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Extensible Mark-up Language.

XML is a specification developed by the W3C and is a mark-up language for structured documents. XML had its roots in specifying and formatting for web documents and web pages, providing a natural development beyond HTML, but it is now also frequently used to provide a common means of data exchange. It supports communication between various companies and applications and is a simplified version of SGML. Despite the various operating system platforms and end devices, data access logic and application logic do not have to be changed.

An XML file is a file that is readable using a standard text editor. The file uses tags to indicate the start and end of blocks, with each opening tag having a matching closing tag (although there are exceptions). Since each tag can contain other tags, XML files provide a means of providing a hierarchy of data. Since each tag has a corresponding closing tag it is possible to read an XML file without understanding what each of the tags means, which is why it is possible to build generic XML parsers.

See also DTD, JSON and the file extensions .xml and .xsd. Whilst XML files typically have a .xml file extension, they do not have to and many other file extensions are used for specific applications.

For more information see: