MRP is concerned with both production scheduling and inventory control. It is a material control system that attempts to keep adequate inventory levels to assure that required materials are available when needed. MRP is applicable in situations of multiple items with complex bills of materials. MRP is not useful for job shops or for continuous processes that are tightly linked. MRP was pioneered in the 1970’s with the work of Orlicky. Later evolved or became part of integrated to Manufacturing Resource Planning systems (or MRPII).