Towards resource route queries with reappearance

In many routing applications, it is unclear whether driving to a certain destination yields the wanted success. For example, consider driving to an appointment and looking for a parking spot. If there are generally few parking spots in the area or if occupancy of spots is currently high, the search may not be successful. In this case, it is continued, possibly into a different area, where chances of success are higher. We generalize this problem and propose a probabilistic formalization to model the availability of resources (e.g., vacant parking spots) at locations in a road network we refer to as resource locations. Our probabilistic model considers short term observations (observing currently vacant spots) as well as long term observations (average period of vacancy) to adapt to the currently available level of information. Based on this model, we propose a query which is related to probabilistic trip planning queries but has one significant difference: We allow resources that have previously been detected as consumed to reappear. In the above example, this describes the case where somebody vacates a parking spot which has been observed as occupied at an earlier point in time. Therefore, our model allows returning to an already visited resource location if deemed more beneficial than continuing to an unvisited location. As a result, the search space is potentially infinite. We investigate the properties of this problem and propose an efficient, approximative method to solving it.