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Using XMLNS in link/@rel

From: Mark Nottingham <mnot@mnot.net>
Date: Fri, 27 Feb 2009 18:15:45 +1100
Message-Id: <64A6A88B-2DFF-4B8F-901F-7E246E404443@mnot.net>
To: "www-tag@w3.org WG" <www-tag@w3.org>
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).

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.

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?

2) However, it seems like RDFa is jumping the gun by assuming @rel is  
a CURIE right now. This is not promoting interoperablity or shared  
architecture, because no XHTML processor that isn't aware of RDFa can  
properly identify these link relations. My preference would be an  
erratum to RDFa removing this syntax, replacing them with a self- 
contained identifier (i.e. a URI). Thoughts?

3) CC's adoption of *proposed* XHTML conventions from RDFa into HTML4  
via CURIEs further muddies the waters; xmlns has no meaning whatsoever  
in HTML4, so they're promoting bad practice there by circumventing the  
specified Profile mechanism. I find this aspect of this the most  
concerning, and it needs clarification (more colourful words come to  
mind, but I'll leave it there for now).

Thanks,

P.S., I realise that this involves at least three additional  
communities, but the TAG seems like the logical place for the initial  
discussion and eventual coordination of this issue.

--
Mark Nottingham     http://www.mnot.net/
Received on Friday, 27 February 2009 07:16:28 GMT

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