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This is my ontology created with protege 5 .

If i make cl1 and cl2 disjoint, then the ontology is being inconsistent , but if i uncheck is_friend_of reflexive , the ontology is not inconsistent any more . whats wrong with my ontology ?

I want only cl1 class individuals have is_friend_of property.

Stanislav Kralin
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alex
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1 Answers1

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Reflexivity of :is_friend_of is essential for inconsistency.

Take a look at Reasoner > Inconsistent ontology explanation :

Inconsistency explanation

I'll try to translate this explanation into (poor) English:

  1. Since :is_friend_of is reflexive, then :c2_inst :is_friend_of :c2_inst.
  2. Since the domain of :is_friend_of is :cl1, then c2_inst rdf:type :cl1.
  3. Also, c2_inst rdf:type :cl2.
  4. But :cl1 and :cl2 are disjoint — contradiction.

In fact, the domain of every reflexive property is owl:Thing.

As a workaround, you could uncheck reflexivity of is_friend_of and define :cl1 in this way:

Class: cl1
    EquivalentTo: 
        is_friend_of some owl:Thing,
        is_friend_of some  Self
Stanislav Kralin
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  • Thanks, you said `In fact, the domain of every reflexive property is owl:Thing` . why ? why i cant limit a reflexive property domain to only one defined class as i do for other properties? – alex Jun 30 '17 at 04:40
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    The reflexivity is a global property, it affects all individuals. If you want a local reflexivity, use `Self` as suggested in the answer. – Dmitry Tsarkov Jun 30 '17 at 06:20
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    @alex, see [this thread](https://mailman.stanford.edu/pipermail/protege-owl/2011-June/016877.html). Additionally, please use `has_friend` or something like instead of `is_friend_of`, it will be easier to understand. BTW, there are [inverse object properties](https://www.w3.org/TR/2012/REC-owl2-syntax-20121211/#Inverse_Object_Properties_2). – Stanislav Kralin Jun 30 '17 at 07:53
  • @alex Shouldn't `is_friend_of` be symmetric instead of reflexive? – UninformedUser Jul 01 '17 at 19:29