Extensible Markup Language (XML) is a simple, very flexible text format derived from SGML (ISO 8879). XML is a simplified subset of SGML. It was originally designed to meet the challenges of large-scale electronic publishing, and he improves the functionality of the Web by letting you identify your information in a more accurate, flexible, and adaptable way. XML contrasts with HTML, which has an inflexible, single-purpose vocabulary of elements and attributes that, in general, cannot be repurposed. With XML, it is much easier to write software that accesses the document's information, since the data structures are expressed in a formal, relatively simple way.

This article presents the increasingly important role of XML in the exchange of a wide variety of data on the Web and elsewhere.