An introduction to the family of Google Data APIs. The Google Data API Protocol provides a REST-inspired system for reading, writing, and modifying information on the web. Many services at Google provide a Google Data API, including YouTube, Blogger, Picasa Web Albums, Google Calendar, and Google Analytics. The protocol currently supports two primary modes for information representation and access: Atom/AtomPub and JSON. Google also provides client libraries for easy programmability in Java, JavaScript, .NET, Python, PHP, and Objective-C. http://code.google.com/apis/gdata