The Extensible Markup Language (XML) is an emerging standard for markup languages.  It is designed as a compromise between the simplicity of HTML and the flexibility of SGML.  It is also being referred to as generic SGML.  XML is not intended to replace HTML; rather, the two are complementary.

    The two standards emphasize different elements of document preparation; HTML handles structure and presentation of text data while XML addresses data semantics and meaning, as well as data presentation issues not addressed in a purely text-oriented language like HTML.

   The primary advantage of XML is it allows Web authors to create their own markup tags.  These tags can be as simple or as complex as the author requires.  For example, data can be marked with a tag such as <online catalog>  so they're easier to identify.  Finally, XML includes features such as bi-directional and location-independent links and transclusion, where a linked document appears as part of the current one.

For More Information:

• Flynn, Peter, et.al. The XML FAQ

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