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RE: OWL S&AS: Translation to RDF Graphs [proposed reply]

From: Jeremy Carroll <jjc@hplb.hpl.hp.com>
Date: Tue, 17 Jun 2003 10:40:23 +0200
To: "Dan Connolly" <connolly@w3.org>, <www-webont-wg@w3.org>
Message-ID: <BHEGLCKMOHGLGNOKPGHDMELOCBAA.jjc@hpl.hp.com>


It might be worth mentioning something about CR/PR ...
the guts of the criticism is that this is too hard to implement, and a good
response is to demonstrate implementations.

I believe we could commit ourselves to two independently developed OWL
Syntax Checkers, at least one of which does the reverse mapping (both Sean
and I seem to be close enough to make that reasonable: Sean does the reverse
mapping, the Jena team still needs to decide whether we even want that
functionality)

Jeremy




> -----Original Message-----
> From: www-webont-wg-request@w3.org
> [mailto:www-webont-wg-request@w3.org]On Behalf Of Dan Connolly
> Sent: 17 June 2003 03:10
> To: www-webont-wg@w3.org
> Subject: Re: OWL S&AS: Translation to RDF Graphs [proposed reply]
>
>
>
> [I took the ball on this in the 12Jun telcon...
> I supplemented the issues list with a link
> from issue 5.26 to Seans "Parsing OWL" as
> we discussed, and I cited the "rules
> of thumb" appendix.
>
> But frankly, we're really thin on *why* we
> decided what we decided re issue 5.26.
> I think it comes down to: of the designs that
> were available, the WG was more confident
> it could finish one than the others. But
> even that rationale isn't clearly justified.
>
> So the following is the best I could come up with based
> on what we've got. I don't think I'd find it
> very satisfactory if I were Dave; it comes very close
> to "we're tired of talking about this; go away."
> 1/2 ;-)
> ]
>
> On Fri, 2003-05-09 at 13:33, Dave Beckett wrote:
> >   OWL Web Ontology Language Semantics and Abstract Syntax
> >   W3C Working Draft 31 March 2003
> >
> >   4.1. Translation to RDF Graphs
> >   http://www.w3.org/TR/2003/WD-owl-semantics-20030331/mapping.html#4.1
> >
> > This transformation table gives the mapping from OWL's abstract
> > syntax to RDF triples which means that if you have an OWL ontology in
> > the abstract syntax you can write it in OWL's transfer syntax -
> RDF triples.
> >
> > It is however more difficult to see how to go from RDF triples to
> > OWL's abstract syntax.  As a semantic web technology, OWL builds on
> > RDF triples (and RDF on XML for syntax, URIs etc.) and this form of
> > presentation makes it harder to see how to start with RDF and gain
> > from OWL vocabulary.
>
> Discussion of whether and how to specify mappings between OWL abstract
> syntax and RDF graph syntax is the subject of this issue:
>
>   5.26-OWL DL Sytntax
>   http://www.w3.org/2001/sw/WebOnt/webont-issues.html#I5.26-OWLDLSyntax
>
> The working group discussed various alternatives, but eventually
> decided, 27 March 2003, on the design in the last call document.
> Note the outstanding dissent:
>
>   5.26 OWL DL Syntax - Formal Objection
>   From: Jeremy Carroll (jjc@hpl.hp.com)
>   Date: Fri, Mar 28 2003
>   http://lists.w3.org/Archives/Public/www-webont-wg/2003Mar/0264.html
>
> While the points in your comment are well-made, they don't seem
> to provide new information which would justify reopening
> the issue.
>
> You may be interested in continued related work, meanwhile...
>
>
> > In detail:
> >
> >  1) This presentation may make it hard to see how to transfer OWL -
> >    from the transfer syntax (RDF triples) to the OWL abstract syntax.
> >
> >    Running the (non-deterministic!) mapping rules backwards seems the
> >    only way and is up to each implementer to work out how to do that.
> >    Giving this mapping explicitly would be beneficial.  If it depends
> >    on the OWL subset in use, this should also be described.  All of
> >    this should preferably have and be linked to test cases.
>
> You may be interested in some related work by individuals in the
> working group:
>
> Parsing OWL, Sean Bechhofer, University of Manchester, June 02 2003
> http://wonderweb.semanticweb.org/owl/parsing.shtml
>
> While this doesn't provide an actual specification of the reverse
> mapping, it does "describe a basic strategy that could be used ...
> to construct an OWL ontology that corresponds to the triples
> represented in the RDF"
>
>
> >  2) It is not clear from this mapping what restrictions there are on
> >    any existing RDF such that it would already be legal OWL DL or OWL
> >    Lite (apart from trying it out with an OWL validator).
> >
> >    If the path from RDF to anything but OWL Full is not clear, it
> >    seems that it is unlikely that benefits of OWL DL or OWL Lite will
> >    be wholly realised.
>
> In order to clarify the path from RDF to OWL DL,
> informative section is being added to the OWL Reference:
>
>   Appendix E. Rules of Thumb for OWL DL ontologies
>   http://www.daml.org/2002/06/webont/owl-ref-proposed#app-DLinRDF
>
>
> >  3) The optional and non-deterministic mappings to/from triples are a
> >    bad idea that are likely to cause interoperability problems and
> >    make the mappings harder.  I urge you to consider removing such
> >    non-determinism.
>
> Note that "non-deterministic" does not mean "not completely specified";
> it just means "not 1-1"; i.e. one abstract syntax structure corresponds
> to a number of RDF graphs. For example, for the intersection
> of classes A, B, and C, it doesn't matter what order they appear
> in an RDF collection.
>
> Taken literally, your request is to specify that exactly one RDF
> graph is allowed for any OWL abstract syntax structure. Could
> you confirm that this is what you're suggesting? It seems unlikely.
>
>
> >      I note that several of these are related to having owl:Class and
> >      rdfs:Class, a separate issue.
> >
> > Thanks
> >
> > Dave
>
> Please let us know if you find this response satisfactory.
>
> --
> Dan Connolly, W3C http://www.w3.org/People/Connolly/
>
>
>
Received on Tuesday, 17 June 2003 04:40:34 GMT

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