IValuePresence.java

/**
 * <copyright>
 * 
 * Copyright (c) 2010-2016  Thales Global Services S.A.S.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 *    Thales Global Services S.A.S. - initial API and implementation
 * 
 * </copyright>
 */
package org.eclipse.emf.diffmerge.api.diff;

import org.eclipse.emf.ecore.EStructuralFeature;


/**
 * A difference which is due to the unmatched presence of a value on some feature
 * in a given comparison role.
 * @author Olivier Constant
 */
public interface IValuePresence extends IElementRelativeDifference,
IPresenceDifference, IMergeableDifference {
  
  /**
   * Return the feature holding the value (null stands for root containment)
   */
  EStructuralFeature getFeature();
  
  /**
   * Return the difference, if any, which is symmetrical to this one. 
   * @see IValuePresence#isSymmetricalTo(IValuePresence)
   * @return a potentially null value presence (always null if upper bound is not 1 and !isOrder())
   */
  IValuePresence getSymmetrical();
  
  /**
   * Return the non-null value being held
   * @return a non-null object
   */
  Object getValue();
  
  /**
   * Return whether the unmatched presence is solely due to a different ordering.
   * If true, then [getFeature() == null || getFeature().isMany()] and
   * getSymmetrical() returns the opposite ordering difference.
   */
  boolean isOrder();
  
  /**
   * Return whether the given value presence corresponds to this one in the opposite role.
   * True may only be returned if the setting (element and feature) is the same.
   * If the feature is of upper bound 1 or isOrder(), then true is returned when the
   * given value presence describes a different value in the same setting.
   * If the feature is many and !isOrder(), then false is always returned.
   * @param peer_p a non-null value presence
   */
  boolean isSymmetricalTo(IValuePresence peer_p);
  
}