During the last fifteen years expert systems have successfully been applied to a number of difficult problems in a variety of different application domains. Still, the task of actually developing these systems has been much harder than was predicted, and among systems delivered many have failed to meet user acceptance.

The view taken in this thesis is that many of these problems can be explained in terms ofa discrepancy between the tasks expert systems have been intended for and the kind of situations where they typically have been used. Following recent trends toward more cooperative systems, our analysis shows the need for a shift in research focus from autonomous problem solvers to cooperative advice-giving systems intended to support joint human-computer decision making. The focus of this thesis is on the technical problems involved in realizing the more cooperative form of expert systems.

This thesis examines the task of designing and implementing expert systems that are to be utilised as cooperative decision support and advice-giving systems at workplaces. To this purpose, several commercial case-studies performed over a 10-year period have been utilised together with reported shortcomings of existing expert systems techniques and a review of relevant research in decision-making theory. Desiderata-concerning issues such as cooperation, flexibility, explicitness, knowledge acquisition and maintenance-for an architecture intended to support the implementation of the desired behaviour of cooperative advice-giving systems are formulated, and a system architecture and a knowledge representation intended to meet the requirements of these desiderata is proposed.

The properties of the suggested architecture, as compared to the desiderata, are finally examined, both theoretically and in practice. For the latter purpose the architecture is implemented as the medium-sized system, CONSIDER. The studies performed indicate that the proposed architecture actually possesses the properties claimed. Since the desiderata have been formulated to facilitate the task of building cooperative advice-giving systems for real-world situations, this knowledge should both be useful for practitioners and of enough interest for other researchers to motivate further studies.