RE: The X in HTML

> From: Johannes Koch [mailto:koch@pixelpark.com] 
> 
> You can write well-formed X(HT)ML documents without any DTD. Just mix 
> XHTML elements with your additional ones (using another 
> namespace). But 
> you cannot expect the documents to be valid.

There are two ways towards XHTML Modularization. One is DTDs and the
other is though XML Schema. I find the second easier to merge with my
work. You can find extensible schemas and the relative draft at [1].
Even features a convenient .zip for download.

[1] http://www.w3.org/TR/xhtml-m12n-schema/

Cheers,

Manos