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Re: RDF model theory is now underspecified

From: Peter F. Patel-Schneider <pfps@research.bell-labs.com>
Date: Mon, 18 Aug 2003 14:50:40 -0400 (EDT)
Message-Id: <20030818.145040.61829385.pfps@research.bell-labs.com>
To: dave.beckett@bristol.ac.uk
Cc: www-rdf-comments@w3.org

From: Dave Beckett <dave.beckett@bristol.ac.uk>
Subject: Re: RDF model theory is now underspecified
Date: Mon, 18 Aug 2003 19:26:08 +0100

> Since this is a question on the syntax draft, and not RDF Semantics
> at all, I'll reply.
> 
> On Mon, 18 Aug 2003 12:24:31 -0400 (EDT) "Peter F. Patel-Schneider"
> <pfps@research.bell-labs.com> wrote:
> > 
> > The current editor's draft of RDF Syntax
> > (http://www.w3.org/2001/sw/RDFCore/TR/WD-rdf-syntax-grammar-20030117/
> > dated 18 August 2003) contains the following new wording in a
> > normative note within Section 6.1.9
> > 
> >   During input processing of XML Schema Datatypes within RDF,
> >   software MAY apply the appropriate whitespace normalization
> >   immediately before the lexical to value mapping, and MAY produce a
> >   warning if any whitespace is changed in this normalization.
> 
> Read the document and the references to find out what MAY means.
> 
> This is also pretty much what the editor's draft of RDF concepts says
> on the matter, reworded to apply to the syntax data model mapping.
> 
> > Although ``input processing ... immediately before the lexical to
> > value mapping'' is not particularly well defined, I take this to mean
> > that the RDF Graph corresponding to
> 
> You give no specific problem with that phrase.

When and where does this input processing happen?   It seems strange that
``input processing'' happens ``immediately'' before some semantic
processing.  These two can happen at quite different times, even perhaps in
different programs.

> > 
> > <rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
> >          xmlns:eg="http://example.org/">
> > 
> >   <rdf:Description rdf:about="http://www.example.org/a">
> >     <eg:prop rdf:datatype="http://www.w3.org/2001/XMLSchema#int"> 3
> >     </eg:prop>
> >   </rdf:Description>
> > 
> > </rdf:RDF>
> > 
> > remains unchanged as 
> > 
> > <http://www.example.org/a> <http://example.org/prop> " 3
> > "^^<http://www.w3.org/2001/XMLSchema#int> .
> 
> It MAY.

Huh?  Does this mean that even the RDF graph that corresponds to a RDF/XML
document is underspecified?  

> > However, it appears to me that this note means that the RDF model
> > theory is now underspecified, as RDF software, including software that
> > computes entailments, may choose to treat 
> > 	" 3 "^^<http://www.w3.org/2001/XMLSchema#int> 
> > as denoting the integer three instead of some non-literal.  
> > 
> > I view this change as undesirable.
> 
> We had several implementor feedback reports on this point and made
> this change to reflect the reality of running code for XML schema
> datatypes.   Implementors now MAY make that entailment above.

This is then a serious source of incompatability between different RDF
implementations.

> The RDF Semantics document is not underspecified here, particularly
> since the running code we have had feedback on, implements it.
> 
> Dave

So, does

<rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
          xmlns:eg="http://example.org/">

   <rdf:Description rdf:about="http://www.example.org/a">
     <eg:prop rdf:datatype="http://www.w3.org/2001/XMLSchema#int"> 3 </eg:prop>
   </rdf:Description>
 
 </rdf:RDF>

xsd-entail

<rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
          xmlns:eg="http://example.org/">

   <rdf:Description rdf:about="http://www.example.org/a">
     <eg:prop rdf:datatype="http://www.w3.org/2001/XMLSchema#int">3</eg:prop>
   </rdf:Description>
 
 </rdf:RDF>

or not?

In the last-call specification it did not.  Now it appears that the answer
is that ``It depends.''  Thus my claim of underspecification.

Peter F. Patel-Schneider
Received on Monday, 18 August 2003 14:50:51 GMT

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