From W3C Wiki
Schema.org and OData
This page is about the use of schema.org vocabularies with the OData protocol (see also wikipedia). This will allow for better information flow between OData and other systems, and enable OData users to make use of existing schema.org vocabulary. OData defines both XML and JSON representations, but does not itself include any built-in vocabularies.
OData defines a RESTful interface for working with data on the web. The newest version of OData defines a feature called "Vocabularies", which is a way to annotate data or metadata exposed by an OData Service. A common use for this feature will be to define shared vocabularies for common ontologies such as Sales (with Customers, SalesOrder, Product, etc.), Movies (with Title, Actor, Director, ....), or Calendars (with Event, Venue, …). RDFa 1.1 Lite defines an alternate encoding to HTML5's Microdata which “…will allow publishers to focus more on what they want to say with their data, rather than on the details of its specific encoding as markup.” In the same way, defining an OData Vocabulary encoding of the Schema.org schemas facilitates the understanding and even transformation of data across these different encodings.
A more detailed discussion document from the Microsoft OData team is also available; see attached PDF.
Note: this is a work-in-progress; the final form of the encoding is not yet fixed.