The deterministic demand model may have two types of demand: independent and dependent. It is crucial in an inventory control system to understand the difference between those two demand types as the starting point for an inventory policy. Independent demand is the demand for finished products such as cars or books, and may involve some level of uncertainty as well; while dependent demand focuses on component parts or sub$-$assemblies such as box console sub$-$assemblies for Toyota cars, and is usually considered certain once the end item on which it depends is known. Figure $5$ illustrates the nature of both kinds of demand

In an independent demand environment, the demand for an item does not depend on the demand of another item $($see Figure $5).$ For example, finished goods items do not depend on other items because the focus is on item sale, order processing, or sales forecast. The independent demand for inventory is founded on confirmed forecasts, customer orders, estimation, and past history.

However, unlike independent demand, dependent demand for an item depends on the demand for another item. For instance, raw material and component stocks are dependent on the demand for finished goods. Raw materials and other manufacturing components, for instance, are converted to finished goods through systems such as material resources planning $($MRP$),$ distribution resources planning $($DRP$),$ or enterprise resource planning $($ERP$).$