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[Fwd: Using XMLNS in link/@rel]

From: Dan Brickley <danbri@danbri.org>
Date: Fri, 27 Feb 2009 10:31:57 +0100
Message-ID: <49A7B30D.1080406@danbri.org>
To: Ben Adida <ben@adida.net>, RDFa <public-rdf-in-xhtml-tf@w3.org>
CC: Mark Nottingham <mnot@mnot.net>

Ben,

Can you respond to Mark?

Dan

-------- Original Message --------
Subject: Using XMLNS in link/@rel
Resent-Date: Fri, 27 Feb 2009 07:16:31 +0000
Resent-From: www-tag@w3.org
Date: Fri, 27 Feb 2009 18:15:45 +1100
From: Mark Nottingham <	>
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 09:32:42 GMT

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