The original plan:
- XML (a lightweight SGML) 1998
- generic markup
- validation
- XLink / XPointer (lightweight HyTime) 2002
- stand-off links
- n-way linking
- structure-based addressing
- XSL (lightweight DSSSL) 1999, 2001
- structure-based formatting and rendering
- tree transformations
- flow objects
- XML applications / XML-based languages (SMIL, XHTML, MathML, ...)
An early addition: XML Namespaces 1.0.