OData is a new API protocol that has recently been released by Microsoft, along with the launch of their new site on the 16th March 2010. It is a RESTful standard, which adds a lot of its own goods to the table.

As a RESTful standard, it exposes a web service in the form of resources accessible via discrete HTTP urls, representing actions via the HTTP methods. It fills in the gaps that the REST style of architecture leaves open, giving a full specification, from the request to the response (although omitting authentication and authorisation). OData surprisingly also allows RPC-style operations as well.

First up, there is no silver bullet in building a web service infrastructure. There are two prevailant types, however, that you should ideally be choosing from:

• RPC (remote procedure call) – e.g. SOAP, XML-RPC
• REST (Representational state transfer) – e.g. umm? REST?

What I strongly suggest is using one of these, and not designing your own protocol, or proprietry XML straight-up. As for which you should choose…