/*______________________________________________________________________________
 * 
 * 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 f�vr. 2005
 *
 */
package rationals.properties;

import java.util.List;
import java.util.Set;

import rationals.Automaton;
import rationals.State;

/**
 * An interface for computing equivalences between automata.
 * 
 * This interface allows definition of various relation between 
 * states.
 * 
 * @author nono
 * @version $Id: Relation.java 2 2006-08-24 14:41:48Z oqube $
 */
public interface Relation {

    /**
     * Sets the context for computing the relation.
     * This method must be called before {@link equivalent(State,State)}.
     * 
     * @param a1
     * @param a2
     */
    void setAutomata(Automaton a1,Automaton a2);
    
    /**
     * Assert the equivalence between two states.
     * This method returns true if and only if the two states
     * are in relation.
     * 
     * @param s1
     * @param s2
     * @return true is s1 ~ s2, false otherwise 
     */
    boolean equivalence(State s1,State s2);


    /**
     * Asset the equivalence between two set of states.
     * This method returns true if and only if the two states set 
     * are equivalent.
     * 
     * @param nsa a Set of State objects from a
     * @param nsb a Set of State objects from b
     * @return true if nsa is equivalent to nsb
     */
    public boolean equivalence(Set nsa, Set nsb);
    
    /**
     * Returns the trace of labels that lead to an error.
     * 
     * @return a List of objects or null.
     */
    public List getErrorTrace();

}