Designing an on-line ride-sharing system.

Ride-sharing systems have the potential to match travelers with similar itineraries and time schedules, and to bring significant benefits to individual users and the city as a whole. However, this is a challenging task, since users' requests are not known in advance and they become available a few minutes before departure. In this paper, we design an online ride sharing system, where drivers and passengers send their requests for a ride in advance, possibly on a short notice. Our design is efficient and optimal. This is achieved by dividing the system into two components: the constraint satisfier and the matching module. The constraint satisfier takes as input the spatio-temporal constraints of drivers and passengers and provides feasible (driver, passenger) pairs in real time, and the matching module takes as input the feasible pairs and provides a maximum cardinality matching of drivers and passengers. Our preliminary evaluation shows that the constraint satisfier can resolve the most expensive queries (matching of passenger to en-route drivers) in 2 seconds (on average), while the matching module can achieve a matching ratio of 78% when the offline upper-bound is 80%.