Disagree. HTML, until HTML 4.01 published 1999, was formulated as an SGML vocabulary. Then, starting in 1997, W3C (technically, the SGML Extended Review Board i

Disagree. HTML, until HTML 4.01 published 1999, was formulated as an SGML vocabulary. Then, starting in 1997, W3C (technically, the SGML Extended Review Board in cooperation with ISO) "went meta" and created XML as an SGML subset in anticipation of a wealth of new vocabularies on browsers to be supported, of which SVG and MathML made it. Today, these vocabularies are integrated into HTML, with HTML rather than XML parsing rules (for example, element names are treated case-insensitive). HTML itself still uses tag inference and attribute shortforms that are only part of SGML but not the XML subset of SGML. Basically, the multi-year detour of creating XML was not worth it for the web since everything XML could do was by definition possible using SGML as well, it being a strict superset of XML, despite XML being hugely successful in enterprise computing and the publishing industry, and most HNers only knowing XML. What XML (XHTML2) was onto, however, was a completely unrealistic attempt to redefine browser behavior and vocabulary, with no buy-in from browser vendors (except Opera?), and with things such as XForms and wildly unproven RDF/SPARQL stuff. Ian Hickson was right in 2004 to fork HTML; browser vendors had no alternative.