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[protege-owl] How to detect undefined references in rdf:resource

Thomas Russ tar at ISI.EDU
Mon Jan 25 11:33:14 PST 2010

On Jan 25, 2010, at 10:52 AM, Buns wrote:

> Ok,
> you mean for example having a Sign class
> default:Sign
>       a       owl:Class .
> and a Street class
> default:Street
>       a       owl:Class .
> with an object property hasSign
> default:hasSign
>       a       owl:ObjectProperty ;
>       rdfs:domain default:Street ;
>       rdfs:range default:Sign .
> and having only one individual:
> default:Street_5
>       a       default:Street ;
>       default:hasSign default:Sign_4 .
> Sign_4 ist not defined within the ontology ... but the reasoner can  
> infer that Sign_4 really is a Sign because of the range of the  
> object property hasSign and therefore will not classify it as an  
> protege:ExternalResource?
> If the reasoner acts like this it ist fine. The only thing I need  
> is having a possibility to check for unresolved references like  
> Sign_4, which actually neighter is defined within this ontology nor  
> in explicit imported ones. Do you see a chance for me to complete  
> this task with owl/pellet/sqwrl?

Actually, Sign_4 is defined in this ontology.  It is explicitly  
mentioned, and in a context in which it is clear that it must be an  
Individual.  The only way you would get something that doesn't have  
some implicit type is to have a mention of it where there is no  
context that allows figuring out if it is a class, property or  
individual.  So you would need something like

   default:Something .

with no other information.  Just about anything else you might say  
about it would give some clue as to what sort of object it would need  
to be, and then it would be recognized and treated as such an object.

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