[whatwg] Re: DOCTYPE shouldn't be optional

[Ian Hickson]

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.

-- 
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