Extensible Markup Language ( XML ) is a markup language that defines a set of rules for encoding documents in a format that is both human-...

The design goals of XML emphasize simplicity, generality, and usability over the Internet.It is a textual data format with strong support via Unicode
for the languages of the world. Although the design of XML focuses on
documents, it is widely used for the representation of arbitrary data structures, for example in web services.
Many application programming interfaces (APIs) have been developed for software developers to use to process XML data, and several schema systems exist to aid in the definition of XML-based languages.
As of 2009, hundreds of XML-based languages have been developed, including RSS, Atom, SOAP, and XHTML. XML-based formats have become the default for many office-productivity tools, including Microsoft Office (Office Open XML), OpenOffice.org and LibreOffice (OpenDocument), and Apple's iWork. XML has also been employed as the base language for communication protocols, such as XMPP.