loadandquerykb.java

Mandarax是一个规则引擎的纯Java实现。它支持多类型的事实和基于反映的规则

/*
 * Copyright (C) 1999-2004 <A href="http://www-ist.massey.ac.nz/JBDietrich" target="_top">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.examples.db;

import java.io.File;
import org.mandarax.kernel.*;
import org.mandarax.reference.ResolutionInferenceEngine;
import org.mandarax.util.LogicFactorySupport;
import org.mandarax.zkb.*;

/**
 * A class that shows the integration of knowledge base in application programs. 
 * The knowledge base is loaded from the file generated by CreateKB and then queried. 
 * The results of the queries are printed to the console. 
 * <p>
 * Mandarax uses other (open source) libraries such as JDOM, the apache log4j
 * logging library and the junit testing framework. The mandarax distribution 
 * contains the respective libraries. Please but these jar files in the classpath 
 * before running the example! In addition, the JDBC driver for the database used must 
 * also be in the classpath.
 * @since 2.2
 * @author <A href="http://www-ist.massey.ac.nz/JBDietrich" target="_top">Jens Dietrich</A>
 * @version 3.4 <7 March 05>
 */
public class LoadAndQueryKB {
	private KnowledgeBase kb = null;
	private LogicFactorySupport lfs = new LogicFactorySupport();
	private InferenceEngine ie = new ResolutionInferenceEngine();

	/**
	 * Load the knowledge base and query it.
	 */
	public static void main(String[] args) {
		// uncomment the following line to switch on logging
		// org.apache.log4j.BasicConfigurator.configure();
		
		LoadAndQueryKB inst = new LoadAndQueryKB();
		inst.loadKB();
		inst.calculateDiscount("Tom");
		inst.calculateDiscount("John");
		inst.calculateDiscount("Jim");
		inst.calculateDiscount("Ralf");
		inst.calculateDiscount("Bill");		
	}
	/**
	 * Load a knowledge base from the XML file.
	 */
	public void loadKB() {
		ZKBManager zkbManager = new ZKBManager();
		try {
			kb = zkbManager.importKnowledgeBase(new File("kb.zip"));
			System.out.println("Knowledge base loaded from kb.zip");
		}
		catch (ZKBException x) {
			System.err.println("Cannot import knowledge base from kb.zip - use CreateKB to generate knowledge base !");
			x.printStackTrace();
		}	
	}	
	/**
	 * Query a knowledge base for the discount of a particular customer.
	 * @param customer a customer (name)
	 * @return a discount
	 */
	public void calculateDiscount(String customerName) {
		// build query
		Class[] struct = { String.class, Discount.class };
		VariableTerm queryVariable = (VariableTerm)lfs.variable("discount", Discount.class);
		Predicate p = new SimplePredicate("a customer gets a discount", struct);
		Query query = lfs.query(lfs.fact(p,customerName,queryVariable),"get discount for "+customerName);
		
		// issue query
		try {
			ResultSet rs = ie.query(query,kb,InferenceEngine.ONE,InferenceEngine.BUBBLE_EXCEPTIONS);
			Discount discount = null;
			while (rs.next()) {
				discount = (Discount)rs.getResult(queryVariable);
				System.out.println("The discount for " + customerName + " is " + discount);				
			}
		}
		catch (InferenceException x) {
			System.out.println("Cannot compute discount for " + customerName);
			x.printStackTrace();
		}
	}	
}