Timetable management in universities is a complicated issue which uses up a great deal of human resources and is therefore very costly. This article deals with the analysis and design of an interactive decision support system for timetable management. This tool will be able to take hierarchical data organization into account and maintain coherence of the constraints on this data. Our research which has led to the creation of the tool has three aims. The first aim is to provide an open, generic tool which can be developed in many different ways. In order to achieve these aims, we have followed an object-oriented approach and we have defined object classes dedicated for the modelling of the timetabling problem. The second aim is to analyze the needs in timetable manipulation and to provide a generic organization so that the tool can be used in many structures. The third and final aim is to provide a easy to handle tool which can be used by various user profiles on personal computers with a low processing power.