Atom: Data Access Over the Web

Atom is a data format and protocol, commonly used for Web content syndication and blogging, that enables data access over the Web. An Atom-capable Web site includes one or more feeds (formally called “collections”), which are URL-accessible lists of data items called entries. The Atom specification defines the following technologies for such sites:

• An XML-based format for feeds and entries, and a “service document” format for determining which feeds are available at a site
• A publishing protocol for creating, reading, updating, and deleting entries using Hypertext Transfer Protocol (HTTP), the standard Web protocol.

Both the format and the publishing protocol are maintained by the Internet Engineering Task Force, the organization that also manages the TCP/IP Internet protocols.

Atom’s most prominent use today is in blogging, where it serves as an alternative to the Really Simple Syndication (RSS) format for feeds that deliver sequences of articles and reader comments. However, the Atom formats are extensible, and vendors such as Google and Microsoft have used them to give Web applications access to calendars, contacts, photos, and other types of data stored in online services. Atom has some technical advantages for these types of applications: