“GData is a new protocol based on Atom 1.0 and RSS 2.0”

Google does an end run around the RSS and Atom war. GData, Google’s new API to read and write from the web, combines elements of both. It’s big additions over the Atom API are authentication and query functionality. RSS 2.0 output is mainly available for reads.

Check out the docs at Google. More on the protocol and authentication.