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Returning to OWL and application profiles

From: Mikael Nilsson <mikael@nilsson.name>
Date: Mon, 11 Oct 2010 16:14:56 +0200
To: public-lld@w3.org
Message-ID: <1286806496.4536.39.camel@daneel>
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 Monday, 11 October 2010 14:15:31 GMT

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