content: /*
   *    This program 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.
   *
   *    This program 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 this program; if not, write to the Free Software
   *    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
   */
  
  /*
   *    ResultListener.java
   *    Copyright (C) 1999 University of Waikato, Hamilton, New Zealand
   *
   */
  
  
  package weka.experiment;
  import java.io.Serializable;
  
  /**
   * Interface for objects able to listen for results obtained
   * by a ResultProducer
   *
   * @author Len Trigg (trigg@cs.waikato.ac.nz)
   * @version $Revision: 1.7 $
   */
  
  public interface ResultListener extends Serializable {
  
    /**
     * Determines if there are any constraints (imposed by the
     * destination) on additional result columns to be produced by
     * resultProducers. Null should be returned if there are NO
     * constraints, otherwise a list of column names should be
     * returned as an array of Strings.
     * @param rp the ResultProducer to which the constraints will apply
     * @return an array of column names to which resutltProducer's
     * additional results will be restricted.
     * @exception Exception if an error occurs
     */
    String [] determineColumnConstraints(ResultProducer rp) 
      throws Exception;
  
    /**
     * Prepare for the results to be received.
     *
     * @param rp the ResultProducer that will generate the results
     * @exception Exception if an error occurs during preprocessing.
     */
    void preProcess(ResultProducer rp) throws Exception;
    
    /**
     * Perform any postprocessing. When this method is called, it indicates
     * that no more results will be sent that need to be grouped together
     * in any way.
     *
     * @param rp the ResultProducer that generated the results
     * @exception Exception if an error occurs
     */
    void postProcess(ResultProducer rp) throws Exception;
    
    /**
     * Accepts results from a ResultProducer.
     *
     * @param rp the ResultProducer that generated the results
     * @param key an array of Objects (Strings or Doubles) that uniquely
     * identify a result for a given ResultProducer with given compatibilityState
     * @param result the results stored in an array. The objects stored in
     * the array may be Strings, Doubles, or null (for the missing value).
     * @exception Exception if the result could not be accepted.
     */
    void acceptResult(ResultProducer rp, Object [] key, Object [] result)
      throws Exception;
  
    /**
     * Determines whether the results for a specified key must be
     * generated.
     *
     * @param rp the ResultProducer wanting to generate the results
     * @param key an array of Objects (Strings or Doubles) that uniquely
     * identify a result for a given ResultProducer with given compatibilityState
     * @return true if the result should be generated
     * @exception Exception if it could not be determined if the result 
     * is needed.
     */
    boolean isResultRequired(ResultProducer rp, Object [] key) 
      throws Exception;
  
  }
  