property in its containing entity as control information on the navigation property: { "@context" : "http: //host/service/$metadata#Orders/$entity" , "@id" : "Orders(1234)" , "@etag" : "W/\" MjAxMy0wNS0yN1QxMTo1OFo=\"", "ID" : 1234, "Items@etag" : "W/\" MjAxOS0wMy0xMlQxMDoyMlo=\"" } Note: the collection ETag for a navigation property may or may not be identical to the ETag of the container entity, the example shows a different ETag for the Orders collection. Services MAY include these, just as they MAY include the entity @etag control information. Up to the server when to do it. based e.g. on computational complexity. Annotate Navigation Properties Extend type Capabilities.NavigationPropertyRestriction with property OptimisticConcurrencyControl of type Edm.Boolean , default value false . Note: this differs from the existing term Core.OptimisticConcurrency which is a collection of property paths, using an empty collection for "tagging" without revealing which properties influence the calculated ETag. Protocol Add POST to the list of methods in sections 8.2.4 Header If-Match and 8.2.5 Header If-None-Match. Mention collection ETags in section 11.4.1.1 Use of ETags for Avoiding Update Conflicts.

https://github.com/oasis-tcs/odata-vocabularies/pull/43/files https://www.oasis-open.org/committees/download.php/64925/odata-json-format-v4.01-wd06-2019-03-15.docx https://www.oasis-open.org/committees/download.php/64927/odata-v4.01-wd06-part1-protocol-2019-03-21a.docx