Real-Time Model Checking on Secondary Storage

In this paper, we consider priced-timed automata based exploration for resource-optimal scheduling. Resource-optimal scheduling problems can be seen as an application of real-time model checking in priced domains. State spaces for large problems can easily go beyond the main memory capacity. In this paper, we propose the use of secondary storage devices such as harddisk to store the generated state space induced by priced timed automata. We contribute Iterative Broadening External Breadth-First Branch-and-Bound that stores each breadth-first level on the harddisk. The algorithm achieves its completeness by trying to find an upper bound on the optimal solution in an incomplete search tree. Iteratively, the upper bound is made tighter and the coverage of the search space is increased. We present correctness and completeness proofs for the suggested algorithm along with experimental results on different instances of aircraft landing scheduling to validate the practicality of our approach.