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[OWLWG-COMMENT] QCR problem in OWL 1.1 Full - action ?? from F2F

From: Michael Schneider <schneid@fzi.de>
Date: Thu, 13 Dec 2007 09:51:44 +0100
Message-ID: <0EF30CAA69519C4CB91D01481AEA06A05A5A98@judith.fzi.de>
To: <pfps@research.bell-labs.com>, "Owl Dev" <public-owl-dev@w3.org>
Cc: "Alan Ruttenberg" <alanruttenberg@gmail.com>, <ian.horrocks@comlab.ox.ac.uk>

[This is a comment to a discussion in the OWL-WG list;
also posted to WG members involved]

Hi Peter!

Peter F. Patel-Schneider wrote on Fri, 07 Dec 2007
in <http://lists.w3.org/Archives/Public/public-owl-wg/2007Dec/0095.html>

> Qualified Cardinalities in OWL 1.1 Full
> 
> 
> Suppose that we want to keep the general flavour of the OWL Full
> semantics *and* use the current OWL 1.1 mapping to RDF.  What would
> happen?
> 
> 
> Here is an example of how the RDF mapping works (roughly). 
> 
> ObjectMaxCardinality(2 child) expands to:
> 
> _:x rdf:type owl:Restriction
> _:x owl:maxCardinality "2"^^xsd:nonNegativeInteger
> _:x owl:onProperty child
> 
> ObjectMaxCardinality(2 child Person) expands to:
> 
> _:y rdf:type owl:Restriction
> _:y owl:maxCardinality "2"^^xsd:nonNegativeInteger
> _:y owl:onProperty child
> _:y owl11:onClass Person
> 
> Note especially that the first set of triples is a "subset" of the
> second set.

I think that this also introduces a problem when performing an inverse RDF
mapping. Imagine you stream in an RDF serialization of an OWL ontology in
order to map it into Functional Syntax. Assume further that at a certain
point in the input stream you have found the following three triples:

  _:y rdf:type owl:Restriction
  _:y owl:maxCardinality "2"^^xsd:nonNegativeInteger
  _:y owl:onProperty child

The problem is that you cannot tell for sure whether _:y denotes a "normal"
cardinality restriction, or a QCR. You will only know for sure after you
have scanned the /complete/ input stream, because only then you will know
whether there is an additional triple

  _:y owl11:onClass Person

or not. So you cannot start processing cardinality restrictions (and other
parts of the ontology depending on them) until the whole ontology has been
read in.

I'm not sure, but hasn't it been one of the design goals for the new RDF
mapping to have such kinds of problems eliminated? Esp., haven't there been
people (implementors) asking for better streaming possibilities compared to
what the OWL-1.0 RDF mapping provides? AFAICS, the problem demonstrated
above only occurs with the RDF syntax of cardinality restrictions (both
object and data). So if the WG regards this to be a real problem, then (as
Alan already proposed) having a set of new properties like

  owl11:maxQualifiedCardinality  

should suffice to solve this problem.


Cheers,
Michael

> 
> 
> The OWL 1.0 Full semantics says that the class extension of _:x is the
> set of objects that are related to at most two objects via the property
> extension of child.  A similar-style OWL 1.1 Full semantics would say
> that the class extension of _:y is the set of objects that are related
> to at most two objects that belong to the class extension of Person via
> the property extension of child.
> 
> However, the OWL 1.1 Full semantics would then also include the OWL 1.0
> Full semantics.  So, part of the meaning of the last four triples
> (actually the first three of these four, but that doesn't matter) in OWL
> 1.1 Full would be that the class extension of _:y would *as well* be the
> set of objects that are related to at most 2 objects via the property
> extension of child.
> 
> So, if o is in the class extension of _:y then it is related to at most
> two objects that belong to the class extension of Person via the
> property extension of child *and* it is related to at most two objects
> via the property extension of child.  It is impossible to have a max-QCR
> without this double meaning.
> 
> 
> 
> peter

--
Dipl.-Inform. Michael Schneider
FZI Forschungszentrum Informatik Karlsruhe
Abtl. Information Process Engineering (IPE)
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Email: Michael.Schneider@fzi.de
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Received on Thursday, 13 December 2007 08:52:01 GMT

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