At the end of the day this would just be saying "in XML you can also do this". Avoiding those options for people who serialise to both XML and HTML is relatively easy, just like avoiding xml:base and MathML.
Detecting stuff in non-XHTML namespaces is significantly easier than detecting incompatible use of XHTML elements.
-- Henri Sivonen [EMAIL PROTECTED] http://hsivonen.iki.fi/
