The Open Data Protocol (OData) is an open web protocol for querying and updating data. The protocol allows for a consumer to query a datasource over the HTTP protocol and get the result back in formats like Atom, JSON or plain XML, including pagination, ordering or filtering of the data.
Many of the building blocks that make up OData are standardized via Atom and AtomPub. The OData specification is available under the Microsoft Open Specification Promise (OSP). Microsoft has released an OData software development kit (SDK) consisting of libraries for .NET, PHP, Java, JavaScript, webOS, and the iPhone.