In a factory, a lot of items such as products, assemblies, parts, and raw materials are handled. In terms of the demand of these items, there are two types: the items whose demand occurs independently of other items, and the items whose demand is required depending on another demand. The former is Independent Demand item, and the latter is called Dependent Demand item.

Generally, Independent Demand Items, which have no direct relationship with other demands, are requested only according to the forecast. Such items include products, service parts, which are usually handled by the Sales division. The demand of such items occurs for each individual item from customers, and thus each item has no relationship with each other. The Independent Demand Items are used for forecasting and production planning.