/*______________________________________________________________________________
 * 
 * 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 1 avr. 2005
 *
 */
package rationals;

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

/**
 * An interface for defining various synchronization schemes.
 * This interface is used in {@see rationals.transformations.Synchronize} for
 * and allows various strategies of synchronization between transitions
 * of two automata.
 * 
 * @author nono
 * @version $Id: Synchronization.java 2 2006-08-24 14:41:48Z oqube $
 */
public interface Synchronization {

    /**
     * Synchronize two transitions.
     * This method should return a letter denoting the result of synchronizing 
     * the two transitions' labels. If the result is <code>null</code>, then no synchronization
     * occurs.
     * 
     * @param t1 first label to synchronize
     * @param t2 second label to synchronize
     * @return a non null Object if the two transitions can be synchronized.
     */
    Object synchronize(Object t1, Object t2);
    
    /**
     * Compute the synchronizable letters from two alphabets.
     * This method returns the set of letters from a and b that can be synchronized.
     * In the default case, this method simply computes the intersection of the two
     * sets.
     * 
     * @param a an alphabet 
     * @param b another alphabet
     * @return a new Set of letters (may be empty) from a and b that can be synchronized.
     */
    Set synchronizable(Set a,Set b);

    /**
     * Construct the synchronization alphabet from a collection of
     * alphabets.
     * 
     * @param alphl
     * @return a Set implementation containing all letters of all alphabets 
     * in <code>alphl</code> that could be synchronized.
     */
    Set synchronizable(Collection alphl);

    /**
     * Checks whether or not the given letter is synchronizable in the
     * given automaton's alphabet.
     * This method checks in a synchronization dependant way that the 
     * given letter pertains to the synchronization set.
     *  
     * @param object the letter to check
     * @param alph the alphabet
     * @return true if object is synchronizable with some letter in <code>alph</code>, 
     * false otherwise.
     */
    boolean synchronizeWith(Object object, Set alph);
    
}