XP_NewObserverList
XP_DisposeObserverList
XP_GetObserverListObservable
XP_SetObserverListObservable
XP_AddObserver
XP_RemoveObserver
XP_NotifyObservers
XP_DisableObserverNotification
XP_EnableObserverNotification
XP_IsObserverNotificationEnabled