Often times large sets of data have a relatively small number of changes throughout a given period of time. In such cases, clients typically want to see only the changes to the data without having to retrieve the entire large set of data, for example, to apply changes to a local set of results.

The referenced presentation, presented at the first OData TC meeting in July, describes thoughts and requirements around a "delta" protocol to provide a hypermedia-driven solution for retrieving changes to a given set of data: https://www.oasis-open.org/apps/org/workgroup/odata/download.php/46575/OData%20Deltas.pptx.

A complete proposal would define the specific changes to [OData-Core] to support deltas.