Channel Definition Format (CDF) is a file format based on Extensible Markup Language(XML) that can be used to subscribe to services and content on the Web and send the selected information to interested parties.
In the CDF format, the web servers collect the websites and work in a broadcast manner by distributing the services and content to the appropriate clients. On the server side, the CDF format allows the web publisher to offer automatically updated information through individual channels. On the client side, the Channel Definition Format indexes the content for the channel to which the user subscribes. The CDF format defines the tags used to describe a web channel.