package org.mandarax.reference;


/*
 * 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
 */
 
import java.io.Serializable;
import org.mandarax.kernel.*;
import org.mandarax.util.logging.LogCategories;
/**
 * Algorithm used by the inference engines to evaluate 'semantic' clauses 
 * and terms.
 * @author <A HREF="mailto:mandarax@jbdietrich.com">Jens Dietrich</A>
 * @version 3.3.1 <9 August 2004>
 * @since 2.0
 */
public interface SemanticEvaluationPolicy extends LogCategories, Serializable {

	/**
	 * Try to execute literals in the clause, and remove those literals if the
	 * result ist true. E.g., the result of performing +[]-[L1,L2,2&lt4,L3]
	 * would be +[]-[L1,L2,2&lt4,L3].
	 * This method is used in the actual proof.
	 * @param c a clause
	 * @param session a session object
	 * @param logOn indicates whether we should log
	 * @return another clause
	 */
	Clause evaluate(Clause c,Session session,boolean logOn) ;
	/**
	 * Try to execute a complex term.
	 * This method is used when applying unification in renamings
	 * in the process of result set building.
	 * @param ct a complex term
	 * @param cs the clause set (context object)
	 * @param session a session object
	 * @param logOn indicates whether we should log
	 * @return the term
	 */
	Term evaluate(ComplexTerm c,ClauseSet cs, Session session,boolean logOn) ;
	/**
	 * Try to unify two terms by evaluating them and comparing the results. 
	 * @param t1 the first term
	 * @param t2 the second term
	 * @param session a session object
	 * @return a boolean - true if the terms represent the same object
	 * @param logOn indicates whether we should log
	 */
	boolean evaluateAndCompare(Term t1,Term t2,Session session,boolean logOn) ;
}
