Text files used for creating Active Channels, Active Desktop items, and channel screen savers for managed webcasting of content to user's desktops. CDF files are based on the Channel Definition Format (CDF) standard. CDF files provide a mechanism for allowing users to select the content they want to download from a Web site, and they let administrators schedule content for delivery to user's desktops.
CDF files are used to convert existing Web sites into Active Channels without the need to change the existing site in any way. You simply create a CDF file using a text editor such as Microsoft Notepad and include it in your site. This will allow the content of the site to be webcast to user's browsers. The CDF file must be saved with the extension .cdf, and a link on your site should point to this file so that users can subscribe to the channel.
A typical CDF file defines a channel hierarchy for the different Web sites making up the Active Channel. This channel hierarchy contains a table of contents for webcasting the content and consists of a top-level channel, subchannels, and actual content items (Web pages). The simplest format for a CDF file is a list of Uniform Resource Locators (URLs) that point to specific Web pages in the site. More advanced CDF files can contain information such as
The syntax of advanced CDF file items is based on the Extensible Markup Language (XML), an open specification that provides extensibility to standard Hypertext Markup Language (HTML) files. More than one CDF file can be created for a site, allowing users to subscribe to information in different fashions. For example, a news site can have separate CDF files for news, sports, and weather subscriptions.
For specific information on the syntax of CDF files and how to create them, refer to the Microsoft Internet Client SDK.
Channels in Active Channel enable personalized delivery of Web content using Web applications designed for Internet Information Server (IIS) for Windows NT (Internet Information Services for Windows 2000). Active Server Pages (ASP) can be used for dynamically generating personalized CDF files for users. Cookies can also be used for dynamically generating customized CDF files for users. These CDF files can be customized on the basis of preferences that a user specifies on an HTML form prior to subscribing to the channel.