The user interface
nThe user interface is a mechanism for viewing and controlling the solution process. nIt generally is preferable for the model to be as independent of the user interface as possible. nThe interface is usually one of the least stable parts of the system, and often among the last to be finalized in system design. nWe will design our user interface as a client of the model.  The user interface queries the model for information and commands as directed by the user.