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

During discussions this week, Jeni and others pointed out that the 
Namespaces in XML Recommendation effectively predeclares a couple of 
prefixes, but that the RDFa Syntax Recommendation is silent on how these 
should be handled in conforming implementations.  we discussed this 
briefly on the call today.  I propose an errata entry to address the 
issue surrounding the presence of the 'xml' and 'xmlns' mappings:

Sections 5.5 step 2 and 5.4.1 bring in the concepts associated with 
Namespaces in XML as defined in [XMLNS].  One such concept  is that the 
prefix 'xml' is effectively predefined and has a required mapping, 
although it may also be declared in a document as long as it has the 
required mapping.  Another is that the prefix 'xmlns' also has a 
required mapping, but it cannot be declared in a document, even with 
that mapping.  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.  Consequently, a conforming RDFa Processor MAY provide these 
mappings.  For maximum portability, documents that wish to reference 
CURIEs via the 'xml' prefix SHOULD declare that prefix. For maximum 
portability, documents SHOULD NOT reference CURIEs via the 'xmlns' 
prefix (since it may not be present in some conforming RDFa Processors, 
and it is illegal to declare the prefix).  In a future version of this 
Recommendation, it is likely that RDFa Processors will be required to 
support the use of these prefixes in CURIEs without the need to declare 
them in the document.

Comments?

-- 
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 20:28:59 UTC