[html5] XHTML extending. id, class, style attributes support for other namespaces

Ian Hickson ian at hixie.ch
Thu Oct 18 15:42:56 PDT 2012

On Fri, 19 Oct 2012, Anton Vitr wrote:
> Thank you Ian!
> > It sounds like the simplest way to achieve what you want to do is 
> > invent a new language that's a superset of HTML. So your documents 
> > wouldn't have to be HTML-compliant. Simplest way to do this is 
> > probably just to use your own namespace in XML.
> Did you mean XML, and not XHML?

XHTML isn't really a thing. It's just shorthand for "using elements in the 
HTML namespace in XML".

> > Such documents wouldn't be conforming HTML, and wouldn't work if your 
> > library wasn't available for whatever reason.
> Google return me a lot results for "XHTML extending", including spec - 
> http://www.w3.org/TR/1999/xhtml-modularization-19990406/extending.html 
> But, XHTML is too strict and do not widely used.
> Is there any plans to include some king of extending in HTML5 (not 
> XHTML)? Or my case(problem) is very rare, and is no point to encourage 
> people to extent HTML language?

The spec has a section about this:


But IMHO you'd not be extending XHTML, you'd be making your own language 
that happens to embed parts of XHTML.

Ian Hickson               U+1047E                )\._.,--....,'``.    fL
http://ln.hixie.ch/       U+263A                /,   _.. \   _\  ;`._ ,.
Things that are impossible just take longer.   `._.-(,_..'--(,_..'`-.;.'

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