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Re: Case for Reinstatement of Qualified Cardinality Restrictions

From: Peter F. Patel-Schneider <pfps@research.bell-labs.com>
Date: Thu, 24 Apr 2003 19:26:11 -0400 (EDT)
Message-Id: <20030424.192611.01431429.pfps@research.bell-labs.com>
To: heflin@cse.lehigh.edu
Cc: www-webont-wg@w3.org

From: Jeff Heflin <heflin@cse.lehigh.edu>
Subject: Re: Case for Reinstatement of Qualified Cardinality Restrictions
Date: Thu, 24 Apr 2003 15:46:04 -0400

> Sorry, this issue keeps nagging at me...
> 
> I looked at Sect. 5 of S&AS (RDF-compatible semantics) and it seems that
> it gives semantics to Restriction resources that have some combination
> of cardinality, someValuesFrom and allValuesFrom properties, such as in
> the example below.
> 
> <owl:Restriction>
>   <owl:onProperty rdf:resource="&eg;hasDigit"/>
>   <owl:cardinality rdf:datatype="&xsd;int">5</owl:cardinality>
>   <owl:allValuesFrom rdf:resource="&eg;Digit" />
>   <owl:someValuesFrom rdf:resource="&eg;Finger" />
> </owl:Restriction>
> 
> Furthermore, it looks like the semantics would be the same as if you had
> an intersection of:
> 
> <owl:Restriction>
>   <owl:onProperty rdf:resource="&eg;hasDigit"/>
>   <owl:cardinality rdf:datatype="&xsd;int">5</owl:cardinality>
> </owl:Restriction>
> 
> <owl:Restriction>
>   <owl:onProperty rdf:resource="&eg;hasDigit"/>
>   <owl:allValuesFrom rdf:resource="&eg;Digit" />
> </owl:Restriction>
> 
> <owl:Restriction>
>   <owl:onProperty rdf:resource="&eg;hasDigit"/>
>   <owl:someValuesFrom rdf:resource="&eg;Finger" />
> </owl:Restriction>

No.  It is different.  The first implies that the extension of the three
just above are all the same.

> The reason is that in the section called "Conditions on OWL
> restrictions" the semantics for each of these types of restrictions only
> depends on having two triples (onProperty and something else) with the
> same subject, and these conditions are met in the "jumbo restriction"
> above.
> 
> However, this seems to contradict Section 4 (Mapping to RDF Graphs)
> which does not provide a translation into the "jumbo restriction" and
> therefore implies that it doesn't have semantics, and also isn't even
> valid syntax.

No, all that this indicates is that the first is not in OWL DL.

> This is very confusing. I thought the mapping to RDF defined the RDF
> syntax, but that doesn't seem to be the case.  Does it just define the
> syntax for OWL DL, and not OWL Full? 

The mapping to RDF defines the syntax for OWL DL and OWL Lite.

> Even if this was the case, it would
> seem that the RDF combatible semantics and the abstract semantics
> disagree on what constitutes an OWL DL graph (take this Restriction case
> as an example). Is it the case that the RDF compatible semantics only
> apply to some subset of RDF graphs as determined by the transformation
> in Section 4?

The RDF-compatible smenatics applies for all RDF graphs.

> Help, I think my brain is about to explode. :-(

Welcome to the wonderful world of triples.  :-)

> Jeff

peter
Received on Thursday, 24 April 2003 19:26:24 GMT

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