XML?Defining Documents on the 'Net

Catalog printers, pay close attention: XML—an enhancement of HTML or a redefined, simplified version of SGML, depending on how you view it—is one document manipulation language you need to know, and know well.

XML will be your friend. Why?

Extensible Markup Language (XML) allows users to define their own structure and tags, completely tailored to a particular document. XML is considered a subset of Standard Generalized Markup Language (SGML)—the 20-year-old, far too complex, yet far too vital to lose an ounce of respect for—document language.