The event notification pattern works by emitting events to subscribers once a command is executed. This can be compared to the observer pattern in which you observe a subject that has a list of many listeners or subscribers that are automatically notified when the state of the observed object changes.
This behavior is widely used by event bus libraries that allow publish-subscribe communication among the components that are part of an application. The most common use cases for these libraries are targeted towards the UI, but they are also applicable to other parts of the system in the backend. The following diagram demonstrates how an event is sent to the bus and then propagated to all subscribers, which were previously ...
