W3C home > Mailing lists > Public > public-rdf-in-xhtml-tf@w3.org > July 2009

Re: HTML+RDFa Issues (update)

From: Julian Reschke <julian.reschke@gmx.de>
Date: Thu, 02 Jul 2009 19:31:37 +0200
Message-ID: <4A4CEEF9.9040702@gmx.de>
To: Sam Ruby <rubys@intertwingly.net>
CC: Manu Sporny <msporny@digitalbazaar.com>, RDFa mailing list <public-rdf-in-xhtml-tf@w3.org>
Sam Ruby wrote:
> Manu Sporny wrote:
>> = Use of regular CURIEs in @rel =
>> I believe that Julian Reschke has raised this issue several times. I
>> don't remember the technical issue and I remember Ben stating clearly
>> that there isn't a technical issue.
>> I don't have any input on this at the present time. Clearly, if a
>> technical issue exists with CURIEs in @rel - we must address it.
> If I remember correctly, the issue that Julian raised is that a number 
> of potential "consumers" have created multiple, potentially incompatible 
> ways of interpreting the value of the rel attribute.  Some may interpret 
> it as a list of tokens, some as a list of URIs, and some as a list of 

Indeed. Note that the two interpretations are somewhat compatible, while 
the CURIE interpretation is not.

> The technical issue is that it is theoretically possible to construct a 
> rel value which has a list of URIs which could be accidentally 
> interpreted as a list of CURIEs.  Consider the following:
> <a xmlns:urn="http://purl.org/dc/terms/"
>    rel="urn:rights urn:uuid:1225c695-cfb8-4ebb-aaaa-80da344efa6a"
>    href="http://example.com/terms_of_service.html" >
> My take: while it is possible to construct such examples, in practice 
> they would be rare enough to not be an issue.  That being said, it is 
> nearly impossible to legislate against, as it would require people to 
> avoid declaring namespaces prefix that matches any current or future URI 
> scheme.  Perhaps a "SHOULD avoid well known URI schemes" might be in order.

That would deal with collisions; but not with the fact that existing, 
non-RDFa consumers, will not expect that an indirection mechanism has 
been added.

(And yes, I'm familiar with the P.O.V. that HTML4 requires new rel 
values to be opted-in through a @profile; however the real world shows 
almost nobody has been doing it, *including* RDFa).

BR, Julian
Received on Thursday, 2 July 2009 17:32:29 UTC

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