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Re: HTML+RDFa Issues (update)

From: Julian Reschke <julian.reschke@gmx.de>
Date: Thu, 09 Jul 2009 19:16:11 +0200
Message-ID: <4A5625DB.8070600@gmx.de>
To: Toby Inkster <tai@g5n.co.uk>
CC: Manu Sporny <msporny@digitalbazaar.com>, RDFa mailing list <public-rdf-in-xhtml-tf@w3.org>
Toby Inkster wrote:
> On Thu, 2009-07-09 at 16:58 +0200, Julian Reschke wrote:
>> If I had a solution that is compatible both with RDFa and full-URIs in
>> @rel, I would already have proposed it. That's why I've been
>> complaining for so long: I think the use of CURIEs instead of
>> safe-CURIEs in @rel is a big problem. (It's ok in new attributes, but
>> problematic in @rel/rev).
> 
> Safe CURIEs are important in @about/@resource because those attributes
> are primarily intended for URIs. The @rel attribute was not previously
> used for URIs, so no disambiguation mechanism was needed.

The @rel attribute previously existed, and was not specified to use 
CURIE indirection, thus the change introduced by RDFa (not qualified by 
@profile, btw) potentially changes the meaning of existing content.

Furthermore, RDFa is not specified (yet) for HTML; so the interpretation 
of @rel depends on the context it appears in (such as DOCTYPE). This is 
bad, because in many cases the final consumer of the @rel value (think 
XSLT) will not know about the context.

> Yes, @rel in *Atom* is a URI, but no previous recommendations for HTML
> or XHTML have recommended URIs in @rel, and the current HTML5 draft
> doesn't either. Nor am I aware of any widely non-W3C specifications that
> use URIs in @rel. Google's rel=canonical and rel=nofollow are simple
> tokens. Pingback uses a simple token, and so do microformats. So I'm not
> sure where these pre-existing uses of URIs in @rel are supposed to be
> found.
> 
> If you're concerned by compatibility between HTML's @rel and Atom's
> @rel, then don't be. They're completely incompatible. Atom's is not a
> token separated list at all.

No, I'm not concerned about the difference to Atom. What I'm concerned 
with is the difference to RDFa-less XHTML and HTML.

BR, Julian
Received on Thursday, 9 July 2009 17:16:57 GMT

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