/*
 * Copyright (C) 1999-2004 <a href="mailto:mandarax@jbdietrich.com">Jens Dietrich</a>
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2 of the License, or (at your option) any later version.
 *
 * This library 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
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */
package org.mandarax.kernel;


/**
 * Interface for strategies defining the order of literals that is used by
 * the inference engine when it attempts to unify the literals with a clause.
 * @author <A HREF="mailto:mandarax@jbdietrich.com">Jens Dietrich</A>
 * @version 3.3.1 <9 August 2004>
 * @since 1.1
 */
public interface SelectionPolicy {

    /**
     * Return an array of integers specifying in which order the inference engine
     * should attempt to unify the literals with the candidate.
     * The order of clauses matters, this order may have an important impact on performance of a proof!
     * E.g., if {A,B,C} is a goal (all symbols represent negative literals),
     * then a left most selection rule would mean that we first try to unify A with
     * appliedClaue, then B and finally C. The array returned should then be {0,1,2}.
     * @return int[] the positions
     * @param goal the goal
     * @param appliedClause the clause that should be used to prove the goal
     */
    int[] getOrderedPositions(Clause goal, Clause appliedClause);
}
