An MRP or other planning system generation that only recalculates requirements for items that have changed since the last generation, due to the addition or changes in order quantities and dates, inventory levels, bill of material or routings, lead times or other parameters. A flag is usually set by programmes that initiate changes for those items, which is used by MRP as the basis to regenerate them. It typically reduces generation time and is most useful for companies that have many part numbers, a small percentage of which are active in a given week.