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

From: Ivan Herman <ivan@w3.org>
Date: Thu, 03 Jul 2008 17:34:10 +0200
Message-ID: <486CF172.8060108@w3.org>
To: Ivan Herman <ivan@w3.org>, public-powderwg@w3.org
I must admit I did not remember that nuance, ie, that hasValue 
guarantees the existence of one triple. You are absolutely right.

Bottomline: I hereby withdraw that comment...

Ivan

Stasinos Konstantopoulos wrote:
> 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
> 

-- 

Ivan Herman, W3C Semantic Web Activity Lead
Home: http://www.w3.org/People/Ivan/
PGP Key: http://www.ivan-herman.net/pgpkey.html
FOAF: http://www.ivan-herman.net/foaf.rdf

Received on Thursday, 3 July 2008 15:34:46 GMT

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