/*
 * 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;

/**
 * A derivation event listener a couple of "hooks" to customize the derivation
 * process. These methods are called before the derivation, and whenever results are 
 * added to the final result set.
 * <br>
 * Implementations should be stateless (i.e. there should be no instance variables
 * and should have a public parameterless constructor. I.e., an instance can be build
 * from the class name.
 * @author <A HREF="mailto:mandarax@jbdietrich.com">Jens Dietrich</A>
 * @version 3.3.1 <9 August 2004>
 * @since 3.2
 */

public interface DerivationEventListener {
	/**
	 * This method is executed before a result set is added to the result set.
	 * @param session a session object
	 */
	public void onResultDo(Session session) throws InferenceException ;
	/**
	 * This method is executed before the IE starts the derivation.
	 * @param session a session object
	 */
	public void beforeDerivationDo(Session session) throws InferenceException ;

}
