The e*X*tensible *M*arkup *L*anguage is a format for document and data representation. It is a meta-language that allows the definition of markup languages. XML is not a markup language itself. It is a (simplified) subset of *SGML* (Standard Generalized Markup Language). Initially designed for use on the web, but now its use extends to many more areas. It is being used also for protocol descriptions, remote procedure calls, etc. New markup languages are called "XML Applications", which can be confusing sometimes A short list of XML applications: WDDX, XML-RPC, SOAP, XML Schema, CML, RSS, XHTML, MathML, SVG, DocBook XML.