In this paper we introduce some aspects of the development process of a production planning tool for a leading European car manufacturer. In this project we had to face a gap between theoretical problem definition in manufacturing planning and control and the actual requirements of the dispatcher. Especially the determination of production capacities and product processing times was a severe problem. The software system had to support the derivation of these important variables from shift plans, factory calendars and exceptional events. In order to implement this we defined a formal model that is a combination of the theoretical and practical view on manufacturing problem. The Model for Serial Manufacturing allows the dispatcher to provide up-to-date information in an easier way then provided by standard ERP systems about the production systems and transfers the information automatically to planning algorithms. Thus the production planning and control is always performed on the most recent information.