Moving Forward I

The XHTML approach

Recasting HTML as XML XHTML, the Extensible Hypertext Markup Language, is moving HTML to a stricter XML syntax and supplementing it with tools like XML namespaces, opening the possibility of XHTML document containers hosting multiple vocabularies.
Formally provides HTML structures to XML tools XHTML provides a framework in which developers who want to transmit XML can support that work with the HTML vocabulary, easing co-existence with legacy browsers.
Slow-moving, somewhat limited XHTML 1.0 makes it possible to mix XML and HTML, but it only provides the foundation. XHTML 1.1 brings modularization tools, but so far they seem complex and unwieldy. This approach may limit the number of people able to add modules to XHTML, though browser implementation may have a similar effect.
Great for W3C efforts XHTML modules seem like a good fit for W3C efforts like MathML, SMIL, and SVG, which may become part of a more comprehensive browser platform.