HTML is not XML.
You *can* have XHTML that is XML-compatible, though.
But there are many rules in XML that are not necessarily followed in HTML.
If you use XHTML in strict mode and validate it (say with the w3c validator) *then* you can probably treat it as XML for the purposes of this usage.
An optimist sees the glass as half full.
A pessimist sees the glass as half empty.
A realist drinks it no matter how much there is.