What is WCF DataServices (OData)

Databases are growing on variety of systems, clients and application are growing while data consumption is increasing, there is a great demand for terabytes of data everyday.
Data consumers need data in various formats like XML, JSON ATOM (Xml based feed format), etc.

To overcome such a massive data demand Microsoft launched WCF DataServices Framework using Open data protocol (OData)

• formerly known as ADO.Net Data Services
• uniform way of returning data such as XML, JSON ATOM (Xml based feed format), etc. 
• uniform URL conventions to navigate, paginate, sorting, filtering.
• provides client libraries for Windows Phone 7, Silverlight, Sharepoint, SQL Server 2008, MS Excel Pivot, PHP, Java.
• works on wcf capabilities to expose data as web services
• enables to expose data and manipulate in the RESTful way to perform CRUD operations.
• data is transported on HTTP and agents could simply use its methods GET, POST, PUT and DELETE.
• you could write LINQ queries and access data, under the cover it converts the LINQ query to a uri or vice-versa.
• out of the box Sharepoint 2010 exposes all its data via Odata formats.
• data could be shared at large between systems and cross domains. (Eg. premium data, government data, scientific data, social data)
• develop WCF data services that exposes any data that could be queried using jquery 

References:

• http://msdn.microsoft.com/en-us/library/cc668792.aspx
• http://blogs.msdn.com/b/astoriateam/
• http://www.odata.org/