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Re: Namespace

From: Lachlan Hunt <lachlan.hunt@lachy.id.au>
Date: Tue, 17 Jul 2007 14:01:26 +1000
Message-ID: <469C3F16.5000801@lachy.id.au>
To: Robert Burns <rob@robburns.com>
CC: HTML WG <public-html@w3.org>

Robert Burns wrote:
> On Jul 15, 2007, at 8:49 PM, Lachlan Hunt wrote:
>> It doesn't really matter if the XHTML2 WG attempt to reuse the XHTML1 
>> namespace, they will fail if they try.  As I, and others, have 
>> explained previously, XHTML2 is fundamentally incompatible with XHTML1 
>> and simply cannot reuse its namespace without breaking compatibility.
> I believe that XHTML2 is trying to be compatible with the existing HTML 
> namespace.

That's what some in the XHTML2 WG believe also, but belief in something 
does not make it true.

> On the issue of XHTML2 incompatibility with XHTML1, some time ago you 
> listed several issues with the current XHTML2 draft:
> <http://lists.w3.org/Archives/Public/public-html/2007Jun/0700.html>
> However, this message basically just lists outstanding issues in the 
> XHTML2 draft. Not, as you suggest, insurmountable compatibility issues. 
> Nor are they serious namespace collisions.

Try reading that a little more carefully.  I listed both 
incompatibilities and outstanding issues, none of which the XHTML2 WG 
seem particularly interested in addressing.  Specifically, some of the 
incompatibilities listed include:

* <label>
* <input>
* <object src=""> vs. <object data="">
* Renaming <script> to <handler>
* etc...

>> If they do reuse the namespace, it will be impossible for a UA to 
>> support both XHTML1 and XHTML2 at the same time, and so it is both 
>> unnecessary and impossible for XHTML5 to be compatible with XHTML2 by 
>> design.
> I don't think that's right. Without namespace collisions, its hard to 
> imagine what would stop a UA from implementing both XHTML2 and XHTML1.

I think you misread what I wrote.  Sure, if they used a different 
namespace, there would be no collision and could theoretically be 
implemented together.  But I said "if they do reuse the namespace", 
where there would be collisions, it will be impossible.

> Chaals also responded to say this has already largely been accomplished 
> in Opera (with an XForms extensions).
> <http://lists.w3.org/Archives/Public/public-html/2007Jun/0778.html>

That only works in Opera because XHTML2 currently uses a different 
namespace, and some things in XHTML2 can be implemented using generic 
XML processing with CSS.  AFAIK, there has been no work on implementing 
XHTML2 in any released version of Opera.  It has just as much support as 
the hypothetical FooML would, if it were defined.

> So I'd like to remind everyone that XHTML2 is completely irrelevant 
>> and unrelated to XHTML5 and that attempting to design for 
>> compatibility between them is not a goal.
> At the same time, we may be sharing the same namespace URI.

As I said, XHTML2 *cannot* realistically reuse the the XHTML1 namespace 
because it is fundamentally incompatible.

> So I don't think its helpful at all to not address issues that could cause 
> problems for all of our constituencies: users, authors and UA developers 
> alike.

If the XHTML2 WG want to reuse the XHTML1 namespace, then they will have 
to deal with all the problems themselves.  We should not have to deal 
with the problems they create.

> The use-case that triggered this discussion was over the issue of what 
> should our recommendation say on UA conformance with regard to <img> 
> elements that have content: something that is permitted as fallback in 

We can discuss the advantages and disadvantages of that proposal and 
make a decision based on its own merits, but consistency with XHTML2 is 
not a valid reason.

> Perhaps someone from the W3C could speak to this issue, but are we to 
> assume that "XHTML2 is completely irrelevant and unrelated to XHTML5 and 
> that attempting to design for compatibility between them is not a 
> goal.", even though we may be sharing the same namespace?

Yes, because it is not our responsibility to deal with the problems 
created by the XHTML2 WG.  While I agree that it would be unfortunate if 
they shared the same namespace, it will not create any major practical 
problem in reality until some vendor attempts to support both XHTML2 and 
XHTML5 in the same implementation.  That seems unlikely and the market 
will ultimately decide upon the relevance of XHTML2.

Lachlan Hunt
Received on Tuesday, 17 July 2007 04:02:39 UTC

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