Google Data API and GData

Since 2006, google collects API programming interfaces in the Google Data (gdata) project. At their website, you find links to google docs, calendar, spreadsheet, youtube, and more.

It is a one-stop place to find interfaces for the various google services. For Semantic Web developers, it is also a good overview how google shapes its interfaces to its web-based applications. Get inspired by the pros.

Especially the GData protocol and data format is worth a look. It’s a generic API for getting and querying data, based on RSS 2.0 and Atom.
In the GData reference, you find a description of the Atom extensions and a simple query-format extending it.

Assuming a feed is hosted at the URI, then elements within the feed can be queried with the following URI:

A kind of “easy going sparql”.

In their own words:
The Google data APIs provide a simple standard protocol for reading and writing data on the web.

These APIs use either of two standard XML-based syndication formats: Atom or RSS. They also have a feed-publishing system that consists of the Atom publishing protocol plus some extensions (using Atom’s standard extension model) for handling queries.

Many Google services support the Google data API protocol.