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Re: RDF model theory is now underspecified

From: Dave Beckett <dave.beckett@bristol.ac.uk>
Date: Mon, 18 Aug 2003 20:32:44 +0100
To: "Peter F. Patel-Schneider" <pfps@research.bell-labs.com>
Cc: www-rdf-comments@w3.org
Message-Id: <20030818203244.3e252116.dave.beckett@bristol.ac.uk>

On Mon, 18 Aug 2003 14:50:40 -0400 (EDT)
"Peter F. Patel-Schneider" <pfps@research.bell-labs.com> wrote:

> 
> 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
> 
<snip/>

> > 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.

It looks like I copied too much from the RDF Concepts wording since
the syntax WD has no "lexical to value mapping".  I will remove most
of this note from this working group editor's draft leaving mostly
just a pointer to the section in RDF concepts.


> > > <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?  

Since I'll be removing those words there, leaving them for RDF
concepts to deal with, so the answer to the above "remains unchanged"
will be yes.


> > > 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.

No, I have already answered that but I can repeat it:

   We had several implementor feedback reports on this point and made
   this change to reflect the reality of running code for XML schema
   datatypes.

We fixed the problems found by implementors with XSD detail, addressing
their concern with the changes to RDF Concepts (not in syntax, once I
revert the mis-paste).

> 
> > 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?

You cannot xsd-entail between rdf/xml documents.  RDF datatype
xsd-entailment is in the RDF Semantics document and happens between
RDF graphs.

So the question is meaningless in this form.  The RDF Semantics
editor can answer it if re-expressed in terms of triples.


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

There was no answer there to that ill-formed question either
in the LC drafts.

The mapping from the RDF concrete (RDF/XML) to RDF abstract syntax
(RDF triples) will remain well specified, implementable and
implemented, as already reported to the working group from
developers.

Dave
Received on Monday, 18 August 2003 15:34:47 GMT

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