Contract type sequencing for reallocative negotiation

The capability to reallocate items-e.g. tasks, securities, bandwidth slices, MW hours of electricity, and collectibles-is a key feature in automated negotiation. Especially when agents have preferences over combinations of items, this is highly nontrivial. Marginal cost based reallocation leads to an anytime algorithm where every agent's utility increases monotonically over time. Different contract types head toward different locally optimal task allocations, and contracts from a recently introduced comprehensive contract type, OCSM-contracts, head toward the global optimum. Reaching it can take an impractically long time, so it is important to trade off solution quality against negotiation time. To construct negotiation protocols that lead to the best achievable allocations in a bounded amount of time, we compared sequences of four contract types. Original, cluster, swap, and multiagent contracts. The experiments show that it is profitable to use multiple contract types in the sequence: significantly better solutions are reached, and faster, than if only one contract type is used. However, the best sequences only include original and cluster contracts. Swap and multiagent contracts lead to bad local optima quickly. Interestingly, the number of contracts using any given contract type does not always decrease over time: contracts play the role of enabling further contracts.

[1]  Toru Ishida,et al.  Analyzing the Social Behavior of Contract Net Protocol , 1996, MAAMAW.

[2]  Reid G. Smith,et al.  The Contract Net Protocol: High-Level Communication and Control in a Distributed Problem Solver , 1980, IEEE Transactions on Computers.

[3]  Martin Andersson,et al.  Leveled commitment contracting among myopic individually rational agents , 1998, Proceedings International Conference on Multi Agent Systems (Cat. No.98EX160).

[4]  Tuomas Sandholm,et al.  An Implementation of the Contract Net Protocol Based on Marginal Cost Calculations , 1993, AAAI.

[5]  Tuomas Sandholm,et al.  Contract Types for Satisficing Task Allocation , 1998 .

[6]  Mark S. Fox,et al.  Constraint-Directed Negotiation of Resource Reallocations , 1990, Distributed Artificial Intelligence.

[7]  R. Korf.  An Optimal Admissible Tree Search , 1985 .

[8]  Victor Lesser,et al.  Negotiation among self-interested computationally limited agents , 1996 .

[9]  R. K. Shyamasundar,et al.  Introduction to algorithms , 1996 .

[10]  Victor R. Lesser,et al.  Advantages of a Leveled Commitment Contracting Protocol , 1996, AAAI/IAAI, Vol. 1.

[11]  Eduardo Alonso Fernández,et al.  Rules of encounter: designing conventions for automated negotiation among computers , 1995 .

[12]  Andrew Whinston,et al.  Frontiers of Electronic Commerce , 1996 .

[13]  Hans Akkermans,et al.  Power Load Management as a Computational Market , 1996 .

[14]  Martin Andersson,et al.  Time-Quality Tradeoffs in Reallocative Negotiation with Combinatorial Contract Types , 1999, AAAI/IAAI.

[15]  T. Sandholm.  Limitations of the Vickrey Auction in Computational Multiagent Systems , 1996 .