The Google Data API is a mix of simple query language, based on OpenSearch, using Atom and RSS to represent the Data, and an updating prototcol based on the Atom Publishing protocol (IETF draft). The release of the Google Calendar was well received, and since that initial release beginning of 2006, Blogger, Google CodeSearch, Google Base and Google Spreadsheets have joined.
The API has an active developer community at code.google.com, and due to the freely available documentation and open licencing scheme, was already implemented outside of Google in several languages. The API received kind reviews from our competition, and will be a building block used in and outside of Google for advanced data mashup applications.
A former long time Microsoft employee, Frank Mantek joined Google in 2005 to work on the Google Data API. His past work include SQLXML, Internet Explorer, and other Microsoft technologies. When he is not working on new data technologies, he enjoyes playing the Djembe really loud.