I am new to Protégé so I have a very basic question.
I have the classes Child and Parent. Child has the subclass Girl.
child1 has the type Girl, child2 has the type Child and anna and peter have both the type Parent. In addition, there are the relations anna isParentOf child1 and peter isParentOf child2 with no further characteristics.
Now I want to define the class ParentOfGirl so that it is equivalent to Parent and isParentOf only Girl. I would expect that the reasoner infers that anna has this new type, but it does not.
I added the Inverse functional property to isParentOf because a parent can have more than one child. If I then add also Symmetric to the relation I get that anna has the type ParentOfGirl, but I do not want to have isParentOf to be symmetric.
If I look at the semantics of the above without symmetry, I see this:
ParentOfGirl ≡ {anna, peter} ⋂ { x ∊ owl:Thing | if ∀y (x, y) ∊ isParentOf then y ∊ Girl}
child1 ∊ Child and child1 ∊ Girl
isParentOf ≡ {(anna, child1), (peter, child2)}
Then child1 is the only individual of type Child in relation with anna and it has also the type Girl. It seems to me that the reasoner can look at the relations only from right to left in this case because if isParentOf is symmetric, it deduces anna. Furthermore, I would expect that peter would also be in ParentOfGirl if it was not in the relation with child2. But this also does not happen.
Why does the reasoner (Pellet or HermiT) does not see that anna is a ParentOfGirl?
@AKSW is correct in the comment. The reasoner cannot tell if a parent has only female children. You need to assert this feature, for example by adding a type to the individual.
In this case, this assertion would be equivalent to the inference you seek, though - so it's not a really good workaround.
If you change the forall to some, you will be able to find parents of at least one girl. This is a superclass of your target class, and might help your application along.