Studies 61 the impact of computer models to support policy- making processes in organizations have 62 that client involvement in the model building process is often a 63 for effective model building. One important reason is that the process of model building is frequently more important than the resulting model. Model building itself is largely a 64 process about the problem. Most 65 about the characteristics of an ill-structured problem are gained during the 66 process of designing a computer model, rather than after the model is finished. Another important reason is that most information in an organisation 67 in the mental models of organisation members. To support policy making in organisation it is this knowledge which needs to be 68 and represented in the model. An important topic in client-oriented or 69 model building thus becomes the 70 of relevant knowledge contained in the mental models of participants.