rationals.properties.Simulation Maven / Gradle / Ivy
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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 21 juin 2005
*
*/
package rationals.properties;
import java.util.HashSet;
import java.util.Iterator;
import java.util.List;
import java.util.Set;
import rationals.Automaton;
import rationals.Couple;
import rationals.State;
import rationals.Transition;
/**
* This class implements (strong) simulation equivalence between
* two automata.
*
* Given two automata A=(Qa,q0a,Ta,Sa,deltaA) and B=(Qb,q0b,Tb,Sb,deltaB),
* a simulation S of A by B is a relation in Qa x Qb
* s.t., whenever (qa,qb) \in S,
*
* - for each
(qa,a,qa') \in deltaA, exists (qb,a,qb')\in deltaB
* and (qa',qb') \in S,
*
* B is a simulation of A iff q0b ~ q0a.
*
* Note that in general, a simulation is not symetric. A symetric
* simulation is of course a bisimulation.
*
* @author nono
* @version $Id: Simulation.java 2 2006-08-24 14:41:48Z oqube $
* @see rationals.properties.Bisimulation
*/
public class Simulation 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
* @param automaton2
*/
public Simulation(Automaton automaton, Automaton automaton2) {
setAutomata(automaton,automaton2);
}
/*
* (non-Javadoc)
*
* @see rationals.tests.Relation#setAutomata(rationals.Automaton,
* rationals.Automaton)
*/
public void setAutomata(Automaton a1, Automaton a2) {
this.a1 = a1;
this.a2 = a2;
this.exp = new HashSet();
}
public Simulation() {}
/**
* Checks that all combination of states from nsa and nsb
* are bisimilar.
*
*/
public boolean equivalence(Set nsa, Set nsb) {
for(Iterator i = nsa.iterator();i.hasNext();) {
State sa = (State)i.next();
for(Iterator j = nsb.iterator();j.hasNext();) {
State sb = (State)j.next();
if(!equivalence(sa,sb))
return false;
}
}
return true;
}
/*
* (non-Javadoc)
*
* @see rationals.tests.Relation#equivalence(rationals.State,
* rationals.State)
*/
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 = (Transition) 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 = (Transition) trb.next();
/* mark transition as visited */
tbs.remove(tb);
State eb = tb.end();
if (!equivalence(ea, eb) && !trb.hasNext())
return false;
}
}
/* OK */
return true;
}
/* (non-Javadoc)
* @see rationals.properties.Relation#getErrorTrace()
*/
public List getErrorTrace() {
// TODO Auto-generated method stub
return null;
}
}