From my understanding, OData v3.0 are supported by Windows Azure, and OData v4.0 is expected to become an OASIS Standard in 2013.
The OASIS OData version 4.0 specification is based on the popular OData version 3.0. OData version 4.0 defines data model changes to significantly simplify and expand how relationships are expressed and used as well as how metadata is described and partitioned,
expanded query capabilities for inline collections and fulltext search, and extended functionality for change tracking and asynchronous processing.
For more detail, please refer to this article:
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Marked as answer by3D HD SoftThursday, September 12, 2013 2:27 PM