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RE: timbl-03 collection clutter

From: Graham Klyne <gk@ninebynine.org>
Date: Tue, 06 May 2003 22:26:09 +0100
Message-Id: <>
To: Dan Connolly <connolly@w3.org>, Jeremy Carroll <jjc@hplb.hpl.hp.com>
Cc: Pat Hayes <phayes@ai.uwf.edu>, w3c-rdfcore-wg@w3.org

At 08:57 06/05/2003 -0500, Dan Connolly wrote:
>ACTION 20030425#5 danc figure out the cost to WebOnt of accepting
>where timbl-03 is short for
>The relevant bit of the OWL spec is:
>"the ontologies in O, taken together, provide a type for every
>individual ID;"
>  -- Web Ontology Language (OWL) Abstract Syntax and Semantics
>Section 4. Mapping to RDF Graphs
>  http://www.w3.org/TR/owl-semantics/mapping.html#4.1
>And without the rdf:List triples, the collection syntax
>doesn't meet that constraint.
>Jeremy and Peter discussed the cost of relaxing that constraint,
>and it seems, to me, to be considerable: the details of the
>mapping of owl-dl-abstract-syntax to RDF graphs are somewhat
>subtle and impact many parts of the S&AS spec, especially
>the semantic layering bits.

I'm a bit puzzled by this comment.  The mapping in AS&S 4.1 describes how 
to convert OWL abstract syntax into triples.  What we are discussing is 
whether an RDF parser needs to generate these additional triples (which are 
in any case entailed in any RDFS-interpretation).  I don't see how the 
semantics of OWL abstract syntax can reasonably be dependent on the 
behaviour of an RDF parser.

The AS&S is clear that the model theoretic definition of the semantics is 
authoritative [1].

I really can't see that it's coherent to have OWL semantics dependent on 
details or RDF parser performance that are quite meaningless (sic) at the 
RDFS level.  If nothing else, it violates the RDF semantics spec [2].

If nothing else, I think that this "subtle interaction" needs to be 
explained somewhere.


[1] http://www.w3.org/TR/owl-semantics/#1
For such OWL ontologies the direct model theory is authoritative and the 
RDFS-compatible model theory is secondary.

[2] http://www.w3.org/TR/rdf-mt/#intro
Semantic extensions of RDF MUST conform to the semantic conditions for 
simple and RDF entailment described in sections 1 and 3.1 of this document. 
Any name for entailment in a semantic extension SHOULD be indicated by the 
use of a vocabulary entailment  term. The semantic conditions imposed on an 
RDF semantic extension MUST define a notion of vocabulary entailment which 
is valid according to the model-theoretic semantics described in the 
normative parts of this document; except that if the semantic extension is 
defined on some syntactically restricted subset of RDF graphs, then the 
semantic conditions need only apply to this subset.

Graham Klyne
PGP: 0FAA 69FF C083 000B A2E9  A131 01B9 1C7A DBCA CB5E
Received on Tuesday, 6 May 2003 17:33:06 UTC

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