Use of reason maintenance in model formulation

Studies of the process of model formulation by experts have shown the process to be an iterative one, in which the model is continuously refined until a complete and consistent representation emerges. It is also a highly unstable activity as the problem specifications, including the goal, may change both during and after the formulation. In order to be able to model real world problems, model formulation systems, which provide computer-based support for model formulation, should also be capable of dealing with changes to the problem. This paper presents the architecture of a model formulation system enhanced with reason maintenance capabilities, for dealing with changes in assumptions and specifications during formulation.