Preferential rules occur very often in application domains like timetabling. Besides absolutelyvalid rules like"Ground courseshavetostart in the morningi no ne of the main lecture rooms", there are very often preferential rules like" Aw ish fort he starting timeo falecture should be satisfied with less deviations" or "A wish foraroom of alecture should be satisfied if possible". Our aim is to develop easy-to-use techniques fora pplying preferential rules and to demonstrate their use and

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... cy. We are motivated by the non-availabilityo f suitable implementations and the need of efficient execution.