OWL negate object property

Question

I have a small toy ontology in protege and I want to represent that "a duck that is only white is an AlbinoDuck"

This is my ontology

I also created the property hasColor

I have the general class axiom for NormalDuck as Duck and (hasColor some Color) SubClassOf NormalDuck because if it's a Duck and it has any color then it's a NormalDuck (I don't care if Albino Ducks are also considered Normal)

Then for AlbinoDuck I have hasColor only White SubClassOf AlbinoDuck

Now, I have created two individuals:

• ThisIsNormalDuck with types Duck, hasColor some Black, hasColor some White. This represents a Black and white duck.
• ThisIsAlbinoDuck with types Duck and hasColor some White.

However, when I run the Reasoner the class NormalDuck is inferred for both individuals. What I expected was that ThisIsAlbinoDuck would be both Normal and Albino.

I have two questions about this:

• What I want to define is that AlbinoDucks can only have a single color and it has to be white. how can I do this in protege/owl language?

• What if I want to define "Something that is White and could have other colors but not brown"? (it could be White or White and Black)

Answer 1

There are 2 issues with your ontology:

1. hasColor only White SubClassOf AlbinoDuck means the hasColor only White set is a subset of the AlbinoDuck set. Thus it is possible to have individuals that belong to the AlbinoDuck set but the hasColor only White set. You need to use EquivalentTo rather than SubsetOf.

   Class: AlbinoDuck
      EquivalentTo:
      hasColor only White
      SubClassOf:
        Duck
   

2. Stating that ThisIsAlbinoDuck has type hasColor some White says that it has the color white, but is does not exclude the possibility that it also could have other colours. To force it not have other colors you should

(a) ensure that the only colors you can have are White, Black and Brown and

 Class: Color
   DisjointUnionOf:
     Black, Brown, White

(b) state that ThisIsAlbinoDuck does not have the colors Black and Brown.

  Types:
    Duck,
    not (hasColor some (Black or Brown)),
    hasColor some Color

The complete ontology looks as follows:

   ObjectProperty: hasColor

   Class: AlbinoDuck
      EquivalentTo:
      hasColor only White
      SubClassOf:
        Duck

   Class: Black
      SubClassOf:
        Color

   Class: Brown
      SubClassOf:
        Color

   Class: Color
      DisjointUnionOf:
         Black, Brown, White

   Class: Duck
      DisjointUnionOf:
      AlbinoDuck, NormalDuck

   Class: NormalDuck
      EquivalentTo:
        hasColor some (Black or Brown)
      SubClassOf:
        Duck

    Class: White
      SubClassOf:
        Color

   Individual: albinoDuck
      Types:
        Duck,
        not (hasColor some (Black or Brown)),
        hasColor some Color

    Individual: normalDuck
       Types:
       Duck,
         (hasColor some Black)
         and (hasColor some White)