The Standard Generalized Markup Language (SGML; ISO 8879:1986) is a standard for defining generalized markup languages for documents. ISO 8879 Annex A.1 states that generalized markup is "based on two postulates": Declarative: Markup should describe a document's structure and other attributes rather than specify the processing that needs to be performed, because it is less likely to conflict with future developments. Rigorous: In order to allow markup to take advantage of the techniques available for processing, markup should rigorously define objects like programs and databases. DocBook SGML and LinuxDoc are examples which used SGML tools. Standard versions SGML is an ISO standard: "ISO 8879:1986 Information processing – Text and office systems – Standard Generalized Markup Language (SGML)", of which there are three versions: Original SGML, which was accepted in October 1986, followed by a minor Technical Corrigendum. SGML (ENR), in 1996, resulted from a Technical Corrigendum to add extended naming rules allowing arbitrary-language and -script markup. SGML (ENR+WWW or WebSGML), in 1998, resulted from a Technical Corrigendum to better support XML and WWW requirements. SGML is part of a trio of enabling ISO standards for electronic documents developed by ISO/IEC JTC 1/SC 34 (ISO/IEC Joint Technical Committee 1, Subcommittee 34 – Document description and processing languages) : SGML (ISO 8879) – Generalized markup language SGML was reworked in 1998 into XML, a successful profile of SGML. Full SGML is rarely found or used in new projects. DSSSL (ISO/IEC 10179) – Document processing and styling language based on Scheme. DSSSL was reworked into W3C XSLT and XSL-FO which use an XML syntax. Nowadays, DSSSL is rarely used in new projects apart from Linux documentation. HyTime – Generalized hypertext and scheduling. HyTime was partially reworked into W3C XLink. HyTime is rarely used in new projects. SGML is supported by various technical reports, in particular ISO/IEC TR 9573 – Information processing – SGML support facilities – Techniques for using SGML Part 13: Public entity sets for mathematics and science In 2007, the W3C MathML working group agreed to assume the maintenance of these entity sets. History SGML descended from IBM's Generalized Markup Language (GML), which Charles Goldfarb, Edward Mosher, and Raymond Lorie developed in the 1960s. Goldfarb, editor of the international standard, coined the "GML" term using their surname initials. Goldfarb also wrote the definitive work on SGML syntax in "The SGML Handbook". The syntax of SGML is closer to the COCOA format.