public function @ax-lib-flex-animation-code-10-org-as3lib-kitchensync-action-KSSimultaneousEndGroup (... children) {
                          super();
                          for (var i:int = 0; i < children.length; i++) {
                                  if (children[i] is IAction) {
                                          var action:IAction = IAction(children[i]);
                                          addAction(action); 
                                  } else {
                                          throw new TypeError ("All children must be of type IAction. Make sure you are not calling start() on the objects you've added to the group. Found " + getQualifiedClassName(children[i]) + " where IAction was expected.");
                                  }
                          }
                  }
                  
                  override public function update(currentTimestamp:Timestamp):void {
                          if (startTimeHasElapsed) {
                                  var childAction:IAction;
                                  // if the group isn't already running...
                                  if (!childrenAreRunning) {
                                          // reset the number of running children.
                                          _runningChildren = 0;                                
                                          // cache the longest duration
                                          _longestItemsTotalDuration = getLongestItemsTotalDuration();
                                          // reset the dictionary.
                                          _childStartTimes = new Dictionary(true);
                                          
                                          // for all child actions
                                          childAction = null;
                                          for each (childAction in childActions) {
                                                  // add the start time to a dictionary.
                                                  _childStartTimes[childAction] = calculateStartTime(childAction, _longestItemsTotalDuration);
                                                  
                                                  // add a listener to each action so that the completion of the entire group can be tracked.
                                                  childAction.addEventListener(KitchenSyncEvent.START, onChildStart);
                                                  childAction.addEventListener(KitchenSyncEvent.COMPLETE, onChildFinished);
                                                  
                                                  //trace("final start time: " + _childStartTimes[childAction]);
                                          }
                                          // once this has started, it doesn't need updates anymore.
                                          //unregister();
                                  }
                                  
                                  childAction = null;
                                  // Once it's running, for all child actions
                                  for each (childAction in childActions) {
                                          // check to see if start time has elapsed for the child.
                                          if (isChildStartTimeElapsed(childAction, currentTimestamp)) {
                                                  // if so, start the child.
                                                  childAction.start();
                                                  // add one running child.
                                                  _runningChildren++;
                                          }
                                  }
                                  // if all children are running, unregister the group.
                                  if (_runningChildren >= _childActions.length) { unregister(); }
                          }
                  }