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/*
 * @(#)SIChangeEvent.java	1.25 00/08/28
 *
 * Copyright 1998-2000 by Sun Microsystems, Inc.,
 * 901 San Antonio Road, Palo Alto, California, 94303, U.S.A.
 * All rights reserved.
 * 
 * This software is the confidential and proprietary information
 * of Sun Microsystems, Inc. ("Confidential Information").  You
 * shall not disclose such Confidential Information and shall use
 * it only in accordance with the terms of the license agreement
 * you entered into with Sun.
 */

package javax.tv.service;

import java.util.EventObject;


/**
 * SIChangeEvent objects are sent to
 * SIChangeListener instances to signal detected changes
 * in the SI database.
 *
 * Note that while the SI database may detect changes, notification of
 * which specific SIElement has changed is not guaranteed.
 * The entity reported by the method getSIElement() will
 * be either:
 * 

 * The specific SI element that changed, or
 * 
An SI element that contains, however indirectly, the specific SI
 * element that changed, or
 * 
null, if the specific changed element is unknown.
 * 
 * 
 * The level of specificity provided by the change mechanism is
 * entirely dependent on the capabilities and current resources of the
 * implementation.
 *
 * SIChangeEvent instances also report the kind of change
 * that occurred to the SI element, via the method
 * getChangeType():
 * 
 *
 * An SIChangeType of ADD indicates that
 * the reported SI element is new in the database.
 *
 * 
An SIChangeType of REMOVE indicates
 * that the reported SI element is defunct and no longer cached by the
 * database.  The results of subsequent method invocations on the
 * removed SIElement are undefined.
 *
 * 
An SIChangeType of MODIFY indicates
 * that the data encapsulated by the reported SI element has changed.
 * 
 * 
 *
 * In the event that the SIElement reported by this event is not
 * the actual element that changed in the broadcast (i.e. it is
 * instead a containing element or null), the
 * SIChangeType will be MODIFY.
 * Individual SI element changes are reported only once, i.e.,
 * a change to an SI element is not also reported as a change
 * to any containing (or "parent") SI elements.
 *
 * @see #getSIElement
 * @see #getChangeType
 */
public abstract class SIChangeEvent extends EventObject {

  
  /**
   * Constructs an SIChangeEvent object.
   *
   * @param source The entity in which the change occurred.
   *
   * @param type The type of change that occurred.
   *
   * @param e The SIElement that changed, or
   * null if this is unknown.
   */
  public SIChangeEvent(Object source, SIChangeType type, SIElement e) {
    	super(null);
  }
  
  /**
   * Reports the SIElement that changed.
   * 
   * This method may return null, since it is not
   * guaranteed that the SI database can or will determine which
   * element in a particular table changed.
   *
   * @return The SIElement that changed, or
   * null if this is unknown.  */
  public SIElement getSIElement() {
	return null;
  }
  
  /**
   * Indicates the type of change that occurred.
   *
   * @return The type of change that occurred.
   */
  public SIChangeType getChangeType() {
	return null;
  }
}