/*
 * 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 representing queries. Queries consist of one or many facts and a common name.
 * The inference engine then tries to replace the variables in these facts by constants, using
 * the knowledge in a knowledge base.
 * <br>
 * DerivationEventListeners can be attached to a query. If the IE supports them (use the feature descriptor 
 * of the IE to find out) the respective callback will be called by the IE.
 * @see org.mandarax.kernel.Fact
 * @see org.mandarax.kernel.LogicFactory
 * @see org.mandarax.kernel.DerivationEventListener
 * @author <A HREF="mailto:mandarax@jbdietrich.com">Jens Dietrich</A>
 * @version 3.3.1 <9 August 2004>
 * @since 1.9
 */
public interface Query extends PropertiesSupport {

    /**
     * Get the facts.
     * @see org.mandarax.kernel.Fact
     * @return an array of facts
     */
    public Fact[] getFacts();
    /**
     * Set the facts.
     * @see org.mandarax.kernel.Fact
     * @param facts an array of facts
     */
    public void setFacts(Fact[] facts);
    /**
     * Get the common name of this query, i.e., something like "Find the oncle of a person".
     * @return a string
     */
    public String getName();

    /**
     * Set the common name of this query.
     * @param a name
     */
    public void setName(String queryName);
    /**
     * Get the registered derivation event listener.
     * @return the derivation event listeners
     */
    public DerivationEventListener[] getDerivationEventListeners() ;
    /**
     * Set the derivation event listeners.
     * @param listeners listeners
     */
    public void setDerivationEventListeners(DerivationEventListener[] listeners) ;
}
