Multi-Issue Negotiation Protocol with Pre-Domain Narrowing

Abstract

Consensus building among agents is crucial in multi-agent systems because each agent acts independently according to its utility function, and conflict among agents can occur. Therefore, automated negotiation is an essential technology for efficiently resolving conflicts and forming consensuses while also maintaining agents’ privacy. As the domain to be negotiated is large, the computational cost of reaching a consensus increases and the agreement rate decreases. Some negotiation protocols have been proposed wherein a mediator collects the utility information of each agent and creates multiple alternatives of agreements to handle large-scale multi-issue negotiations. However, in such protocols, a limitation is placed on agents’ privacy because all agents have to disclose their private information by following the mediator and pre-decided negotiation rules. In this study, we propose a negotiation protocol with a predomain-narrowing phase to enable efficient negotiations in large-scale domains which can maintain the privacy of information that agents should not disclose to their opponents or the mediator. The proposed protocol divides the negotiation process into a predomain-narrowing phase and the main negotiation phase. In the proposed protocol, the parts subject to negotiation are first narrowed in upon, and then the main negotiation is performed. We also propose two narrowing methods: issue- and option-narrowing. Further, we propose naive agent strategies considering the predomain-narrowing phase. We perform comparative simulation experiments between the baseline negotiation protocol without a domain-narrowing phase and the proposed negotiation protocol with the predomain-narrowing phase. The experimental results show that the proposed protocol achieves higher agreement rates in less negotiation time than the baseline.