/*
 * 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;


/**
 * Rules are prerequisite / conclusion associations. Note that this class represents
 * only simple rules having only one fact in the head. Prerequisites can be connected
 * by AND or OR.<br>
 * For generalized rules with a disjunction of facts in the head use <code>Clause</code> or <code>ClauseSet</code>.
 * Note that instances are usually created using a factory.
 * @see org.mandarax.kernel.LogicFactory
 * @author <A HREF="mailto:mandarax@jbdietrich.com">Jens Dietrich</A>
 * @version 3.3.1 <9 August 2004>
 * @since 1.0
 */
public interface Rule extends Clause {

    /**
     * Apply a set of replacements to a rule. Returns a new rule!
     * @return the rule that is the result of applying the replacements
     * @param r a collection of replacements
     */
    public Rule applyToRule(java.util.Collection r);

    /**
     * Apply a single replacement to a rule. Return a new rule!
     * @return the rule that is the result of applying the replacement
     * @param r a replacement
     */
    public Rule applyToRule(Replacement r);

    /**
     * Get the body of the rule.
     * @return the body (a list of facts)
     */
    public java.util.List getBody();

    /**
     * Get the head fact.
     * @return the head (conclusion) of the rule
     */
    public Fact getHead();

    /**
     * Indicates whether the premisses in the body are connected by OR.
     * @return a boolean
     */
    boolean isBodyOrConnected();

    /**
     * Set the body.
     * @param b the new body
     */
    public void setBody(java.util.List b);

    /**
     * Set a new value. A value true means that the prerequisistes are connected by OR,
     * a value false means that the prerequistes are connected by AND.
     * @param value a boolean
     */
    public void setBodyOrConnected(boolean value);

    /**
     * Set the head.
     * @param f the new head
     */
    public void setHead(Fact f);
}
