Vehicle Routing under Uncertainty

In this thesis, the main focus is on the study of a real-world transportation problem with uncertainties, and on the comparison of a centralized and a distributed solution approach in the context of this problem. We formalize the real-world problem, and provide a general framework to extend it with different sources of uncertainty. We apply computer simulations to compare the two solution approaches, and provide experimental results for three uncertainty types. In release-time uncertainty instances, new orders arrive at random times during the execution of previously planned orders. In service-time uncertainty cases, the time spent by the trucks at pick-up or delivery locations are defined according to a random distribution. In truck-breakdown uncertainty instances, some of the trucks break down at random times. Finally, we also examine cases with different combinations of these uncertainties.Software engineeringElectrical Engineering, Mathematics and Computer Scienc

Multi-Attribute Vickrey Auctions when Utility Functions are Unknown

Multi-attribute auctions allow negotiations over multiple attributes besides price. For example in task allocation, service providers can define their service by means of multiple attributes, such as quality of service, deadlines, or delay penalties. Auction mechanisms assume that the players have evaluation functions over the space of attributes that assign a single value to any combination of attributes. This value (or cost) is directly comparable to price. We argue that in some situations, some of the attributes are difficult to convert to cost, e.g., in transportation it is often important which driver is going to deliver a given truckload. Such personal preferences of a customer are difficult to quantify. To allow negotiations over such non-monetary attributes we relax the requirement of universally comparable utility functions, and give an incentive-compatible auction mechanism that uses only preference orders of the parties and not globally comparable function values. The suggested mechanism assumes that the bidders and the auctioneer have individual total orders over the space of possible contracts, but no utility functions. Each bidder places its bids using its own order, and the winner is chosen by the auctioneer’s order. The actual attribute values are chosen based on the second-best bid. It is shown that this Vickrey intuition yields an incentive-compatible mechanism.Software Computer TechnologyElectrical Engineering, Mathematics and Computer Scienc

Distributed Agent Platform for advanced logistics

Software Computer TechnologyElectrical Engineering, Mathematics and Computer Scienc

Using simulation to evaluate how multi-agent transportation planners cope with truck breakdowns

In most real-world settings, a transportation plan requires modifications during execution. A thorough evaluation of transportation planning methods thus requires testing and comparison in a dynamic environment. We give conditions on a simulation environment that follow from this requirement, and propose a multi-agent simulator meeting these conditions. In addition, we propose a new measure that captures robustness in such dynamic settings. The multi-agent simulator and the robustness measure are then used to compare three different transportation methods (two multi-agent planners and one online optimization approach) in settings with release time uncertainty and truck breakdown incidents.Software Computer TechnologyElectrical Engineering, Mathematics and Computer Scienc

A Qualitative Vickrey Auction

The negative conclusions of the Gibbard-Satterthwaite theorem|that only dictatorial social choice functions are non-manipulable|can be overcome by restricting the class of admissible preference profiles. A common approach is to assume that the preferences of the agents can be represented by quasilinear utility functions. This restriction allows for the positive results of the Vickrey auction and the Vickrey-Clarke-Groves mechanism. Quasilinear preferences, however, involve the controversial assumption that there is some commonly desired commodity or numeraire|money, shells, beads, etcetera|the utility of which is commensurable with the utility of the other alternatives in question. We propose a generalization of the Vickrey auction, which does not assume the agents' preferences being quasilinear but still has some of its desirable properties. In this auction a bid can be any alternative, rather than just a monetary bid. Such an auction is also applicable to situations where no numeraire is available, when there is a fixed budget, or when money is no issue. In the presence of quasilinear preferences, however, the traditional Vickrey turns out to be a special case. In order to sidestep the Gibbard-Satterthwaite theorem, we restrict the preferences of the bidders. We show that this qualitative Vickrey auctions always has a dominant strategy equilibrium, which moreover invariably yields a weakly Pareto efficient outcome.Software Computer TechnologyElectrical Engineering, Mathematics and Computer Scienc