I need to get All direct superclasses of one class from the ontology, and I need just named classes, not those gotten from the equivalent expression with 'AllValuesFrom' restriction. I tried with the code below, it works for some ontologies that I create but others downloaded from the web (people ontology - pizza ontology) it doesn't work.
public void motherclasses_Of_One_class() {
for (OWLClass clss : ontology.getClassesInSignature())
{
if(reasoner.getSuperClasses(clss, true).getFlattened().size()>1) // if the class has more than one mother class
{// System.out.println(" \n ---------------- : \n");
System.out.println("\n class "+clss.getIRI().getFragment()+" has more than one mother classes : \n");
for(OWLClass parent: reasoner.getSuperClasses(clss, true).getFlattened())
System.out.println(parent.getIRI().getFragment());
}
}
}
I tried with this version of code too, the same result as the first version :
NodeSet superclasses = reasoner.getSuperClasses(clss, true);
for (org.semanticweb.owlapi.reasoner.Node parentOWLNode: superclasses) {
OWLClassExpression parent = parentOWLNode.getRepresentativeElement();
System.out.println(parent.getClassesInSignature());.out.println(parent.getClassesInSignature());
}
the problem with downloaded ontologies, that it returns wrong superclasses for a class. I check the . OWL file, then the ontology through protégé, I can't find from when the problem comes. Please find below a wrong case to understand more what I mean.
In the example, 'cat_owner' class has just one mother 'person' class. As you can see, pet_owner and cat_liker classes are at the same hierarchical level as 'cat_owner' class, they can never be mothers for 'cat_owner' class, and more than that in the description of 'cat_owner' class there is just one superclass 'person' class... but in the program output I get them as superclass 'person' class... but in the program output I get them as superclasses of 'cat_owner' class when 'person' class is absent form the list. I can't understand why... this is the output: from the list. I can't understand why...
Please if you have any idea that may help, I would be grateful. Thank you
Hasna, hi.
The behaviour you are observing is because (guessing from the variable names in your code fragment) you are accessing the ontology through a reasoner. This means that you are getting inferred statements in addition to the explicit statements you see when you edit the ontology file. In your particular example, note these axioms in the People Ontology:
Class: people:cat_liker EquivalentTo: people:person and (people:likes some people:cat)
ObjectProperty: people:has_pet SubPropertyOf: people:likes
Class: people:cat_owner EquivalentTo: people:person and (people:has_pet some people:cat)
which force any instance of cat_ower to be by necessity also an instance of cat_liker. In other words, the reasoner can prove that cat_ower is a subclass of cat_liker, so the OWL API also returns this result. Similarly:
Class: people:pet_owner EquivalentTo: people:person and (people:has_pet some people:animal)
Class: people:cat SubClassOf: people:animal
forces any instance of cat_ower to be by necessity also an instance of pet_owner, so pet_owner is also added to the superclasses of cat_owner.
If you want to get explicit subClassOf statements only, use the subClassAxiomsForSubClass() property of the OWLOntology object, not a reasoner object. Hope this helps, Stasinos
Here is a relevant answer returned by Google:
https://stackoverflow.com/questions/17611477/getting-superclasses-in-imported-owl-ontology
And here is the relevant reference to the OWL API documentation:
http://owlcs.github.io/owlapi/apidocs_4/org/semanticweb/owlapi/reasoner/OWLReasoner.html#getSuperClasses-org.semanticweb.owlapi.model.OWLClassExpression-boolean-
This answer might slightly be off topic but it might nevertheless help those who were brought here by a search algorithm and are not dependent on owlapi (i.e. java):
with the owlready python library one can easily get the superclasses via the `.is_a` attribute (datatype list) of any subclass of `owlready.Thing`. See https://owlready2.readthedocs.io/en/latest/class.html?highlight=is_a#creating-and-managing-subclasses
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