is the process of specifying production and inventory levels in order to meet projected demand. It is a fundamental step for all goods-producing companies, and has been performed in one form or other since the advent of mass production. The (ROP) approach, still in vogue today, has been practiced since the industrial revolution. The (TPS), introduced in the 1950s, was a revolutionary approach that helped rethink the flow of materials in a factory. The next development of note was (MRP), developed in 1964 by Joseph Orlicky. MRP is a rigorous demand-driven approach to coordinating material requirements across finished goods, sub-assemblies, and raw materials. The advent of (APS) in the 1990s helped address some of the drawbacks of MRP, especially related to multisite production facilities and capacity constraints.