W3C home > Mailing lists > Public > public-lld@w3.org > October 2010

RE: Returning to OWL and application profiles

From: Young,Jeff (OR) <jyoung@oclc.org>
Date: Mon, 11 Oct 2010 21:14:51 -0400
Message-ID: <43b201cb69aa$d7cc0656$d71dae84@oa.oclc.org>
To: "Mikael Nilsson" <mikael@nilsson.name>
Cc: <public-lld@w3.org>
My sense is that OWL reasoning is an excellent abstract solution and don't think we should be overly concerned by the need for inferencing. I gave an example of a mechanical relationship between OWL and XML Schema to do "record validation". I suspect that RIF could do even better, but I admit more examples are needed.

Jeff

Mikael Nilsson <mikael@nilsson.name> wrote:

mån 2010-10-11 klockan 17:05 -0400 skrev Young,Jeff (OR):
> Mikael,
> 
> I think it would be better to encourage the use of owl:subClassOf and
> owl:subPropertyOf to resolve this scenario instead. For example:
> 
> General-purpose class:
> foo:Widget a owl:Class .
> 
> General-purpose property:
> bar:title a owl:Property .
> 
> Limited-purpose domain:
> baz:Widget owl:subClassOf foo:Widget.
> baz:title owl:subPropertyOf bar:title .
> 
> Domain-specific cardinalities can be applied to terms in the
> domain-specific ontology without creating general semantic clashes.
> Other limited-purpose domains could do the same.

Yes, that sort of solves the contradiction issue. 

But still, if a cardinality constraint is not met, an OWL reasoner is
expected to produce additional statements or infer the equality of some
of the values. This still does not amount to a "record validation" tool,
unfortunately.

/Mikael 


> 
> Jeff
> 
> > -----Original Message-----
> > From: public-lld-request@w3.org [mailto:public-lld-request@w3.org] On
> > Behalf Of Mikael Nilsson
> > Sent: Monday, October 11, 2010 10:15 AM
> > To: public-lld@w3.org
> > Subject: Returning to OWL and application profiles
> > 
> > Hi all!
> > 
> > I'm in the middle of finalizing my thesis on metadata interoperability
> > and harmonization, and I'm right now formulating a section on RDF and
> > application profiles, so the discussion I saw here comes at an
> > interesting time for me :-)
> > 
> > The issue from my point of view with using OWL for defining RDF
> > application profiles, is that APs define domain-specific structural
> > constraints while OWL adds semantics to existing classes.
> > 
> > I.e. if I produce an OWL-based AP saying that the cardinality of
> > dc:title is exactly 1, for a specific class, and someone else produces
> > an OWL-based AP saying that the cardinality is 2 for the same class,
> > the
> > result is a *contradiction*.
> > 
> > This differs substantially from the case with application profiles,
> > where the cardinality is not seen as part of the semantics of a class,
> > but rather part of a set of restrictions, external to and independent
> > of
> > the class. Multiple incompatible application profiles are perfectly
> > normal.
> > 
> > Therefore, publishing an OWL ontology defining domain-specific
> > semantics
> > for certain classes or properties is just as bad practice as if someone
> > produces an RDF Schema saying the range of dct:creator is
> > myorg:Employee. This defines new semantics of dct:creator, something
> > that is simply not true, and can cause involuntary contradictions.
> > 
> > The other issue is the open world assumption that I saw Pete mention,
> > i.e. the fact that if an OWL ontology specifies a cardinality of 2 for
> > dc:title, and only one is found, this results in the generation of a
> > new
> > dc:title statement, not in non-validity of the record.
> > 
> > Thus, we would need an alternative semantics for OWL to perform
> > validation.
> > 
> > But that's exactly it - the semantics is "alternative" and on its face,
> > the semantics of the published OWL file is something else entirely.
> > 
> > As a concrete example, if I serve an OWL file from my web server, using
> > application/rdf+xml as suggested by the OWL specs [1], the
> > interpretation will be as RDF triples using the RDF and OWL built-in
> > semantics, thus resulting in the generation of new triples, potentially
> > contradiction with other ontologies, and not in validation as expected.
> > 
> > What *would* work is using application profile specific classes for
> > each
> > separate OWL-based AP, and only constraining them, but that might
> > appear
> > a bit cludgy.
> > 
> > So, I'm a bit unsure regarding using non-standard semantics of OWL. I
> > don't really see a clean solution at the moment.
> > 
> > /Mikael
> > 
> > [1] http://www.w3.org/TR/owl-ref/#MIMEType
> > 
> > 
> 
Received on Tuesday, 12 October 2010 01:15:09 GMT

This archive was generated by hypermail 2.2.0+W3C-0.50 : Tuesday, 12 October 2010 01:15:11 GMT