Re: xmlns in HTML5

On 16/7/09 11:20, Ian Hickson wrote:
> On Thu, 16 Jul 2009, Toby Inkster wrote:
>> Ian Hickson wrote:
>>
>>> Authors must not use elements, attributes, and attribute values that
>>> are not permitted by this specification or other applicable
>>> specifications.
>>>   -- http://www.whatwg.org/specs/web-apps/current-work/#semantics-0
>> Which "other specifications" are "applicable"?
>
> Pretty much any that claim to be and that the people affected agree are
> applicable. If an RDFa specification said that text/html could have
> arbitrary xmlns:* attributes, then the HTML5 specification would (by
> virtue of the above-quoted sentence) defer to it and thus it would be
> allowed. Similarly, Microsoft could write a spec and claim<marquee>  is
> valid, as well as<msword>  and<excel>.
>
> Of course, if a community doesn't acknowledge the authority of such a
> spec, and they _do_ acknowledge the authority of the HTML5 spec, then it
> would be (for them) as if that spec didn't exist. Similarly, there might
> be a community that only acknowledges the HTML4 spec and doesn't consider
> HTML5 to be relevant, in which case for them, HTML5 isn't relevant.
>
> This is how specs work. :-)

How would you expect a validator for such a flexible format to work?

I just tried validator.nu HTML5 (experimental) on a document with 
xmlns:*, and got "Error: Attribute xmlns:foaf not allowed here."

Should these errors be demoted to warnings? Or each community makes it's 
own validator?

Dan