In this way, between two revisions the production manager knows for any week which flavors of which type of yoghurt should be produced in which day, in what sequence and in what quantities. Refinements of such a schedule concern only changes to the quantities, within certain limits. Under these conditions, the task of the production manager is two fold. First, at the end of the current week he makes the appropriate refinements or modifications to the schedule for the forthcoming week, based on the stock requirements provided by the inventory control department, and the real condition of the factory. Once required changes have been made and the schedule is fixed (frozen), it is ready for execution.