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HermiT is reasoner for ontologies written using the Web Ontology Language (OWL). Given an OWL file, HermiT can determine whether or not the ontology is consistent, identify subsumption relationships between classes, and much more. This is the maven build of HermiT and is designed for people who wish to use HermiT from within the OWL API. It is now versioned in the main HermiT version repository, although not officially supported by the HermiT developers. The version number of this package is a composite of the HermiT version and a value representing the OWLAPI release it is compatible with. Note that the group id for the upstream HermiT is com.hermit-reasoner, while this fork is released under net.sourceforge.owlapi. This fork exists to allow HermiT users to use newer OWLAPI versions than the ones supported by the original HermiT codebase. This package includes the Jautomata library (http://jautomata.sourceforge.net/), and builds with it directly. This library appears to be no longer under active development, and so a "fork" seems appropriate. No development is intended or anticipated on this code base.

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/*______________________________________________________________________________
 * 
 * Copyright 2005 Arnaud Bailly - NORSYS/LIFL
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * (1) Redistributions of source code must retain the above copyright
 *     notice, this list of conditions and the following disclaimer.
 *
 * (2) Redistributions in binary form must reproduce the above copyright
 *     notice, this list of conditions and the following disclaimer in
 *     the documentation and/or other materials provided with the
 *     distribution.
 *
 * (3) The name of the author may not be used to endorse or promote
 *     products derived from this software without specific prior
 *     written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT,
 * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
 *  SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
 * OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 * Created on 20 fevr. 2005
 *
 */
package rationals.properties;

import java.util.HashSet;
import java.util.Iterator;
import java.util.Set;

import rationals.Automaton;
import rationals.Couple;
import rationals.State;
import rationals.Transition;

/**
 * This method computes the (strong) bisimulation relation between two states.
 * 
 * @author nono
 * @version $Id: Bisimulation.java 2 2006-08-24 14:41:48Z oqube $
 */
public class Bisimulation implements Relation {

    private Automaton a1;

    private Automaton a2;

    private Set exp;

    /**
     * Constructor with two automataon.
     * This constructor effectively calls {@link #setAutomata(Automaton,Automaton)}.
     * 
     * @param automaton automaton
     * @param automaton2 automaton2
     */
    public Bisimulation(Automaton automaton, Automaton automaton2) {
        setAutomata(automaton,automaton2);
    }

    /**
     * Argument-less constructor.
     * Note that this implies the method {@link #setAutomata(Automaton,Automaton)} 
     * must be called before using this relation.
     */
    public Bisimulation() {
    }

    @Override
    public void setAutomata(Automaton a1, Automaton a2) {
        this.a1 = a1;
        this.a2 = a2;
        this.exp = new HashSet<>();
    }

    @Override
    public boolean equivalence(State q0a, State q0b) {
        Couple cpl = new Couple(q0a, q0b);
        /* check states are unknown */
        if (exp.contains(cpl))
            return true;
        exp.add(cpl);
        /* iterate over all transitions */
        Set tas = a1.delta(q0a);
        Set tbs = a2.delta(q0b);
        Iterator it = tas.iterator();
        while (it.hasNext()) {
            Transition tr = it.next();
            State ea = tr.end();
            /* check transition exists in b */
            Set tbsl = a2.delta(q0b, tr.label());
            if (tbsl.isEmpty())
                return false;
            Iterator trb = tbsl.iterator();
            while (trb.hasNext()) {
                Transition tb = trb.next();
                /* mark transition as visited */
                tbs.remove(tb);
                State eb = tb.end();
                if (!equivalence(ea, eb) && !trb.hasNext())
                    return false;
            }
        }
        /* checks all transitions from b has been visited */
        if (!tbs.isEmpty()) {
            exp.remove(cpl);
            return false;
        }
        /* OK */
        return true;
    }

    @Override
    public boolean equivalence(Set nsa, Set nsb) {
       for(Iterator i = nsa.iterator();i.hasNext();) {
           State sa = i.next();
           for(Iterator j = nsb.iterator();j.hasNext();) {
               State sb = j.next();
               if(!equivalence(sa,sb))
                   return false;
           }
       }
       return true;
    }
}