Imposing policy can be done from above, using FACADE, if that policy needs to be big and visible. On the other hand, if subtlety and discretion are needed, MEDIATOR may be the more appropriate choice. FACADEs are usually the focal point of a convention. Everyone agrees to use the FACADE instead of the objects beneath it. MEDIATOR, on the other hand, is hidden from the users. Its policy is a fait accompli rather than a matter of convention. |