W3C Technologies and Accessibility - slide "Extensible Markup Language (XML) family"

Design formats with XML 1.0: Well-formedness.
Examples: XHTML, MathML, SVG (demos), SMIL (demo), SMIL Animation
Constrain and validate with DTDs (XML 1.0) and XML Schema (Structures and Data Types)
Mix elements with XML Namespaces: avoid name conflicts
Link with XLink, XPointer, XBase
Compose/Decompose with XInclude, XML Fragment