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Re: Inferring that a Camera is a SLR?

From: David Jacobs <djacobs@mitre.org>
Date: Fri, 18 Apr 2003 08:49:03 -1000
Message-ID: <3EA0489F.40505@mitre.org>
To: "Roger L. Costello" <costello@mitre.org>
CC: www-rdf-interest@w3.org

Roger,

To get the inference you want you would need to assert that all Cameras 
with through the lens viewfinders are SLRs (which is not true 
obviously).  But if you wanted to make that assertion you could define 
the SLR class as:

<owl:Class rdf:ID="SLR">
  <owl:intersectionOf rdf:parsetype="Collection">
    <owl:Class rdf:about="#Camera">
    <owl:Restriction>
      <owl:onProperty rdf:resource="#viewFinder"/>
      <owl:hasValue rdf:resource="#ThroughTheLens"/>
    </owl:Restriction>
  </owl:intersectionOf>
</owl:Class>

With this definition you could make the inference you wanted.

Cheers,
David

Roger L. Costello wrote:

>Hi Folks,
>
>I am a bit stuck on an inference.  I want to be able to infer that this
>document is talking about a SLR:
>
><Camera>
>     <viewFinder rdf:resource="http://www.camera.org#ThroughTheLens"/>
>     ...
></Camera>
>
>Here is the piece of knowledge that I am trying to use to make the
>inference: 
>
>    "Only SLRs have a ThroughTheLens viewFinder"
>
>When I defined SLR I restricted the value of viewFinder to
>'ThroughTheLens', as shown here:
>
>     <owl:Class rdf:ID="SLR">
>          <rdfs:subClassOf rdf:resource="#Camera"/>
>          <rdfs:subClassOf>
>              <owl:Restriction>
>                   <owl:onProperty rdf:resource="#viewFinder"/>
>                   <owl:hasValue rdf:resource="#ThroughTheLens"/>
>              </owl:Restriction>
>          </rdfs:subClassOf>
>     </owl:Class>
>
>And when I defined viewFinder I stated that it is a FunctionalProperty
>and all Cameras have a viewFinder:
>
>     <owl:ObjectProperty rdf:ID="viewFinder">
>          <rdf:type rdf:resource="&owl;#FunctionalProperty"/>
>          <rdfs:domain rdf:resource="#Camera"/>
>          <rdfs:range rdf:resource="#Viewer"/>
>     </owl:ObjectProperty>
>
>Initially, I thought that these two OWL statements were sufficient to
>allow me to infer for the above instance that the Camera is a SLR.  I
>now believe, however, that it only allows me to infer that it "may" be a
>SLR.  True?  What do I need to allow me to infer that the Camera "must"
>be a SLR?  /Roger
>
>  
>
Received on Friday, 18 April 2003 14:49:20 GMT

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