SGML (Standard Generalized Markup Language)

It was adopted in 1986 as an international standard (ISO 8879) for the creation, management, storage, and delivery of information products. HTML and its possible successor, XML, are both subsets of SGML. See also the Wikipedia Entry.

Useful Links

 * http://xml.coverpages.org/sgml.html
 * http://www.oasis-open.org/cover/burnardw25-index.html
 * http://www.oasis-open.org/cover/sgmlhist0.html