Extensible Markup Language (XML)

Extensible Markup Language (XML) is a simple, very flexible text format derived from SGML (ISO 8879). Originally designed to meet the challenges of large-scale electronic publishing, XML is also playing an increasingly important role in the exchange of a wide variety of data on the Web and elsewhere.

See:

• http://www.w3.org/XML/
• http://xml.coverpages.org/xml.html
• http://en.wikipedia.org/wiki/XML
• http://www.xml.org/
• What is XML? - http://www.w3schools.com/xml/xml_whatis.asp