An enterprise has various systems including a selling and bookkeeping systems, the production control system among which is generally said to be an ill-structured system. This means that there are many ambiguous parts in the system and the control level of each company is also different, making the system difficult to pattern, compared to well-structured systems with their quite clear structure such as a personnel or bookkeeping system.

From the point of view of system building, the production control system is also one of the most difficult ones among them. This is mainly attributed to the fact that there are so many divisions related to the system and thus the interested ones are difficult to adjust, in addition to the fact that the system is ambiguous. The FIG. 3 shows the relationship between the production control system and other divisions. The order information received from customers is sent to a factory through the sales. In the factory, the operations division usually serves as contacts between them, and prepares a production plan together with the planning division. Based on this plan, a purchasing and processing/assembling plans are formed, where most divisions engaging in the actual production jobs such as material, purchasing, subcontracting, warehouse, processing, assembling, engineering, etc. are involved.

Therefore, the production control system can be said to be opaque, difficult to understand, complicated with each division's different purpose, and hard to build. Here, the emphasis is put on the jobs of each division related to the production control system, making the problems occurring there clear. Then the function of production control system to solve them is shown and the important key terms extracted there are illustrated as a system diagram.