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Re: Are properties from a context-constrained class inherited by subclasses?

From: Peter F. Patel-Schneider <pfps@research.bell-labs.com>
Date: Thu, 22 May 2003 03:21:46 -0400 (EDT)
Message-Id: <20030522.032146.123562125.pfps@research.bell-labs.com>
To: costello@mitre.org
Cc: www-rdf-interest@w3.org

From: "Roger L. Costello" <costello@mitre.org>
Subject: Are properties from a context-constrained class inherited by subclasses?
Date: Wed, 21 May 2003 17:05:10 -0400

> Hi Folks,
> 
> Suppose that I have this class heirarchy:
> 
>         River
>            |
>       Flueve
>           |
>        Blah
> 
> Suppose that the property, emptiesInto, has a domain of River:
> 
>      <owl:ObjectProperty rdf:ID="emptiesInto">
>            <rdfs:domain rdf:resource="#River"/>
>            <rdfs:range rdf:resource="#BodyOfWater"/>
>      </owl:ObjectProperty>
> 
> Suppose the Flueve constrains emptiesInto to have a range of #Sea:
> 
>      <owl:Class rdf:ID="Flueve">
>          <rdfs:subClassOf rdf:resource="#River"/>
>           <rdfs:subClassOf>
>                 <owl:Restriction>
>                         <owl:onProperty rdf:resource="#emptiesInto"/>
>                         <owl:allValuesFrom rdf:resource="#Sea"/>
>                 </owl:Restriction>
>           </rdfs:subClassOf>
>      </owl:Class>
> 
> Question: what is the range of emptiesInto when used in the Blah
> Class?   /Roger

Well, it is the case that all values of emptiesInto for instances of Blah
must belong to Sea, so one might say that Sea is *the* range of emptiesInto
for Blah.  However, it is also the case that all values of emptiesInto for
instances of Blah must belong to BodyOfWater, so one might say that
BodyOfWater is *the* range of emptiesInto for Blah.

I would, however, argue that the question is ill formed.  There is no one
range.  One might want to determine the minimal or most-constrained range,
but even this can be tricky, particulary in OWL.  

If one is being a bit imprecise it usually doesn't cause any problems to
refer to *the* range here, meaning the most-specific of all the ``told''
ranges for more-general classes, when there is one.

Peter F. Patel-Schneider
Bell Labs Research
Received on Thursday, 22 May 2003 03:22:05 GMT

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