This paper reports a case study in applying Constraint-Satisfaction techniques to university and school timetabling. It involves the construction of a substantial, carefully specified, fully tested and fully operational system. The software engineering aspect of Constraint-Satisfaction is emphasized in this paper. Constraint-Satisfaction problems are expressed in a language more familiar to the formal software engineering community. This brings Constraint-Satisfaction one step closer to formal specification, program verification and transformation; issues extensively studied in software engineering. In problem formulation, explicit domain constraints and heuristic information are made explicit. Moreover, the user's needs are considered more closely; for instance, when the program fails to find a solution, useful indications are produced to help in relaxation or reformulation of the problem.
