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Re: support XML Literals in RDF (was Re: Test cases: XML Literal value space and exclusive canonicalization)

From: Dave Beckett <dave.beckett@bristol.ac.uk>
Date: Thu, 7 Aug 2003 12:22:00 +0100
To: "Peter F. Patel-Schneider" <pfps@research.bell-labs.com>
Cc: www-rdf-comments@w3.org, Martin Duerst <duerst@w3.org>
Message-Id: <20030807122200.1cd62881.dave.beckett@bristol.ac.uk>

On Thu, 07 Aug 2003 07:02:52 -0400
"Peter F. Patel-Schneider" <pfps@research.bell-labs.com> wrote:

> > Date: Thu, 7 Aug 2003 11:08:44 +0100
> > From: Dave Beckett <dave.beckett@bristol.ac.uk>
> > To: Martin Duerst <duerst@w3.org>
> > Cc: www-rdf-comments@w3.org, pat hayes <phayes@ihmc.us>, Benja Fallenstein <b.fallenstein@gmx.de>, Jeremy Carroll <jjc@hplb.hpl.hp.com>, w3c-rdfcore-wg@w3.org, w3c-i18n-ig@w3.org, msm@w3.org> 

> > On Mon, 04 Aug 2003 13:55:25 -0400
> > Martin Duerst <duerst@w3.org> wrote:
> > 
> > <snip/>
> >> So it seems to be true, for simple datatype literals, that
> >> 
> >> Abstract syntax == lexical value ~= representation in RDF/XML
> >> 
> >> (the ~= including generic issues such as character escaping,
> >> but no datatype-specific issues).
> > 
> > Yeah, sort of.  And the Unicode characters in the lexical form that
> > can't be written in XML.
> > 
> > <snip/>
> >  
> >> Is every RDF application required to support XML Literals?
> >> Or only the syntactic parts, and the RDF/XML to Graph conversion
> >> (including canonicalization) if appropriate?
> > 
> > Only those that deal with mapping between the abstract syntax and the
> > XML syntax (either direction).  
> > 
> > The "pure" RDF applications work on graphs and need have no XML-specific
> > code.  XML Literals just look like any other datatype to RDF graph
> > applications and should need no extra support in the graph.
> > 
> > <snip/>
> Although any RDF-only application, i.e., an application that *only* 
> needs to determine the RDF implications of an RDF graph, does not need 
> any special code to support XML Literals beyond the code needed to 
> support sequences of octets, an RDF application that goes beyond these 
> implications, for example to determine whether a literal is in LV, will 
> need considerable code to support XML Literals.

Any RDF application that doesn't do (RDF, RDFS, any) entailment does not
need this "considerable code".

> Also, any application that needs to determine the RDFS implications of 
> an RDF graph needs at least an oracle to determine whether a sequence of 
> octets is in the value space of rdf:XMLLiteral.

The RDF/XML rdf:parseType="Literal" exc-C14N  checks that for you, in
the parsing.

There are no octets in the graph.  The Unicode strings in the graph that
make up the lexical forms of XML literals will be in exc-C14N form, if
used via rdf:parseType="Ltieral" and require no XML code for your

If you had said datatype-entailment then that would be your oracle - an
XSD implementation library for example.  Such a "considerable code"
would likely have to include some XML support, since the X in XSD stands
for XML.  There seem to be such libraries freely already available.

Received on Thursday, 7 August 2003 07:24:21 GMT

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