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

From: Shane McCarron <shane@aptest.com>
Date: Thu, 24 Sep 2009 16:06:21 -0500
Message-ID: <4ABBDF4D.2020800@aptest.com>
To: Philip Taylor <pjt47@cam.ac.uk>
CC: "public-rdf-in-xhtml-tf.w3.org" <public-rdf-in-xhtml-tf@w3.org>
Philip,

Comments inline:

Philip Taylor wrote:
> Shane McCarron wrote:
>> [...] Unfortunately, this version of the RDFa Syntax Recommendation 
>> is silent on whether these prefix mappings are required to be 
>> included in the collection of URI mappings at the start of processing.
>
> Isn't it actually very explicit that they are not included? It defines 
> the processing model algorithm with:
>
>   "An initially empty list of [URI mapping]s, called the [local list 
> of URI mappings]."
>
> and a list that contains mappings for xml and xmlns at the start of 
> processing is not initially empty.
> Then the local list of URI mappings is never modified except via:
>
>   "Next the [current element] is parsed for [URI mapping]s and these 
> are added to the [local list of URI mappings]. [...] Mappings are 
> provided by @xmlns. The value to be mapped is set by the XML namespace 
> prefix, and the value to map is the value of the attribute—a URI."
>
> so it will only add mappings that are explicitly declared in xmlns:* 
> attributes in the document. So I can't see any way to interpret the 
> spec that would allow xml and xmlns to be automatically bound.
Yeah - that's true...  However, it is in conflict with the bit of 
Namespaces in XML that we care about.  That spec has rules for what can 
be put in a document (syntactically) and intermingled with those rules 
indicates that 'xml' and 'xmlns' are effectively predeclared.  So, I can 
see how some implementor could have mis-interpreted our intent.  I could 
just as easily go the other way on this.  I don't care really, since to 
me neither of those prefixes can ever name a vocabulary that I would 
want to reference in RDF.

>
> Also, I remember it being mentioned several times on the lists that 
> RDFa merely imports the namespace syntax from Namespaces in XML, and 
> nothing else, and it could just as easily call the attribute e.g. 
> 'banana' instead of 'xmlns'. That view seems to conflict with the idea 
> that the default xml/xmlns mappings are imported too.

See above, but in general I agree.  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?

-- 
Shane P. McCarron                          Phone: +1 763 786-8160 x120
Managing Director                            Fax: +1 763 786-8180
ApTest Minnesota                            Inet: shane@aptest.com
Received on Thursday, 24 September 2009 21:07:04 GMT

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