owl:allValuesFrom inference

Question

Hi

I think I understand correctly owl:allValuesFrom and owl:someValuesFrom. More specifically I understand that an owl:allValuesFrom restriction on a property also applies to individuals that don't have a value for that property. What I don't quite understand is how the reasoner uses an owl:allValuesFrom in that case :

:hasHouse rdf:type owl:ObjectProperty ;          
          rdfs:range :House ;          
          rdfs:domain :Human .

:House rdf:type owl:Class .
:Human rdf:type owl:Class .

:Igloo rdf:type owl:Class ;
       rdfs:subClassOf :House .

:IglooInhabitants rdf:type owl:Class ;    
                  owl:equivalentClass [ rdf:type owl:Restriction ;
                                        owl:onProperty :hasHouse ;
                                        owl:allValuesFrom :Igloo
                                      ] ;
                  rdfs:subClassOf :Human .

The result of the inference is "Human equivalentClass owl:Thing". Why ? can somebody clarify with its own words the explanation of that inference given by Protégé :

IglooInhabitants subclassOf Human
hasHouse domain Human
IglooInhabitants equivalentTo hasHouse only Igloo

I would really like to express "Igloo inhabitants are all the humans that have an igloo as their house" (whether they have only igloos as their house or at least one igloo as their house doesn't really matter for the moment, I am still experimentating for the best solution). Does using universal quantifier makes sense in that case ? what would be the different modeling alternatives, and which one is the closest to what I want to express :

IglooInhabitants subClassOf Human and IglooInhabitants subClassOf hasHouse some Igloo
IglooInhabitants subClassOf Human and IglooInhabitants subClassOf hasHouse only Igloo
IglooInhabitants subClassOf Human and IglooInhabitants equivalentTo hasHouse some Igloo
IglooInhabitants subClassOf Human and IglooInhabitants equivalentTo hasHouse only Igloo (well, obviously this one doesn't work)
IglooInhabitants subClassOf hasHouse only Igloo
IglooInhabitants subClassOf hasHouse some Igloo
IglooInhabitants equivalentTo hasHouse only Igloo
IglooInhabitants equivalentTo hasHouse some Igloo
IglooInhabitants subClassOf Human and IglooInhabitants equivalentTo hasHouse only Igloo and hasHouse min 1

Thanks

Accepted Answer

The result of the inference is "Human equivalentClass owl:Thing". Why ?

The axiom IglooInhabitants equivalentTo hasHouse only Igloo implies that everything that does not have a house is an igloo inhabitant, and igloo inhabitants are human. Everything that does have a house, whatever it is, is a human too, because of axiom hasHouse domain Human. So everything is a human.

"Igloo inhabitants are all the humans that have an igloo as their house"

If you want to express this, you need at least to say that igloo inhabitants have some igloo. I suggest:

IglooInhabitant  subClassOf  hasHouse some Igloo

You can also change the subClassOf above into an equivalentWith, if this is what you want. Then it's up to you whether a person who has another house, not necessarily an igloo, should be classified as an igloo inhabitant or not. That is:

IglooInhabitant  equivalentWith  (hasHouse some Igloo and hasHouse only Igloo)

In any case, you must have a clear understanding of what an igloo inhabitant is before we can tell you how it should be modelled in OWL. You must also be clear about what hasHouse means. In your model, a house can only belong to a human, not to a company or a pixie. Too bad Santa's magical elves cannot own an igloo!

owl:allValuesFrom inference

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