Design pattern literature commonly refers to views as «dumb» given that their knowledge of models and controllers in an application is limited. This differs from the Observer pattern as it allows any subscriber implementing an appropriate event handler to register for and receive topic notifications broadcast by the publisher. Events Both the event aggregator and mediator use events, in the above examples. An event aggregator obviously deals with events – it’s in the name after all. They’re often an indication that modules in a system are either tightly coupled or that logic is overly spread across multiple parts of a codebase.