Reputation plays an important role in multi-agent system. It is a socialized form of trust which makes agent cooperate with each other and reduces the cost of agents' interaction. In a world with only computational trust, the agent can only perceive its own interactions. Its learned trust pattern can only be used by itself. There is no socialized mechanism to magnify the trustworthiness that has been learned. To introduce reputation is the solution to efficiently exploit the trust patterns. If the NTR algorithm is designed for intelligent agents, then the reputation propagation models and reputation generation mechanism are designed for multi-agent systems. Introducing reputation into multi-agent systems brings many benefits: the agent can greatly extend its range of influence to cover other agents. The agent also can share the interaction experience with others. Such sharing will accelerate the washing out of malevolent agents and increase the possibility of transactions for benevolent agents. The reputation will improve the executive efficiency of agents by avoiding unnecessary communication and transactions. In general, reputation is the key to form a tight coupling agent society. There is no acknowledged or standard definition for computational reputation. But it is possible to describe it from five facets: interaction experience, intention of propagation, range of propagation, path of propagation, content of reputation. Interaction experience explains the reputation from the view of information source; intention of propagation explains from the view of agents' motivation; range of propagation explains from the view of spatial consideration; path of propagation explains from the view of network; content of reputation explains from the expression of the reputation. The author builds three models of reputation propagation. Point-to-point based inquiry allows an initiative agent start an inquiry request to its acquaintance. If the middle agent has intention to transfer the inquiry, then the request can be propagated far from the initiative agent and thus form a reputation network. Broadcasting based propagation is to let agent broadcast its experience about every interaction or transaction so that every other agents in the society can learn what happened.
A Trust and Reputation Model as Adaptive Mechanism for Multi-Agent Systems