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Learning XML, 2nd Edition by Erik T. Ray

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Documents Describing Documents

Many XML documents contain metadata, information about themselves that help search engines to categorize them. But not everyone takes advantage of the possibilities of metadata. And, unless you’re using an exhaustive program that spiders through an entire document collection, it’s difficult to summarize the set and choose a particular article from it. Making matters worse, not all documents have the capability to describe themselves, such as sound and graphics files. To address these problems, a class of documents evolved that specialize in describing other documents.

To fully describe different kinds of documents, these markup languages have some interesting features in common. They list the time documents have been updated using standard time formats. They label the content type, be it text, image, sound, or something else. They may contain text descriptions for a user to peruse. For international documents, they may track the language encodings. Also interesting is the way documents are uniquely identified: using a physical address or some nonphysical identifier.

Describing Media

Rich Site Summary (or Really Simple Syndication, depending on whom you talk to) was created by Netscape Corp. to describe content on web sites. They wanted to make a portal that was customizable, allowing readers to subscribe to particular subject areas or channels . Each time they returned to the site, they would see updates on their favorite topics, saving them the trouble ...

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