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/* This file is part of the OWL API.
 * The contents of this file are subject to the LGPL License, Version 3.0.
 * Copyright 2014, The University of Manchester
 * 
 * This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.
 * This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
 * You should have received a copy of the GNU General Public License along with this program.  If not, see http://www.gnu.org/licenses/.
 *
 * Alternatively, the contents of this file may be used under the terms of the Apache License, Version 2.0 in which case, the provisions of the Apache License Version 2.0 are applicable instead of those above.
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at
 * http://www.apache.org/licenses/LICENSE-2.0
 * Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License. */
package org.semanticweb.owlapi.util;

import java.util.Set;

import javax.annotation.Nonnull;

import org.semanticweb.owlapi.model.OWLDataFactory;
import org.semanticweb.owlapi.model.OWLObjectProperty;
import org.semanticweb.owlapi.model.OWLObjectPropertyCharacteristicAxiom;
import org.semanticweb.owlapi.model.OWLObjectSomeValuesFrom;
import org.semanticweb.owlapi.reasoner.OWLReasoner;

/**
 * @author Matthew Horridge, The University Of Manchester, Bio-Health
 *         Informatics Group
 * @since 2.1.0
 */
public class InferredObjectPropertyCharacteristicAxiomGenerator
        extends
        InferredObjectPropertyAxiomGenerator {

    @Override
    protected void addAxioms(OWLObjectProperty entity, OWLReasoner reasoner,
            @Nonnull OWLDataFactory dataFactory,
            Set result) {
        addIfEntailed(dataFactory.getOWLFunctionalObjectPropertyAxiom(entity),
                reasoner, result);
        addIfEntailed(
                dataFactory.getOWLInverseFunctionalObjectPropertyAxiom(entity),
                reasoner, result);
        addIfEntailed(dataFactory.getOWLSymmetricObjectPropertyAxiom(entity),
                reasoner, result);
        addIfEntailed(dataFactory.getOWLAsymmetricObjectPropertyAxiom(entity),
                reasoner, result);
        addTransitiveAxiomIfEntailed(entity, reasoner, dataFactory, result);
        addIfEntailed(dataFactory.getOWLReflexiveObjectPropertyAxiom(entity),
                reasoner, result);
        addIfEntailed(dataFactory.getOWLIrreflexiveObjectPropertyAxiom(entity),
                reasoner, result);
    }

    protected static void addTransitiveAxiomIfEntailed(
            @Nonnull OWLObjectProperty property, OWLReasoner reasoner,
            OWLDataFactory dataFactory,
            Set result) {
        OWLObjectPropertyCharacteristicAxiom axiom = dataFactory
                .getOWLTransitiveObjectPropertyAxiom(property);
        if (reasoner.isEntailmentCheckingSupported(axiom.getAxiomType())
                && reasoner.isEntailed(axiom)) {
            if (!triviallyTransitiveCheck(property, reasoner, dataFactory)) {
                result.add(axiom);
            }
        }
    }

    /**
     * Test to see if a property is only vacuously transitive; i.e. if there
     * cannot be any three individuals a,b,c such that foo(a,b) and foo(b,c) -
     * e.g. if the domain and range of foo are disjoint. .
     * 
     * @param property
     *        property to test
     * @param reasoner
     *        reasoner to use for testing
     * @param df
     *        data factory
     * @return true if property is trivially transitive, or if entailment
     *         checking for OWLObjectPropertyAssertionAxioms is not supported.
     */
    private static boolean triviallyTransitiveCheck(
            @Nonnull OWLObjectProperty property, OWLReasoner reasoner,
            OWLDataFactory df) {
		// create R some (R some owl:Thing) class
		OWLObjectSomeValuesFrom chain = df.getOWLObjectSomeValuesFrom(property,
				df.getOWLObjectSomeValuesFrom(property, df.getOWLThing()));
		// if chain is unsatisfiable, then the property is trivially transitive
		return !reasoner.isSatisfiable(chain);
    }

    protected static void addIfEntailed(
            OWLObjectPropertyCharacteristicAxiom axiom, OWLReasoner reasoner,
            Set result) {
        if (reasoner.isEntailmentCheckingSupported(axiom.getAxiomType())
                && reasoner.isEntailed(axiom)) {
            result.add(axiom);
        }
    }

    @Override
    public String getLabel() {
        return "Object property characteristics";
    }
}