Tham khảo tài liệu 'supply chain, the way to flat organisation part 6', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Operational Management of Supply Chains A Hybrid Petri Net Approach 141 According to the Wortmann classification Wortmann 1983 three SC managing policies are followed in practice Make-To-Stock MTS Make-To-Order MTO and Assemble-To-Order ATO or Build-To-Order BTO . In particular in order to deliver on time the produced goods to end-users the MTS strategy governs the system initiating production before the actual occurrence of demands so that end customers are satisfied from stocks of inventory of finished goods. Often under MTS management stocks in the SC are governed by a reorder point based policy and inventory is replenished as soon as a preset reorder level is reached so that the target level is maintained. On the other hand in the MTO technique customer orders trigger the flow of materials and the requirements at each production stage of the SC. Hence under such a management strategy a lower level of material and product inventory is maintained. Furthermore the ATO or BTO policy can be viewed as a hybrid of the former two strategies basically applying MTS in the first stages of the SC and MTO in the last stages Viswanadham Raghavan 2000 . An additional production management choice is made between push and pull strategies Hopp Spearman 2004 a pull production policy explicitly limits the amount of work-in-process that can be in the system while in a push one no explicit limit on the amount of work-in-process is defined. Wellknown push systems are the Material Requirements Planning MRP approach and the Manufacturing Resources Planning technique also known as MRP II Hopp Spearman 2004 . Well-established pull strategies are the just-in-time technique based on Kanbans and the CONWIP or CONstant Work-In-Process strategy Hopp Spearman 2004 Spearman et al. 1990 which is a generalized form of the Kanban policy while the latter procedure establishes a fixed limit on work-in-process in a part of the system via the limited number of Kanban cards the CONWIP strategy limits .