[twoodfin]

This isn’t surprising: XML’s core purpose was to simplify SGML for a wider breadth of applications on the web.

HTML also descended from SGML, and it’s hard to imagine a more deeply grooved structure in these models, given their training data.

So if you want to annotate text with semantics in a way models will understand…

[tingletech]

XML and HTML are SGMLs

[ChrisSD]

HTML diverged from SGML pretty early on. Various standards over the years have attempted to specify it as an application of SGML but in practice almost nobody properly conformed to those standards. HTML5 gave up the pretence entirely.