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Re: proposed reply to Re: OWL S&AS: Translation to RDF Graphs

From: Jim Hendler <hendler@cs.umd.edu>
Date: Wed, 14 May 2003 17:22:45 -0400
Message-Id: <p05200f6abae85968b5fb@[129.2.176.174]>
To: "Peter F. Patel-Schneider" <pfps@research.bell-labs.com>, www-webont-wg@w3.org
Cc: Dan Connolly <connolly@w3.org>, Guus Schreiber <schreiber@cs.vu.nl>

Peter-
  I'm okay w/this one -- Dan C. - I know Peter doesn't cite that much 
direct in this, but I think in this case it should be okay, since it 
is primarily saying that this is in a different document (first two 
parts) or making technical arguments (latter part).  Guus?
  -JH



At 1:06 PM -0400 5/14/03, Peter F. Patel-Schneider wrote:
>From: Dave Beckett <dave.beckett@bristol.ac.uk>
>Subject: OWL S&AS: Translation to RDF Graphs
>Date: Fri, 09 May 2003 19:33:00 +0100
>
>
>Thank you for your comments.
>
>>    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.
>>
>>  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.
>
>A normative definition of this is very likely to be no more intelligible
>than the current sitation.  A non-normative and incomplete, but more
>comprehensible discussion would be useful.  The Guide
>(http://www.w3.org/TR/owl-guide/ serves as at least a partial vehicle for
>this purpose.
>
>>   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.
>
>Agreed, but the Guide serves this purpose.
>
>>   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.
>
>There are at least the following sources of non-determinism
>
>1/ Optional rdf:type triples.
>    These mostly serve the purpose of allowing existing RDF documents to be
>    augmented with more information and thereby made into OWL DL documents,
>    as in
>         ....
>	foo rdf:type rdf:Property .
>	....
>	foo rdf:type owl:AnnotationProperty .
>
>2/ Allowing for only a skeleton of owl:sameIndividual, owl:differentFrom,
>    owl:equivalentClass, owl:disjointFrom, etc., triples to be present, as in
>	ex:a owl:differentFrom ex:b .
>	ex:b owl:differentFrom ex:c .
>	ex:c owl:differentFrom ex:d .
>	ex:d owl:differentFrom ex:a .
>	ex:d owl:differentFrom ex:b .
>	ex:d owl:differentFrom ex:c .
>    This allows for more flexibility.
>
>3/ Multiple ways of providing distinct individuals in the triples.
>    Fixing this would require a special syntax in the abstract syntax for
>    AllDifferent.
>
>All these have utility.  Removing them would result in fewer OWL DL and OWL
>Lite graphs, and would remove some graphs that can be imagined to be
>naturally produced.
>
>>       I note that several of these are related to having owl:Class and
>>       rdfs:Class, a separate issue.
>>
>>  Thanks
>>
>>  Dave
>
>
>Please reply to this message indicating whether anything more needs to be
>done in this area.
>
>Peter F. Patel-Schneider
>Bell Labs Research
>Lucent Technologies

-- 
Professor James Hendler				  hendler@cs.umd.edu
Director, Semantic Web and Agent Technologies	  301-405-2696
Maryland Information and Network Dynamics Lab.	  301-405-6707 (Fax)
Univ of Maryland, College Park, MD 20742	  240-731-3822 (Cell)
http://www.cs.umd.edu/users/hendler
Received on Wednesday, 14 May 2003 17:22:57 GMT

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