Chapter 18. Resource Description Framework and Channel Definition Format

This chapter is about two XML applications that work with metadata. Metadata is data that describes data, and the applications I'm going to take a look at are Resource Description Framework (RDF) and Channel Definition Format (CDF).

As you can gather from its name, RDF is a language that lets you describe resources. Although it's typically used to describe Web documents and sites, you can also use it to describe CD collections, books in a library, a collection of antique pen knives, and more. It's a general-purpose XML application that is helping to standardize the way people handle data on the Internet. Some consistent way of working with vast amounts of data on the Internet is sorely needed, and RDF is one possible solution. You may recall our discussion of canonical XML, which puts XML documents into a format that may easily be compared—RDF is actually stored in documents separate from the resources it describes, and it provides a standard description language.

CDF is similar, but more targeted. It's a language supported by only Internet Explorer, and it's designed to let you create channels in that browser to provide easy access to Web documents and sites to users. Creating a channel means letting Internet Explorer know all about what documents you want the user to be able to access and when—even providing for scheduled automatic download of entire Web sites or software updates. Using channels, the user needs only to click an icon to download the documents referenced by the CDF that created the channel.

I'll start with RDF, taking a look at that XML application in overview.