A system built around MRP that also includes production planning, master production schedule, and capacity requirements planning. Once the planning phase is complete and the plans have been accepted as realistic and attainable, the execution functions come into play. These include the shop floor control functions of input/output measurement, detailed scheduling and dispatching, as well as anticipated delay reports from both the shop and vendors, purchasing follow-up and control, and other functions. The term “closed loop” implies that not only is each of these elements included in the overall system, but also that there is feedback from the execution functions so the planning can be kept valid at all times.