Software to implement finite capacity scheduling uses actual production capacity as a key parameter for its scheduling calculation. This is different from the original production scheduling method, MRPII. MRPII assumes infinite capacity, and creates schedules by working back from customer due date. This allows an MRPII schedule to be unachievable, because it assumes no limit on the number of items a workcentre can process in a day. There are many different approaches to finite capacity scheduling, including, for example, constraint based scheduling, and also MRPII add-ons which adjust an MRPII schedule to match actual capacity.