Comment by epc

GML dates to 1969, SGML from the 1970s. Internally we used something called BookMaster which kind of? looks like a precursor to HTML (you had :p. instead of <p>, :li. instead of <li>). There was an effort circa 1990-1991 (as TBL was developing HTML and HTTP) called HyTime which was an SGML application focused on hypermedia. HTML killed that fairly quickly.

See https://en.wikipedia.org/wiki/Charles_Goldfarb who shepherded GML/SGML and https://en.wikipedia.org/wiki/Standard_Generalized_Markup_La...