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Re: Comment on POWDER WDR, 2008-06-30: exact translation of descriptorset into POWDER-S

From: Stasinos Konstantopoulos <konstant@iit.demokritos.gr>
Date: Thu, 3 Jul 2008 18:20:26 +0300
To: Ivan Herman <ivan@w3.org>
Cc: public-powderwg@w3.org
Message-ID: <20080703152026.GC3791@iit.demokritos.gr>
Ivan, hi again.

On Thu Jul  3 15:36:00 2008 Ivan Herman said:

> Comment on http://www.w3.org/TR/2008/WD-powder-dr-20080630/
>
> Looking at examples 2.2 and 2.3 and the way it is translated into  
> POWDER-S: the translation is an intersection of restrictions:
>
> <owl:Class rdf:nodeID="descriptorset_1">
> 27      <owl:intersectionOf rdf:parseType="Collection">
> 28        <owl:Restriction>
> 29          <owl:onProperty rdf:resource="http://example.org/vocab#color" />
> 30          <owl:hasValue>red</owl:hasValue>
> 31        </owl:Restriction>
> 32        <owl:Restriction>
> 33          <owl:onProperty rdf:resource="http://example.org/vocab#shape" />
> 34          <owl:hasValue>square</owl:hasValue>
> 35        </owl:Restriction>
> 36      </owl:intersectionOf>
> 37      <dc:description>Everything on example.org is red and  
> square</dc:description>
> 38      <foaf:depiction rdf:resource="http://example.org/icon.png" />
> 39    </owl:Class>
>
>
> what this means, strictly speaking, is that if I take an instance of  
> that class, the 'color' or 'shape' properties will take that specified  
> values _if they are applied_. However, it does _not_ say that this  
> property _is_ applied on those instances. If the intention of the spec  
> is to say 'this and this property _is_ applied and it has this and this  
> value', then an extra cardinality restriction for each of those  
> properties might be necessary... It is up to the group to decide what  
> the intention is, though.

This would be the case with owl:allValuesFrom. owl:hasValue guarantees
the existence of at least one triple relating the resource with the
value:

  hasValue allows us to specify classes based on the existence of
  particular property values. Hence, an individual will be a member of
  such a class whenever at least one of its property values is equal to
  the hasValue resource.

  http://www.w3.org/TR/2004/REC-owl-guide-20040210/#hasValue

Empirical verification: the attached exIvan.owl returns:

Query Results (11 answers):
r                 | y
=========================================
ontology:tag      | "tag2"^^xsd:string
ontology:tag      | "my tag3"^^xsd:string
ontology:tag      | "tag1"^^xsd:string
ontology:cp-1.1   | "1"^^xsd:int
ontology:cp-1.2   | "1"^^xsd:int
rdf:type          | ontology:Class1
rdf:type          | owl:Thing
rdf:type          | ontology:Resource
rdf:type          | ontology:Class2
owl:sameAs        | ontology:website2
owl:differentFrom | ontology:website1

when queried

  SELECT ?r ?y WHERE { <http://www.test.org/ontology.owl#website2> ?r ?y }

cheers,
s


Received on Thursday, 3 July 2008 15:21:09 GMT

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