On pages 150-151 of "IBM's 360 and Early 370 Systems" with its endnote 85 on page 701 there is documentation of James W. Franklin's text processing program "developed for the purpose of incorporating, within hours, revisions into the thick, highly technical architecture manual." Jim, a technical editor by profession, used simple markup tags styled on an editor's way of marking up a document. This lead by stages to GML. In my experience with IBM's early implementations, these primitive tags were used to define markup macros that evolved into SGML. I find Word's wysiwig approach more useful for simple documents but Word Perfect's markup with Reveal Codes more like my experience using GML to create large documents.