Dependable Reactive Event-Oriented Planning

In this paper a knowledge-based event-oriented planner is presented that reasons explicitly about time and a safe reaction in time. By means of a distributed architecture a behaviour is achieved that is capable on one side to use knowledgebased techniques to find good and effective solutions and on the other side it uses procedural knowledge to react immediately on asynchronous events in a technical process and to guarantee so a safe reaction in time. If enough time is available for planning, the procedural component can be “programmed” by the knowledgebased component. The planner operates on explicit knowledge about potential process technologies and constraints about their applicability. To have a high flexibility temporal and causal dependencies are represented separately. Moreover, knowledge about the past and the present that is definite is distinguished from knowledge about the future that may be hypothetical or imperative like scheduled actions or goals. Thus, the planner does not need to replan if unexpected events violate the actual plan. It tries to repair this plan considering all given goals and temporal constraints. However, by explicit reasoning about safety no intermediate plan is generated that result in a dangerous situation without having an emergency action. The technique is illustrated by a railway control and transportation application that is relevant since on one hand it is safety-critical and on the other hand it is so complex that knowledge-based techniques are necessary to master the complexity appropriately. * This paper was submitted to the Data and Knowledge Engineering Journal.