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Re: Exact format for XML Literals?

From: Axel Polleres <axel.polleres@deri.org>
Date: Wed, 9 Sep 2009 10:52:45 +0100
Cc: "W3C SPARQL Working Group" <public-rdf-dawg@w3.org>
Message-Id: <7DCDAF6B-C975-49EE-8DCC-F150E3728546@deri.org>
To: Ivan Herman <ivan@w3.org>
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  url: http://www.polleres.net/
Received on Wednesday, 9 September 2009 09:53:29 GMT

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