Without a manufacturing schedule, workpiece materials don’t arrive on time, machine tools sit idle and customers fume. However, scheduling is difficult, especially when multiple-level assemblies and large numbers of components are involved. To meet this need, software companies have developed complex, integrated enterprise resource planning (ERP) systems. Hundreds of such systems exist, from giant multisite suites able to manage (OEMs’) needs to those suitable for a job shop with a handful of employees.