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

Re: Updated RDFa-in-text/html tests

From: Shane McCarron <shane@aptest.com>
Date: Fri, 05 Jun 2009 10:17:24 -0500
Message-ID: <4A293704.3060007@aptest.com>
To: Mark Birbeck <mark.birbeck@webbackplane.com>
CC: Jeni Tennison <jeni@jenitennison.com>, Philip Taylor <pjt47@cam.ac.uk>, RDFa mailing list <public-rdf-in-xhtml-tf@w3.org>


Mark Birbeck wrote:
> Hi Shane,
>
>   
>> FWIW - RDFa requires the use of XML Namespaces 1.0, not 1.1.  As a result, I
>> think that both of these tests are wrong.  As Philip points out, in XML
>> Namespaces 1.0 an empty xmlns value is illegal, so such a value MUST be
>> ignored by an RDFa processor.  My implementation does not correctly do that,
>> but I am updating it right now.
>>     
>
> I'm not totally convinced we can get around this so easily.
>
> First, the RDFa spec doesn't refer to XML namespace processing as
> such, but simply to the XML namespace attribute technique:
>
>   "In RDFa these mappings are expressed using the XML namespace
>    syntax..."
>   
Well.... I disagree.  The Normative References of the RDFa Syntax 
Recommendation includes XML Namespaces 
(http://www.w3.org/TR/rdfa-syntax/#sec_D.1.)  Since this reference is 
normative, it means we have brought in all the normative requirements of 
that specification by reference.  These requirements include the 
requirement that an empty XML Namespace mapping is illegal.  I do agree 
that we could add clarifying text just so people don't need to guess 
about this.  I also think that it is reasonable to make that clarifying 
text generic.  I would support adding such text in an errata document or 
in an update to the Rec if one is coming out soon (or both).

>
> Anyway, as the spec stands at the moment, I think it is legitimate for
> processors to parse a prefix mapping that's empty, and then to use
> that in a CURIE.
>   

You are correct that, as it stands, if there were a legal way to define 
a mapping from some prefix to "", using that mapping would be 
legitimate.  As I said above, I would support an errata clarifying that 
this is NEVER ok.

Also, for avoidance of doubt here, I consider this a pathological edge 
case.   While I agree that processors should handle this case in a 
consistent manner, this is not the sort of thing I would expect to 
encounter in the wild - at least not in any page where the author 
expected to get triples out.

-- 
Shane P. McCarron                          Phone: +1 763 786-8160 x120
Managing Director                            Fax: +1 763 786-8180
ApTest Minnesota                            Inet: shane@aptest.com
Received on Friday, 5 June 2009 15:18:21 GMT

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