Descriptive mark-up consists of codes that describe the logical structure and semantics of a document, usually in a way which can be interpreted by many different software applications. The two main open standards for descriptive mark-up are SGML (Standard Generalized Markup Language), published as a Standard by the International Standards Organization (ISO) in 1986, and XML (Extensible Markup Language), which was published as a Recommendation of the World Wide Web Consortium (W3C) in 1998.
