Scientific Annals of Computer Science

"Alexandru Ioan Cuza" University of Iaşi

Concurrent Negotiation Protocol for an Elevator Group Controller.

Published in Volume XIII, 2003, p. 79-90, doi:

Authors: Cristian MASALAGIU, Vasile ALAIBA


The temporal logic of actions has been used to specify a concurrent negotiation protocol within a Multi-agent System Controlling a Group of Elevators. This control system, besides real time useful response, must fulfill stability, massive concurrency and correctness requirements. Scheduling a group of elevators is a very difficult real time decision problem. A highly evolved inter-agent negotiation protocol is demanded. We introduce a {em"contract net" like protocol}, enabling an unlimited number of concurrent bidding processes to occur at any time. The decentralized architecture and the uniform distribution of the decision makers allow good behavior even when the most severe breakdown occurs.

It is outside the scope of our work to specify the way the agents are being programmed and also the specification of the proper behavior of the elevators being under control within the system. We focus on proving the consistency of the protocol specification and soundness properties: the protocol does not lead to inter-agent deadlock, every request is completed within a reasonable amount of time and the system is tolerant on failure. We also show that the system is capable of running a theoretically unlimited number of simultaneous requests and also does load-balancing between the agents.

We have used {em temporal logic of actions} to specify the protocol. The actual specification makes use of the TLA+ language, and the various properties of the system were checked with TLC.


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