 	import flare.vis.operator.IOperator;
 	import flare.vis.operator.OperatorList;
 	
+	import flash.display.DisplayObject;
 	import flash.display.Sprite;
 	import flash.events.Event;
 	import flash.geom.Rectangle;

		 */
		protected function dataAdded(evt:DataEvent):void
		{
			if (evt.node != null) {
				_marks.addChild(evt.node);
			} else {
				_marks.addChildAt(evt.item, 0);
			}
		}
		

		 */
		protected function dataRemoved(evt:DataEvent):void
		{
			for each (var d:DisplayObject in evt.items)
				_marks.removeChild(d);
		}

	} // end of class Visualization
