Supply chain management rose to prominence as a major management issue in the last decade. While the focus of managing supply chains has undergone a drastic change as a result of improved information technology, production planning remains a critical issue. We begin with optimization models that map to mrp and MRP II and end up as a basis for a planning model. In order to produce a useful model, we add extensions and ultimately arrive at models that bear little resemblance to mrp and certainly solutions for the optimization problems cannot be obtained using mrp or MRP II processing or logic. Connections with hierarchical systems for planning and detailed scheduling are outlined.