An approach from answer set programming to decision making in a railway interlocking system

Abstract

Railway interlocking systems are apparatuses that prevent conflicting movements of trains through an arrangement of tracks. A railway interlocking system takes into consideration the position of the switches (of the turnouts) and only allows trains to be given clear signals if the routes to be used by the trains are disjoint. There are many different approaches to automate decision making in railway interlocking systems (i.e., to automate supervising that the proposed situation is safe). Meanwhile the classic approaches are offline: only certain routes are allowed and their compatibility is decided in advance, our approaches take the decision on real time, so performance is key. We had previously developed Maple implementations of models based on matrix, algebraic (Grobner bases), logic and logic–algebraic approaches. They are independent from the topology of the layout and can be applied to small or medium size layouts. In this paper another completely new model (also independent from the topology of the layout), that directly translates the decision problem into logic programming, is presented. This new approach directly translates the problem in answer set programming (ASP) style, by defining relations and derived relations, from which the problem is solved using logic techniques inherent to ASP. The main procedure analyses the safety of a proposed situation and an auxiliary procedure returns, if they exist, the sections where a collision could take place. This declarative approach turns out to be much faster and efficient than the previous ones by these authors, and therefore can be applied to much bigger layouts.