Representation and processing of preferential rules

Preferential rules occur very often in application domains like timetabling. Besides absolutely valid rules like "Ground courses have to start in the morning in one of the main lecture rooms", there are very often preferential rules like "A wish for the starting time of a lecture should be satisfied with less deviations" or “A wish for a room of a lecture should be satisfied if possible”. Our aim is to develop easy-to-use techniques for applying preferential rules and to demonstrate their use and efficiency. We are motivated by the non-availability of suitable implementations and the need of efficient execution.