Peter Qian, a developer on the data services team, has posted a two part series on the versioning headers used by ADO.NET Data Services to ensure a client or server never misinterprets a payload or URI.  You can check out his posts here:

Part 1 - Versioning Protocol of Astoria

Part 2 - Versioning Protocol of Astoria II

 

-Mike Flasko

ADO.NET Data Services, Program Manager