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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 
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    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
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*/
//#########################################################################
//	Consultable
//#########################################################################

package ubc.cs.JLog.Terms;

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

/**
* iConsultable is the interface for classes that may need to
* access the knowledge base before any proof attempts are made.
* Usually such consulting is done after the knowledge base changes, such as
* when a prolog source is consulted.  The usual purpose of such consulting is to 
* prefetch and cache the knowledge base entries so that a search of the 
* knowledge base during the proof phase is not required.
*
* @author       Glendon Holst
* @version      %I%, %G%
*/
public interface iConsultable
{
 /**
  * Consult the given jKnowledgeBase and cache any invariant values (those 
  * which would not change until the next time the jKnowledgeBase changes). 
  * Where possible, consultable objects should minimize computation and assume that any 
  * cached values are still accurate.
  *
  * @param kb 		the knowledge base which attempted proofs are based upon.
  */
 public void 		consult(jKnowledgeBase kb);
 
 /**
  * Called when the jKnowledgeBase changes. Should set all cached values to 
  * dirty so that a  following call to consult would perform a full lookup 
  * as required.
  *
  */
 public void 		consultReset();
 
 /**
  * Determine if cached values already exist and hence if consulting is required. If 
  * object does not knowimmediatly whether consulting is needed, then assuming it is 
  * required.
  *
  * @return 		false if cached values are valid, 
  * 			true otherwise, if consult should be
  * 			called.
  */
 public boolean 	isConsultNeeded();
};