owlexplanation with Hermit reasoner

Question

I am trying to use Hermit Reasoner to check consistency. Hermit reasoner by default does not provide any justification/explanations for the inconsistencies.

EDITED VERSION:: I'm currently trying with OWLReasoner, but still it which throws an error.

 import java.util.Set;

import org.semanticweb.HermiT.Reasoner;
import org.semanticweb.owl.explanation.api.Explanation;
import org.semanticweb.owl.explanation.api.ExplanationGeneratorFactory;
import org.semanticweb.owl.explanation.api.ExplanationManager;
import org.semanticweb.owl.explanation.impl.blackbox.checker.InconsistentOntologyExplanationGeneratorFactory;
import org.semanticweb.owlapi.apibinding.OWLManager;
import org.semanticweb.owlapi.model.IRI;
import org.semanticweb.owlapi.model.OWLAxiom;
import org.semanticweb.owlapi.model.OWLClass;
import org.semanticweb.owlapi.model.OWLOntology;
import org.semanticweb.owlapi.model.OWLOntologyManager;
import org.semanticweb.owlapi.reasoner.Node;
import org.semanticweb.owlapi.reasoner.OWLReasoner;
import org.semanticweb.owl.explanation.api.ExplanationGenerator;
import org.semanticweb.owlapi.model.OWLDataFactory;
import org.semanticweb.owlapi.model.OWLNamedIndividual;
import org.semanticweb.owlapi.model.OWLOntologyCreationException;
import org.semanticweb.owlapi.reasoner.OWLReasonerFactory;

public class ConsistencyChecker {

    public static void main(String[] args) throws Exception {
    OWLOntologyManager m=OWLManager.createOWLOntologyManager();

   OWLOntology o=m.loadOntologyFromOntologyDocument(IRI.create("http://www.cs.ox.ac.uk/isg/ontologies/UID/00793.owl"));

      // Reasoner hermit=new Reasoner(o);
        OWLReasoner owlreasoner=new Reasoner.ReasonerFactory().createReasoner(o);
        System.out.println(owlreasoner.isConsistent());

      //System.out.println(hermit.isConsistent());

        //---------------------------- Copied from example--------- 
        OWLDataFactory df = m.getOWLDataFactory();
        OWLClass testClass = df.getOWLClass(IRI.create("urn:test#testclass"));
        m.addAxiom(o, df.getOWLSubClassOfAxiom(testClass, df.getOWLNothing()));
        OWLNamedIndividual individual = df.getOWLNamedIndividual(IRI
                .create("urn:test#testindividual"));
        m.addAxiom(o, df.getOWLClassAssertionAxiom(testClass, individual));

        //----------------------------------------------------------

        Node<OWLClass> unsatisfiableClasses = owlreasoner.getUnsatisfiableClasses();
        //Node<OWLClass> unsatisfiableClasses = hermit.getUnsatisfiableClasses();
        for (OWLClass owlClass : unsatisfiableClasses) {
            System.out.println(owlClass.getIRI());
        }
        //-----------------------------
        ExplanationGeneratorFactory<OWLAxiom> genFac = ExplanationManager.createExplanationGeneratorFactory((OWLReasonerFactory) owlreasoner);
        ExplanationGenerator<OWLAxiom> gen = genFac.createExplanationGenerator(o);

        //-------------------------

        InconsistentOntologyExplanationGeneratorFactory igf = new InconsistentOntologyExplanationGeneratorFactory((OWLReasonerFactory) owlreasoner, 10000);
        //InconsistentOntologyExplanationGeneratorFactory igf = new InconsistentOntologyExplanationGeneratorFactory((OWLReasonerFactory) hermit, 10000);
        ExplanationGenerator<OWLAxiom> generator = igf.createExplanationGenerator(o);

        OWLAxiom entailment = df.getOWLClassAssertionAxiom(df.getOWLNothing(),
                individual);

        //-------------
        Set<Explanation<OWLAxiom>> expl = gen.getExplanations(entailment, 5);
        //------------

        System.out.println("Explanation "
                + generator.getExplanations(entailment, 5));
    }
}

The output is

true
http://www.w3.org/2002/07/owl#Nothing
http://www.co-ode.org/ontologies/pizza/pizza.owl#CheeseyVegetableTopping
http://www.co-ode.org/ontologies/pizza/pizza.owl#IceCream
Exception in thread "main" java.lang.ClassCastException: org.semanticweb.HermiT.Reasoner cannot be cast to org.semanticweb.owlapi.reasoner.OWLReasonerFactory
    at ConsistencyChecker.main(ConsistencyChecker.java:82)

Any help in integrating owlexplanation api [1] with the Hermit Reasoner/OWLReasoner would be appreciated.

[1]https://github.com/matthewhorridge/owlexplanation

Answer 1

//package org.semanticweb.HermiT.examples;

import java.util.Set;

import org.semanticweb.HermiT.Configuration;
import org.semanticweb.HermiT.Reasoner;
import org.semanticweb.HermiT.Reasoner.ReasonerFactory;
import org.semanticweb.owlapi.apibinding.OWLManager;
import org.semanticweb.owlapi.model.IRI;
import org.semanticweb.owlapi.model.OWLAxiom;
import org.semanticweb.owlapi.model.OWLClass;
import org.semanticweb.owlapi.model.OWLDataFactory;
import org.semanticweb.owlapi.model.OWLOntology;
import org.semanticweb.owlapi.model.OWLOntologyManager;
import org.semanticweb.owlapi.reasoner.OWLReasoner;

import com.clarkparsia.owlapi.explanation.BlackBoxExplanation;
import com.clarkparsia.owlapi.explanation.HSTExplanationGenerator;

public class Explanations {

    public static void main(String[] args) throws Exception {
        // First, we create an OWLOntologyManager object. The manager will load and 
        // save ontologies. 
        OWLOntologyManager manager=OWLManager.createOWLOntologyManager();
        // We will create several things, so we save an instance of the data factory
        OWLDataFactory dataFactory=manager.getOWLDataFactory();
        // Now, we create the file from which the ontology will be loaded. 
        // Here the ontology is stored in a file locally in the ontologies subfolder
        // of the examples folder.
        //File inputOntologyFile = new File("examples/ontologies/pizza.owl");
        // We use the OWL API to load the ontology. 
        //OWLOntology ontology=manager.loadOntologyFromOntologyDocument(inputOntologyFile);
        // We use the OWL API to load the Pizza ontology.
        OWLOntology ontology=manager.loadOntologyFromOntologyDocument(IRI.create("http://www.cs.ox.ac.uk/isg/ontologies/UID/00793.owl"));

        // Lets make things worth and turn Pizza into an inconsistent ontology by asserting that the 
        // unsatisfiable icecream class has some instance. 
        // First, create an instance of the OWLClass object for the unsatisfiable  icecream class.

        IRI icecreamIRI=IRI.create("http://www.co-ode.org/ontologies/pizza/pizza.owl#IceCream");
        OWLClass icecream=dataFactory.getOWLClass(icecreamIRI);

        // Now we can start and create the reasoner. Since explanation is not natively supported by 
        // HermiT and is realised in the OWL API, we need to instantiate HermiT 
        // as an OWLReasoner. This is done via a ReasonerFactory object. 
        ReasonerFactory factory = new ReasonerFactory();
        // We don't want HermiT to thrown an exception for inconsistent ontologies because then we 
        // can't explain the inconsistency. This can be controlled via a configuration setting.  
        Configuration configuration=new Configuration();
        configuration.throwInconsistentOntologyException=false;
        // The factory can now be used to obtain an instance of HermiT as an OWLReasoner. 
        OWLReasoner reasoner=factory.createReasoner(ontology, configuration);
        // Let us confirm that icecream is indeed unsatisfiable:
        System.out.println("Is icecream satisfiable? "+reasoner.isSatisfiable(icecream)); 
        System.out.println("Computing explanations...");
        // Now we instantiate the explanation classes
        BlackBoxExplanation exp=new BlackBoxExplanation(ontology, factory, reasoner);
        HSTExplanationGenerator multExplanator=new HSTExplanationGenerator(exp);
        // Now we can get explanations for the unsatisfiability. 
        Set<Set<OWLAxiom>> explanations=multExplanator.getExplanations(icecream);
        // Let us print them. Each explanation is one possible set of axioms that cause the 
        // unsatisfiability. 
        for (Set<OWLAxiom> explanation : explanations) {
            System.out.println("------------------");
            System.out.println("Axioms causing the unsatisfiability: ");
            for (OWLAxiom causingAxiom : explanation) {
                System.out.println(causingAxiom);
            }
            System.out.println("------------------");
        }
        // Let us make the ontology inconsistent to also get explanations for an 
        // inconsistency, which is slightly more involved since we dynamically 
        // have to change the factory constructor; otherwise, we can't suppress 
        // the inconsistent ontology exceptions that the OWL API requires a 
        // reasoner to throw.  
        // Let's start by adding a dummy individual to the unsatisfiable Icecream class. 
        // This will cause an inconsistency. 
        OWLAxiom ax=dataFactory.getOWLClassAssertionAxiom(icecream, dataFactory.getOWLNamedIndividual(IRI.create("http://www.co-ode.org/ontologies/pizza/pizza.owl#dummyIndividual")));
        manager.addAxiom(ontology, ax);
        // Let us confirm that the ontology is inconsistent
        reasoner=factory.createReasoner(ontology, configuration);
        System.out.println("Is the changed ontology consistent? "+reasoner.isConsistent());
        // Ok, here we go. Let's see why the ontology is inconsistent. 
        System.out.println("Computing explanations for the inconsistency...");
        factory=new Reasoner.ReasonerFactory() {
            protected OWLReasoner createHermiTOWLReasoner(org.semanticweb.HermiT.Configuration configuration,OWLOntology ontology) {
                // don't throw an exception since otherwise we cannot compte explanations 
                configuration.throwInconsistentOntologyException=false;
                return new Reasoner(configuration,ontology);
            }  
        };
        exp=new BlackBoxExplanation(ontology, factory, reasoner);
        multExplanator=new HSTExplanationGenerator(exp);
        // Now we can get explanations for the inconsistency 
        explanations=multExplanator.getExplanations(dataFactory.getOWLThing());
        // Let us print them. Each explanation is one possible set of axioms that cause the 
        // unsatisfiability. 
        for (Set<OWLAxiom> explanation : explanations) {
            System.out.println("------------------");
            System.out.println("Axioms causing the inconsistency: ");
            for (OWLAxiom causingAxiom : explanation) {
                System.out.println(causingAxiom);
            }
            System.out.println("------------------");
        }
    }
}

Answer 2

The error is because you're casting an OWLReasoner to an OWLReasonerFactory.

The OWLReasonerFactory for HermiT is the one you've used a few lines above:

new Reasoner.ReasonerFactory()