[whatwg] Re: DOCTYPE shouldn't be optional

Ian Hickson ian at hixie.ch
Fri Jul 9 06:51:44 PDT 2004

On Wed, 7 Jul 2004, Malcolm Rowe wrote:
> I really don't know enough about the issue that the TAG are discussing
> to comment, though I think it essentially boils down to how you can
> determine if a document is 'valid' if it contains elements from multiple
> namespaces.  There's no generic way to validate a compound document, for
> example.

I'm not convinced of the need for validity checking (beyond syntax
checking) for reasons I mentioned the other day, but if one assumes that
one wants validity checking of compound documents, it's not hard: you just
need a schema language that supports describing constraints in terms of
mixed namespaces. For example, "<ul> can only contain <li>" or "<div> can
contain anything" or "<svg:rect> is only allowed inside <svg:svg>" or
"<svg:svg> is allowed anywhere". Then you take all the constraints and see
if all the elements in the document obey all of them.

Not that anyone has actually written such a language, as far as I know.

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

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