Trust Representation and Aggregation in a Distributed Agent System

Yonghong Wang, Munindar P. Singh

This paper considers a distributed system of software agents who cooperate in helping their users to find services, provided by different agents. The agents need to ensure that the service providers they select are trustworthy. Because the agents are autonomous and there is no central trusted authority, the agents help each other determine the trustworthiness of the service providers they are interested in. This help is rendered via a series of referrals to other agents, culminating in zero or more trustworthy service providers being identified. A trust network is a multiagent system where each agent potentially rates the trustworthiness of another agent. This paper develops a formal treatment of trust networks. At the base is a recently proposed representation of trust via a probability certainty distribution. The main contribution of this paper is the definition of two operators, concatenation and aggregation, using which trust ratings can be combined in a trust network. This paper motivates and establishes some important properties regarding these operators, thereby ensuring that trust can be combined correctly. Further, it shows that effects of malicious agents, who give incorrect information, are limited.

Subjects: 7.1 Multi-Agent Systems; 7.2 Software Agents

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