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Re: Exact format for XML Literals?

From: Ivan Herman <ivan@w3.org>
Date: Wed, 09 Sep 2009 12:52:14 +0200
Message-ID: <4AA788DE.8010108@w3.org>
To: Axel Polleres <axel.polleres@deri.org>
CC: W3C SPARQL Working Group <public-rdf-dawg@w3.org>
Axel, that quote is in the RDF Concept standard[1], the SPARQL group
will not change that...

What I think we ought to do is to put something like the RDF/XML spec
says, ie, that the literal in the graph pattern is 'transformed' into an
RDF XML Literal.

Ivan



[1] http://www.w3.org/TR/rdf-concepts

Axel Polleres wrote:
> I guess just dropping
> "
>> - for which encoding as UTF-8 [RFC 2279] yields exclusive Canonical XML
>> [...][XML-XC14N]
> "
> is not sufficient?
> 
> I.e. aren't the first and third item enough? 
> What do I miss here? 
> 
> Thanks,
> Axel
> 
> On 8 Sep 2009, at 08:24, Ivan Herman wrote:
> 
>> Guys,
>>
>> an issue came up in the RDFa task force that has relevance on the SPARQL
>> syntax. It may be that this will lead to a need to tighten up the SPARQL
>> language specification's language (no new feature here). It is related
>> to the way XML Literals are represented in the query language (well,
>> essentially, in Turtle...). The question is whether the following
>> extract is valid or not:
>>
>> a:bla b:blabla
>>  "<bla   b='something' a='else'>and else</bla>"^^rdf:XMLLiteral.
>>
>> The lexical space of XML Literal is defined by the RDF concept document
>> and it says:
>>
>> [[[
>> The lexical space is the set of all strings:
>> - which are well-balanced, self-contained XML content [XML];
>> - for which encoding as UTF-8 [RFC 2279] yields exclusive Canonical XML
>> [...][XML-XC14N]
>> - for which embedding between an arbitrary XML start tag and an end tag
>> yields a document conforming to XML Namespaces [XML-NS]
>> ]]]
>>
>> the important point is the usage of XC14N. A cursory read of this text
>> would mean that, in SPARQL, one would have to write a canonical XML for
>> an XML Literal (which is not the case in the case above).
>>
>> Note that the RDF/XML specification goes a little bit further: in point
>> 7.2.17 of the RDF/XML spec[2] it explicitly
>>
>> [[[
>> l is transformed into the lexical form of an XML literal in the RDF graph
>> ]]]
>>
>> and refers to the XC14N algorithm explicitly. Ie, the XML extract above
>> is perfectly valid for RDF/XML. However, the current SPARQL spec is
>> silent about this.
>>
>> It is fairly obvious that the same should happen in SPARQL (and in
>> Turtle): the parser should, conceptually, apply a canonicalization
>> algorithm on the XML content in the literal. But it may be better to say
>> that explicitly in the document, similarly to RDF/XML...
>>
>> Do I miss something?
>>
>> Ivan
>>
>> [1] http://www.w3.org/TR/rdf-concepts/#section-XMLLiteral
>> [2] http://www.w3.org/TR/rdf-syntax-grammar/#section-grammar-productions
>>
>> -- 
>>
>> Ivan Herman, W3C Semantic Web Activity Lead
>> Home: http://www.w3.org/People/Ivan/
>> mobile: +31-641044153
>> PGP Key: http://www.ivan-herman.net/pgpkey.html
>> FOAF: http://www.ivan-herman.net/foaf.rdf
> 
> -- 
> Dr. Axel Polleres
> Digital Enterprise Research Institute, National University of Ireland,
> Galway
> email: axel.polleres@deri.org <mailto:axel.polleres@deri.org>  url:
> http://www.polleres.net/
> 
> 
> 

-- 

Ivan Herman, W3C Semantic Web Activity Lead
Home: http://www.w3.org/People/Ivan/
mobile: +31-641044153
PGP Key: http://www.ivan-herman.net/pgpkey.html
FOAF: http://www.ivan-herman.net/foaf.rdf

Received on Wednesday, 9 September 2009 10:52:54 GMT

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