From GML in 1969 came SGML, then in 1998 XML 1.0 was released. This was used to set out property lists in Mac OS X, and more recently have been stored in binary format.
SGML
Described as a WYSIWYG LaTeX for Mac, this app attempts to provide integrated editing of both marked-up text and rendered pages.
XML should have been the solution to so many problems: just structure documents semantically and you can rejigger them any way that you want. But there is more to it than that…
The Eclectic Light Company 