On this forum, XML is always discussed as a pure technology, in terms of abstract requirements like "separation".
I don't think this was XML's cause, in retrospect. I think XML is better seen as a response to (and enabler of) globalization. Its was the economics not the software engineering.
SGML was all about reducing the number of keystrokes that would be required to mark a document up: missing tags, short tags, general entities, default attributes, short references, etc. Fingers were expensive.
With globalization, the tactic of management towards costly fingers stopped being minimizing keystrokes and shifted to cheaper fingers. The economic rationale for those features disappeared, and suddenly those SGML features started to be decried as bad design, unnecessary and unnecessarily complex: and lo XML was born. People involved at that time, finding themselves in the new world, might not have been aware that they were chanelling the spirit of the age, being children of their time.
If you have a techno-centric view of XML's history, that it was caused (rather than formed) fundamentally by a desire for simplicity and purity, then the lack of a continued evolution in XML in the direction of satisfying ever more abstract loveliness must be puzzling. But if you take the economic view, however, then what is needed for a big new advance is some new international economic requirements. For example if, in the age of Snowden, business and government decided they wanted field-level encryption and security in documents, rather than just file level, that could provide the economic impetus for a new mix.
Cheers
Rick
