XML

Extensible Markup Language (XML) is a markup language that defines a set of rules for encoding documents in a format that is both human-readable and machine-readable. The W3C's XML 1.0 Specification^[2] and several other related specifications^[3]—all of them free open standards—define XML

The design goals of XML emphasize simplicity, generality, and usability across the Internet.^[5] It is a textual data format with strong support via Unicode for different human languages. Although the design of XML focuses on documents, the language is widely used for the representation of arbitrary data structures^[6] such as those used in web services.

Several schema systems exist to aid in the definition of XML-based languages, while programmers have developed many application programming interfaces (APIs) to aid the processing of XML data.

APPLICATIONS

The essence of why extensible markup languages are necessary is explained at Markup language (for example, see Markup language § XML) and at Standard Generalized Markup Language.

Hundreds of document formats using XML syntax have been developed,^[7] including RSS, Atom, SOAP, SVG, 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^{[citation needed]}. XML has also provided the base language for communication protocolssuch as XMPP. Applications for the Microsoft.NET Framework use XML files for configuration, and property lists are an implementation of configuration storage built on XML.^[8]

Many industry data standards, e.g. HL7, OTA, FpML, MISMO, NIEM, etc. are based on XML and the rich features of the XML schema specification. Many of these standards are quite complex and it is not uncommon for a specification to comprise several thousand pages.