eXtensible Markup Language is a type of markup language used for encoding documents in machine-readable form.
The main XML design goals emphasize simplicity, generality, and usability over the Internet. It is a textual data format, with strong support via Unicode for all the other languages in the world.
Software developers may access XML data by using the many programming interfaces available to them, and several schema systems designed 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 most office-productivity tools, including Microsoft Office, which uses its Office Open XML, OpenOffice.org, which uses OpenDocument, and Apple's iWork.