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/*
    This file is part of JLog.

    Created by Glendon Holst for Alan Mackworth and the 
    "Computational Intelligence: A Logical Approach" text.
    
    Copyright 1998, 2000, 2002 by University of British Columbia and 
    Alan Mackworth.
    
    This notice must remain in all files which belong to, or are derived 
    from JLog.
    
    Check  or 
     for further information
    about JLog, or to contact the authors.
     
    JLog is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation; either version 2 of the License, or
    (at your option) any later version.

    JLog 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 General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with JLog; if not, write to the Free Software
    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
    URLs:  or 
*/
//#########################################################################
//	Knowlege Base
//#########################################################################

package ubc.cs.JLog.Foundation;

import java.lang.*;
import java.util.*;
import ubc.cs.JLog.Terms.*;

/**
 * The Prolog rule definitions database. 
 *
 * @author       Glendon Holst
 * @version      %I%, %G%
 */
public class jKnowledgeBase
{
 protected Hashtable 					definitions;
 
 public jKnowledgeBase()
 {
  definitions = new Hashtable();
 };

 /**
  * Use this method to set all the rules for a particular predicate definition at once.
  * Unlike the separate addRule methods, this method only updates the rule
  * definition if it does not already exist.  It is an error if the definition already exists
  * and belongs to a different library.
  *
  * @param rds		The rule definition to add.
  */
 public void			addRuleDefinitions(jRuleDefinitions rds)
 {jRuleDefinitions		rdsmatch;
  
  if ((rdsmatch = getRuleDefinitionsMatch(rds)) == null)
   definitions.put(getKeyString(rds),rds);
  else if (!rdsmatch.sameLibrary(rds.getLibrary()))
  {String		err;
	 
   err = "Rules " + rdsmatch.getName() + "/" + rdsmatch.getArity() + 
			" already exists" + 
			(rdsmatch.getLibrary() != null ? " in library " + rdsmatch.getLibrary() : "");
  
   throw new UnmatchedRuleException(err);
  }
 };

 public void 			addRule(jRule r)
 {jRuleDefinitions 	rds;
  
  if ((rds = getRuleDefinitionsMatch(r)) == null)
   definitions.put(getKeyString(r),rds = new jRuleDefinitions(r.getName(),r.getArity()));
 
  rds.addRule(r);
 };
 
 public void 			addRuleFirst(jRule r)
 {jRuleDefinitions 	rds;
  
  if ((rds = getRuleDefinitionsMatch(r)) == null)
   definitions.put(getKeyString(r),rds = new jRuleDefinitions(r.getName(),r.getArity()));
 
  rds.addRuleFirst(r);
 };
 
 public void 			addRuleLast(jRule r)
 {jRuleDefinitions 	rds;
  
  if ((rds = getRuleDefinitionsMatch(r)) == null)
   definitions.put(getKeyString(r),rds = new jRuleDefinitions(r.getName(),r.getArity()));
 
  rds.addRuleLast(r);
 };
 
 public void 			removeRule(jRule r)
 {jRuleDefinitions 	rds;

  if ((rds = getRuleDefinitionsMatch(r)) != null)
   rds.removeRule(r);
 };
 
 public void 			clearRules()
 {
  definitions = new Hashtable();
 };
 
 public Enumeration 	enumDefinitions()
 {
  return definitions.elements();
 };

 /**
  * Convert a set of rules matching the given name and arity to dynamic rules.
  *
  * @param r  		The name and arity of the rule set to convert.
  */
 public synchronized void 	makeRuleDefinitionDynamic(iNameArity r)
 {jRuleDefinitions 		rds;
 
  rds = getRuleDefinitionsMatch(r);
  
  if (rds == null)
   definitions.put(getKeyString(r),new jDynamicRuleDefinitions(r.getName(),r.getArity()));
  else if (!(rds instanceof jDynamicRuleDefinitions))
   definitions.put(getKeyString(r),new jDynamicRuleDefinitions(rds));
 };
 
 /**
  * Access the set of rules matching the given name and arity.
  *
  * @param r  		The name and arity of the rule set to retrieve.
  *
  * @return  		The jRuleDefinitions rule set, or null if it
  *					doesn't exist.
  */
 public jRuleDefinitions 	getRuleDefinitionsMatch(iNameArity r)
 {
  return (jRuleDefinitions) definitions.get(getKeyString(r));
 };
 
 public void 			consult()
 {Enumeration 		e;
  jRuleDefinitions 	rds;

  e = enumDefinitions();
  while (e.hasMoreElements())
  {
   rds = (jRuleDefinitions) e.nextElement();
   rds.consult(this); 
  }
 };
 
 protected String		getKeyString(iNameArity r)
 {
  return r.getName() + "/" + Integer.toString(r.getArity());
 }; 
};