Progress in integrating and optimizing production plans and schedules

Over the past twenty years two widely accepted approaches to integrated production planning and scheduling systems have emerged. The first approach was based on materials requirements planning (MRP). This approach emphasizes minimizing inventory while meeting order due dates. The second approach was heirarchical production planning (HPP). This approach emphasizes cost minimization and efficient utilization of capacity. This paper reviews the evolutionary development of each of these integrated systems and concludes by discussing the environment where each is best suited.