W3C home > Mailing lists > Public > public-xhtml2@w3.org > February 2009

Re: [Fwd: Using XMLNS in link/@rel]

From: Mark Nottingham <mnot@mnot.net>
Date: Fri, 27 Feb 2009 21:54:24 +1100
Cc: www-tag@w3.org, "Dan Brickley" <danbri@danbri.org>, "Ben Adida" <ben@adida.net>, RDFa <public-rdf-in-xhtml-tf@w3.org>, "XHTML WG" <public-xhtml2@w3.org>
Message-Id: <98EE693C-B02B-4E12-A505-2D16A22C1145@mnot.net>
To: Steven Pemberton <steven.pemberton@cwi.nl>

Hello Steven,

On 27/02/2009, at 9:06 PM, Steven Pemberton wrote:

> On Fri, 27 Feb 2009 10:31:57 +0100, "Mark Nottingham"  
> <mnot@mnot.net> said:
>> Creative Commons just released a new spec:
>>   http://wiki.creativecommons.org/Ccplus
>> that has markup in this form:
>>   <a xmlns:cc="http://creativecommons.org/ns#"
>> rel="cc:morePermissions" href="#agreement">below</a>
>> (in HTML4, one assumes, since they don't specify XHTML, and this is
>> what the vast majority of users will presume).
>
> In the link you refer to they don't specify either, but I imagine  
> they mean XHTML,

I will wager any amount of money you care to name that more than 99%  
of the document's readers (as it stands) will assume HTML4.


> and I'm sure Ben Adida of CC can speak up here.
>
>> However, it appears that they adopted this practice from RDFa;
>>   http://www.w3.org/TR/rdfa-syntax/#relValues
>> which, in turn, *does* rely upon XHTML. However, XHTML does *not*
>> specify the @rel value as a QName (or CURIE, as RDFa assumes);
>> http://www.w3.org/TR/2008/REC-xhtml-modularization-20081008/abstraction.html#dt_LinkTypes
>> "Note that in a future version of this specification, the Working
>> Group expects to evolve this type from a simple name to a Qualified
>> Name (QName)."
>>
>> So, that's an expectation, not a current specification.
>
> In fact it is a current specification. RDFa specifies a version of  
> XHTML that defines the meaning of CURIEs in rel and rev values. Note  
> that this is also not invalid HTML4 (which also allows such values  
> in a rel - they are CDATA - but doesn't specify what they mean).

   http://www.w3.org/TR/rdfa-syntax/
refers to
   http://www.w3.org/TR/2001/REC-xhtml11-20010531/
which contains
   http://www.w3.org/TR/2001/REC-xhtml11-20010531/doctype.html
which refers to, for the Hypertext module (note 'latest version' URI):
   http://www.w3.org/TR/xhtml-modularization/abstract_modules.html#s_hypertextmodule
which leads back to
   http://www.w3.org/TR/xhtml-modularization/abstraction.html#dt_LinkTypes
i.e., the same, albeit most recent (instead of versioned) URI for
   http://www.w3.org/TR/2008/REC-xhtml-modularization-20081008/abstraction.html#dt_LinkTypes

Even taking the other road and going with the contemporary version,
   http://www.w3.org/TR/2001/REC-xhtml-modularization-20010410/abstraction.html#dt_LinkTypes
it's still just short names, with no reference to CURIEs or QNames at  
all.

What am I missing?

The only place I see this defined is in the RDFa syntax document  
itself -- do you mean that is the specification of authority? I note  
that it specifies /html/@version="XHTML+RDFa 1.0", and it has its own  
DTD, so in a way I suppose it's not really an extension to XHTML, but  
a re-definition of it...


>> Of course, this conflicts with the Link draft;
>>  http://tools.ietf.org/id/draft-nottingham-http-link-header-04.txt
>> which we've worked pretty hard to come to consensus on across a broad
>> selection of communities (Atom, POWDER, OAuth, HTTP, and
>> optimistically, HTML5).
>>
>> A few observations and questions;
>>
>> 1) I'm more than happy to specify in the Link that in XHTML, a link
>> rel value is indeed a QName, if XHTML chooses to take that position
>> (although I believe a URI is a better fit than a QName here, as in
>> most other places). Can we get a current reading from the XHTML world
>> on this?
>
> A CURIE is a URI not a QName, so you're OK.

I haven't paid a lot of attention to them to date, but as far as I can  
see, a CURIE is most definitely not a URI; at most, it's a shorthand  
for one.


> CCing the XHTML2 WG and/or RDFa group would have helped in this case  
> if you wanted a response from them :-)

I wanted to get a feel from an architectural standpoint before talking  
to WGs about potentially irrelevant problems, but point taken.


>> 2) However, it seems like RDFa is jumping the gun by assuming @rel is
>> a CURIE right now.
>
> See above. It is already a Rec.
>
> [All the rest snipped since it was based on the assumption that XHTML 
> +RDFa isn't a Rec].

As I said before, the third point is IME the most concerning. Having  
two subtly incompatible syntax for the same attribute in HTML and  
XHTML isn't a great situation, but assuming that one is valid to use  
in the other is far more troublesome.

Cheers,

--
Mark Nottingham     http://www.mnot.net/
Received on Friday, 27 February 2009 10:55:11 GMT

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