An Acronym (yet another TLA) for eXtensible Markup Language, a marginally human read-/editable MarkupLanguage which is a simplified decendant of SGML.

SGML was an extremely comprehensive standard for which hardly a single fully compliant parser was ever written. Many of its features, even implemented ones, are hardly used. On the other hand, it lacks various useful features. XML was designed to address these shortcomings while reducing the language specification to a small set of rules in order to be easily and consistently parsable. It lacks features such as CONCUR but adds others such as NameSpaces (as good an idea in a MarkupLanguage as they are in a ProgrammingLanguage).

XML uses a DTD or a Schema to describe the structure of data within a XML document. It is often manipulated using a langauge called XSLT, which is a FunctionalLanguage? written in XML syntax.

Good websites full of useful XML stuff include:

1. O'Reilly's: http://www.xml.com/
2. The official W3C website: http://www.w3.org/
3. The XML FAQ: http://www.ucc.ie/xml/
4. Apache XML Project: http://xml.apache.org/

See also:

Valid, WellFormed, XHTML and HTML.

This pages regularly re-written by StuartYeates.

AsSeenOnSlashdot

XML is like:

• SGML without configurability
• HTML without forgivingness
• LISP without functions
• CSV without flatness
• PDF without Acrobat
• ASN.1 without binary encodings
• EDI without commercial semantics
• RTF without word-processing semantics
• CORBA without tight coupling
• ZIP without compression or packaging
• FLASH without the multimedia
• A database without a RDBMS or DDL or DML or SQL or a formal model
• A MIME header which does not evaporate
• Morse code with more characters
• Unicode with more control characters
• A mean spoilsport, depriving programmers the fun of inventing their own syntaxes during work hours
• The first step in Mao's journey of a thousand miles
• The intersection of James Clark and Oracle
• The common ground between Simon St. L and Henry Thomson
• The secret love child of Uche and Elliotte
• Microsoft's secret weapon against Sun?'s Open Office
• Sun's secret weapon against Microsoft's Office
• The town bicycle

--Rick Jelliffe