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.
   */
  
  /*
   *    StructureProducer.java
   *    Copyright (C) 2011 University of Waikato, Hamilton, New Zealand
   *
   */
  
  package weka.gui.beans;
  
  import weka.core.Instances;
  
  /**
   * Interface for something that can describe the structure of what
   * is encapsulated in a named event type as an empty set of
   * Instances (i.e. attribute information only). For example,
   * batchAssociationRulesEvent can be described as LHS (String), RHS (String)
   * and a number of metrics (Numeric); dataSetEvent, instanceEvent, 
   * trainingSetEvent etc. are all straightforward, since they already
   * encapsulate instances; textEvent can be described in terms of
   * the title (String) and the body (String) of the text. Sometimes
   * it is not possible to know the structure of the encapsulated output
   * in advance (e.g. certain filters may not know how many attributes
   * will be produced until the input data arrives), in this case
   * any implementing class can return null to indicate this. 
   * 
   * @author Mark Hall (mhall{[at]}pentaho{[dot]}com)
   * @version $Revision: 7422 $
   *
   */
  public interface StructureProducer {
    
    /**
     * Get the structure of the output encapsulated in the named
     * event. If the structure can't be determined in advance of
     * seeing input, or this StructureProducer does not generate
     * the named event, null should be returned.
     * 
     * @param eventName the name of the output event that encapsulates
     * the requested output.
     * 
     * @return the structure of the output encapsulated in the named
     * event or null if it can't be determined in advance of seeing input
     * or the named event is not generated by this StructureProduce.
     */
    public Instances getStructure(String eventName);
  }
  