Some dates:
1967: early work on generic markup: logical markup, not appearance- or process-oriented
1973: Generalized Markup Language
1986: Standard Generalized Markup Language (SGML) an ISO standard
1996: Work on ‘SGML on the Web’ starts in W3C
  • Make SGML Web-ready. Keep XML SGML-compatible.
  • Keep the power: nested structure, world view, reusability, generic markup, data ownership.
  • Lose the cruft: simplify, simplify!
1998: XML 1.0 becomes a W3C Recommendation
2003: over 20 XML-related specs at W3C — why so many?