The executive layer of MRPII includes workshop operation and purchasing operation, and MES focuses on the execution of workshop operation plan, which enriches the functions of software in workshop control and workshop scheduling to meet the needs of changeable workshop environment. At the same time, in order to adapt to the changing external environment in the process of planning implementation, MRP planning functions should be more flexible, such as strengthening the integration of material planning and capacity planning, automatically replacing materials and routing, adding, subtracting, translating and dividing processes. A perfect MRPII system should include the planned execution function itself. The essence of the problem is the strength of the software's planning execution program function, the interface and integration with the field control facilities, and whether the planning and scheduling function has enough adaptability and flexibility. Some software companies with characteristics in workshop or site management, their partners and users set up Mesa Association in 1992 to develop their business. The organization has grown from the initial 23 companies to more than 200 member units. Manufacturing Execution System (MES) is an information flow used to track production progress, inventory situation, work progress and other operations and management related to entering and leaving the workshop.