RE: Comments on RDF/A Syntax (Editor's Draft 27 October 2005)

Dan,

On 28 November 2005 14:08 Dan Connolly wrote:
> On Nov 28, 2005, at 7:44 AM, Mark Birbeck wrote:
> [...]
> > So if you place RDF/XML into another document--say XHTML or SVG--an 
> > RDF/XML parser should be able to pick it out. For example, 
> in SVG you 
> > can embed RDF/XML in the metadata element, and an RDF/XML parser 
> > should be able to process that, even though it doesn't 'understand' 
> > the SVG that surrounds this data.
> 
> Not in all cases. The surrounding XML could quote or negate 
> the included RDF/XML.

If it did it using RDF/XML then obviously the parsing would start earlier,
and if it did it using some other language, then there's not much the
RDF/XML parser can do about it--you'd need some prior knowledge that this
was going to be the case.


> Parsers can only do this "peeking" when they've got some 
> particular reason (e.g. a command-line flag) to know that 
> embedded RDF/XML is to be taken literally.

I'm not talking about 'peeking', I'm talking about the normal behaviour of
RDF/XML parsers, which is to 'skip' XML elements and attributes until they
find one of the 'Grammar start' rules. Of course this might be rdf:RDF right
at the beginning of the document in which case there is nothing to 'skip',
but it might also be <x:y rdf:about="z">, halfway down a document. It's this
second feature I was trying to leverage in early work on RDF/A, and that is
the whole subject of this discussion. (I.e., Jeremy has asked why we can't
just use the RDF/XML attributes 'as is'.)


> [[
> The W3C TAG issue RDFinXHTML-35: Syntax and semantics for 
> embedding RDF in XHTML concerns this freedom in many other 
> cases, as well. A naive approach is to say that RDF/XML has 
> its usual meaning wherever it appears in any XML document. 
> But that would conflict with the existing practice using 
> RDF/XML in XSLT templates, not to mention any future practice 
> of quoting, quantifying, refuting, or commenting on embedded 
> RDF expressions.
> ]]
>   -- http://www.w3.org/2004/01/rdxh/specbg.html
> -> http://www.w3.org/2001/tag/issues.html?type=1#RDFinXHTML-35

I can only see from this that the intention is that you cannot simply
process any old document with an RDF/XML parser, and hope to get out
metadata that was perfectly bound to its intended purpose. However, I wasn't
talking about that--I was saying that if you wanted to pass a document that
*contained* RDF/XML into an RDF/XML parser, then a correctly implemented
parser will be able to cope with it.

Regards,

Mark


Mark Birbeck
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Received on Monday, 28 November 2005 14:28:56 UTC