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RE: Proposal to resolve ISSUE-86

From: Boris Motik <boris.motik@comlab.ox.ac.uk>
Date: Thu, 27 Mar 2008 08:27:45 -0000
To: "'Michael Smith'" <msmith@clarkparsia.com>, "'public-owl-wg'" <public-owl-wg@w3.org>
Message-ID: <000301c88fe4$6f001150$4012a8c0@wolf>

Hello,

I see quite a bit of value in Mike's proposals 2 and 3. In fact, I would be quite happy with 2. I was advocating roundtripping
earlier quite strongly but have changed my mind: the constraints of the RDF syntax are such that achieving full syntactic
roundtrippability seems to get harder by the day. Therefore, I'm fine if saving an ontology into RDF and loading it back does not
give you an ontology that is syntactically exactly the same, as long as the original and the resulting ontologies are semantically
equivalent.

If we were to choose proposal 2, it seems to me that the lack for roundtrippability should have no practical impact at all; hence,
given the simplicity of the change, this solution seems to me to be a really good choice.

Regards,

	Boris

> -----Original Message-----
> From: public-owl-wg-request@w3.org [mailto:public-owl-wg-request@w3.org] On Behalf Of Michael Smith
> Sent: 26 March 2008 21:10
> To: public-owl-wg
> Subject: RE: Proposal to resolve ISSUE-86
> 
> 
> The problem, as presented in ISSUE-86 is the representation of inverse
> object properties in *facts*, i.e., ObjectPropertyAssertions.  I find it
> easy to get confused when we add to the discussion the use of object
> property expressions in restrictions, which does not have a problem in
> RDF.  I've limited my comments below to focus on object property
> assertions.
> 
> 
> Reusing the example fact from Boris's email [1],
> 
> ?(1) ObjectPropertyAssertion( InverseObjectProperty( P ) i1 i2 )
> 
> 
> Proposal #1) Disallow this by modifying the definition of
> ObjectPropertyAssertion.  The following axiom (2) is logically
> equivalent.
> 
> (2) ObjectPropertyAssertion( P i2 i1 )
> 
> 
> I believe this restriction matches OWL 1.0.  It was said on the telecon
> that this does not meet the requirements of some stakeholders, the DIG
> community in particular was mentioned.  This brings us to
> 
> ?
> Proposal #2) Allow these facts in the functional syntax but invert the
> assertion prior to the mapping to RDF.
> 
> This allows (1) in the functional syntax but serializing it in RDF as
> (2).  Thus, it is not round-trippable through RDF.
> 
> To which I'm sure some will reply that round-tripping through RDF is
> necessary.  So,
> 
> 
> Proposal #3) Allow these facts in the functional syntax but invert them
> and add an annotation prior to the mapping to RDF.
> 
> So (1) would be mapped to the following (3) before going to RDF.
> 
> (3) ObjectPropertyAssertion (
> 	Annotation( owl11:invertedObjectPropertyAssertion "true"^^xsd:boolean )
> 	P i2 i1
> 	)
> 
> The annotation facilitates round tripping. I don't think that the
> details of the annotation are important, only its presence, and consider
> the example above replaceable.  I find this solution attractive because
> it limits the solution to the RDF to/from FS mapping, which reflects
> where the problem is.  The triple level details of this solution are
> dependent on the resolution of issues related to the mapping of
> annotations on axioms.
> 
> 
> I prefer any of the proposals outlined above to those proposed which
> require minting canonical inverse URIs for every property.
> 
> Further, I believe that the approaches here will produce a more elegant
> behavior in OWL 1.0 and RDFS tools that are not explicitly updated for
> OWL 1.1.
> 
> 
> Regards,
> --
> Mike Smith
> 
> Clark & Parsia
> 
> [1] ?http://www.w3.org/mid/001801c88f7b$10383e90$4012a8c0@wolf
> 
Received on Thursday, 27 March 2008 08:29:12 GMT

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