The manufacturing of a factory is a demand-driven process. The driving source of the OEM business is the sales order. The sales order is calculated by MRP and can be broken down into a series of production orders. There are many relationships between production orders and sales orders, and between production orders and production orders (i.e., 1:n, n:n relationships). Of course, there is also a correspondence between the production order and the purchase order. For example, in the business process of the following manufacturing enterprises, a sales order (single line) has 6 production orders according to BOM decomposition, and there is a series and parallel relationship between the production orders
Forging machining assembly is a series relationship, stamping injection molding is a series relationship, stamping spraying is a series relationship and is a parallel relationship. 
In a production order, there are generally multiple processes. There is a tandem relationship between operations and operations.
In daily production scenarios, we often need to query the progress relationship of subordinate production orders based on sales orders or sales order lines. To determine which part of the production process (production order) is progressing is delayed. Therefore, it is necessary to establish a multi-level correlation relationship between sales order, production order, and production order to achieve dynamic tracking (combined with MES reporting) and query the progress of the process level.
In order to establish the association between sales orders (sales order lines) and multi-level production orders, it is generally necessary to carry out detailed scheduling of the whole factory and multiple workshops, and at least to realize the detailed scheduling of the whole factory, multiple workshops and key processes, so as to establish a balance between the materials and production capacity of the whole factory. This establishes the relationship between the sales order (sales order line) and the multi-level production order.