4ca1e4ba_Pattern_for_Event_Notification_son_with_Mediator_and_Observer_Event_Notifier
[0] Relationship between publishers and subscribers [Mediator] Many-to-many [Observer] One-to-many, as an observer may only observe a single subject [Event Notifier] 
Many-to-many
Event Notifier, a Pattern for Event Notification
Event Notifier