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Re: PROPOSAL: Errata text to deal with the issue of predeclared 'xml' and 'xmlns' prefixes

From: Philip Taylor <pjt47@cam.ac.uk>
Date: Thu, 24 Sep 2009 22:27:40 +0100
Message-ID: <4ABBE44C.60606@cam.ac.uk>
To: Shane McCarron <shane@aptest.com>
CC: "public-rdf-in-xhtml-tf.w3.org" <public-rdf-in-xhtml-tf@w3.org>
Shane McCarron wrote:
> [...] I was just trying to reflect in 
> errata the discussion that went on today on the RDFa Task Force call.
> Would you prefer that we turn this around, explicitly indicating that 
> 'xmlns' is not permitted at all, and that 'xml' is only permitted to be 
> used in CURIEs if it is declared?

Mostly I want there to be a single unambiguous mapping from any given 
source document to a set of triples, so I really don't want the spec to 
say "a conforming RDFa Processor MAY provide these mappings" and 
introduce uncertainty - it should be a strict requirement one way or the 
other.

In this case I believe the current spec text is requiring that the 
mappings must not be provided, and so an errata that says they must be 
provided would be changing the normative behaviour defined by the spec, 
which seems undesirable. If it's unclear to implementors, it would be 
good to have test cases for this; I'd be happy to leave the spec as it 
is, though I'd also be happy for the spec to have explicit text to guide 
implementors safely around the confusion caused by XML Namespaces.

(Several implementors also have pre-defined mappings for other prefixes 
like 'rdf' and 'rdfs', and in one case also 'dc', 'foaf', 'owl', 'xv', 
'xsd', and maybe more. I believe none of these are permitted regardless 
of how one interprets XML Namespaces, so these are certainly bugs, and 
hopefully 'xml'/'xmlns' prefix handling can be fixed at the same time as 
those other bugs.)

-- 
Philip Taylor
pjt47@cam.ac.uk
Received on Thursday, 24 September 2009 21:28:22 GMT

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