Mediator promotes loose coupling by keeping objects from referencing to each other explicitly, and lets you vary their interaction independently. Look for Mediator patterns where objects are decoupled and in situations when inter-object behavior variation is present or expected. Mediators well serve situations where complex protocols must be managed, and when centralized access points are desirable.
Mediator is a behavioral pattern.
When we speak of Mediator, it's a system of at least three objects messaging in a star topology. As the number of colleagues increases, the number of total communication pathways is vastly reduced. The horizontal splitter control in Tazmanian Traders, which comes from the tsGen class library in the VFP samples, contains two shapes and two scrolling command buttons. As the handle shape is moved, or the scroll buttons are clicked, messages are sent to the splitter, which then messages selected items on the form. Note that several bridge patterns are evident here separating programming interfaces from implementations.