[dragonwriter]

XSL (Extensible Stylesheet Language) the stylesheet part, it included XSLT (transform), XPath, and XSL-FO (XSL Format Objects).

XSLT and XPath each went on to great solo careers, XSL-FO kind of fizzled when XML+XSL failed to displace HTML+CSS.

[spiralx]

XSL:FO is great for turning into PDFs though.

There's also XQuery for transformations and XSD/RelaxNG for schemas, the whole combination of XML database, WYSIWYG (via XSLT) XML editor and output transformations is very powerful, every journal we published and every site we ran at the British Medical Journal was generated that way.