4ca1e4ba_Pattern_for_Event_Notification_son_with_Mediator_and_Observer_Event_Notifier
[0] Knowledge of who can publish and whom to notify of events [Mediator] Localized in the mediator [Observer] Duplicated by each observer and subject [Event Notifier] 
Localized in the event service
Event Notifier, a Pattern for Event Notification
Event Notifier