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Re: xmlns in HTML5 (was: Telecon Agenda- Thursday 1500 UTC)

From: Ian Hickson <ian@hixie.ch>
Date: Fri, 17 Jul 2009 11:23:02 +0000 (UTC)
To: Steven Pemberton <Steven.Pemberton@cwi.nl>
Cc: Toby Inkster <tai@g5n.co.uk>, Manu Sporny <msporny@digitalbazaar.com>, RDFa <public-rdf-in-xhtml-tf@w3.org>
Message-ID: <Pine.LNX.4.62.0907171115550.12284@hixie.dreamhostps.com>
On Fri, 17 Jul 2009, Steven Pemberton wrote:
> On Fri, 17 Jul 2009 00:29:42 +0200, Ian Hickson <ian@hixie.ch> wrote:
> > On Thu, 16 Jul 2009, Steven Pemberton wrote:
> > > On Thu, 16 Jul 2009 10:50:52 +0200, Toby Inkster <tai@g5n.co.uk> wrote:
> > > >
> > > > For the same reason, xmlns:foo attributes aren't allowed in HTML4 
> > > > either.
> > > 
> > > Actually, to allow for future changes, the spec says: [...]
> >
> > So the following is valid HTML4?
> 
> Not valid, but permitted.

Woah. What's the difference between "valid" and "permitted"? Aren't they 
both synonyms of "conforming"?


> > > "If a user agent encounters an attribute it does not recognize, it 
> > > should ignore the entire attribute specification (i.e., the 
> > > attribute and its value)." 
> > > http://www.w3.org/TR/html401/appendix/notes.html#notes-invalid-docs
> > > 
> > > In other words, it should act as if it weren't there. So it is 
> > > allowed, but no meaning is defined.
> > 
> > (I disagree with your interpretation of that text, by the way; it is a 
> > statement about user agents, not a statement about the conformance of 
> > HTML documents themselves. Requirements on user agents are not the 
> > same as requirements on documents.)
> 
> I agree entirely. In fact one of my main problems with the HTML5 spec is 
> that it seems to conflate the two, but considering your statement above, 
> the problem must just be that it entwines the two.

Requirements in HTML5 are organised by topic, not by conformance class, if 
that's what you mean, yes. This is generally speaking a pretty common way 
of writing specs at the W3C (e.g. it's what CSS, SVG, and XML all do).

(If you have any feedback on the HTML5 spec, please send it to 
public-html; any feedback would be very welcome.)


> But the HTML4 spec defines a document type, and says the processor for 
> that document type must accept certain deviations from that in order to 
> allow for future change. In other words the spec anticipated that other 
> document types would be sent in the future.

Sure, future compatibility is a pretty standard part of any language. But 
if you agree that the above quote is a statement about _user agents_, as 
opposed to authors, I don't understand how you then conclude that it can 
in any way affect document conformance (what authors are permitted to do).

-- 
Ian Hickson               U+1047E                )\._.,--....,'``.    fL
http://ln.hixie.ch/       U+263A                /,   _.. \   _\  ;`._ ,.
Things that are impossible just take longer.   `._.-(,_..'--(,_..'`-.;.'
Received on Friday, 17 July 2009 11:23:42 GMT

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