     public function ViewNavigator()
     {
         super();
+        
+        if (!classAliasesRegistered)
+        {
+            // Register aliases for custom classes that will be written to
+            // persistence store by navigator
+            registerClassAlias("ViewDescriptor", ViewDescriptor);
+            registerClassAlias("NavigationStack", NavigationStack);
+            
+            classAliasesRegistered = true;
+        }
         
         // Default view transitions
         var slideLeft:SlideViewTransition = new SlideViewTransition();

     */     
    private static const DEFAULT_VIEW_TRANSITION_DURATION:Number = 300;
    
    //--------------------------------------------------------------------------
    //
    //  Constructor

package spark.components
{
import flash.events.Event;
import flash.net.registerClassAlias;

import mx.core.IVisualElement;
import mx.core.UIComponent;
