XML

XML (short for the Extensible Markup Language) is a general specification for the creation of custom markup languages with their own elements, hence an "extensible language". The XML format facilitates the structured storage and retrieval of data from multiple locations and sources.

Several popular implementations of XML exist, including:
 * XHTML, a more strict version of HTML currently adopted in web standards
 * RSS, a popular web feed format
 * Scalable Vector Graphics (SVG), a standardized vector graphics file format.