XML is derived from SGML, which evolved from GML, developed in 1971 by Charles Goldfarb of IBM, and was one of the world’s first ‘generic’ or ‘generalized’ markup languages, along with Tunnicliffe’s GenCode. Generalized markup is supposed to separate the form of a document from its presentation, although in practice this is only possible to a limited degree (Raymond et al., 1992, p. 16).

GML didn’t completely die out with the advent of SGML and later XML; in fact a version of it lived on under a different name: as the most widely used form of digital text on the planet: HTML.