Trust and reputation systems represent a significant trend in decision support for Internet mediated service provision. The basic idea is to let parties rate each other, for example after the completion of a transaction, and use the aggregated ratings about a given party to derive a trust or reputation score, which can assist other parties in deciding whether or not to transact with that party in the future. A natural side effect is that it also provides an incentive for good behaviour, and therefore tends to have a positive effect on market quality. Reputation systems can be called collaborative sanctioning systems to reflect their collaborative nature, and are related to collaborative filtering systems. Reputation systems are already being used in successful commercial online applications. There is also a rapidly growing literature around trust and reputation systems, but unfortunately this activity is not very coherent. The purpose of this article is to give an overview of existing and proposed systems that can be used to derive measures of trust and reputation for Internet transactions, to analyse the current trends and developments in this area, and to propose a research agenda for trust and reputation systems.

Peer-to-peer (P2P) online communities are commonly perceived as an environment offering both opportunities and threats. One way to

Abstract—This paper surveys and analyzes the state of the art of agent-mediated electronic commerce (e-commerce), concentrating particularly on the business-to-consumer (B2C) and business-to-business (B2B) aspects. From the consumer buying behavior perspective, agents are being used in the following activities: need identification, product brokering, buyer coalition formation, merchant brokering, and negotiation. The roles of agents in B2B e-commerce are discussed through the business-to-business transaction model that identifies agents as being employed in partnership formation, brokering, and negotiation. Having identified the roles for agents in B2C and B2B e-commerce, some of the key underpinning technologies of this vision are highlighted. Finally, we conclude by discussing the future directions and potential impediments to the wide-scale adoption of agent-mediated e-commerce. Index Terms—Agent-mediated electronic commerce, intelligent agents. 1

We previously developed a social mechanism for distributed reputation management, in which an agent combines testimonies from several witnesses to determine its ratings of another agent. However, that approach does not fully protect against spurious ratings generated by malicious agents. This paper focuses on the problem of deception in testimony propagation and aggregation. We introduce some models of deception and study how to efficiently detect deceptive agents following those models. Our approach involves a novel application of the well-known weighted majority technique to belief function and their aggregation. We describe simulation experiments to study the number of apparently accurate witnesses found in different settings, the number of witnesses on prediction accuracy, and the evolution of trust networks.

Abstract. The scientific research in the area of computational mechanisms for trust and reputation in virtual societies is a recent discipline oriented to increase the reliability and performance of electronic communities. Computer science has moved from the paradigm of isolated machines to the paradigm of networks and distributed computing. Likewise, artificial intelligence is quickly moving from the paradigm of isolated and non-situated intelligence to the paradigm of situated, social and collective intelligence. The new paradigm of the so called intelligent or autonomous agents and Multi-Agent Systems (MAS) together with the spectacular emergence of the information society technologies (specially reflected by the popularization of electronic commerce) are responsible for the increasing interest on trust and reputation mechanisms applied to electronic societies. This review wants to offer a panoramic view on current computational trust and reputation models.

Virtual organisations (VOs) are composed of a number of individuals, departments or organisations each of which has a range of capabilities and resources at their disposal. These VOs are formed so that resources may be pooled and services combined with a view to the exploitation of a perceived market niche. However, in the modern commercial environment it is essential to respond rapidly to changes in the market to remain competitive.

Abstract. Interactions between entities unknown to each other are inevitable in the ambient intelligence vision of service access anytime, anywhere. Trust management through a reputation mechanism to facilitate such interactions is recognized as a vital part of mobile ad hoc networks, which features lack of infrastructure, autonomy, mobility and resource scarcity of composing light-weight terminals. However, the design of a reputation mechanism is faced by challenges of how to enforce reputation information sharing and honest recommendation elicitation. In this paper, we present a reputation model, which incorporates two essential dimensions, time and context, along with mechanisms supporting reputation formation, evolution and propagation. By introducing the notion of recommendation reputation, our reputation mechanism shows effectiveness in distinguishing truth-telling and lying agents, obtaining true reputation of an agent, and ensuring reliability against attacks of defame and collusion. 1

In this paper, we propose a Bayesian network-based trust model. Since trust is multi-faceted, even in the same context, agents still need to develop differentiated trust in different aspects of other agents ’ behaviors. The agent’s needs are different in different situations. Depending on the situation, an agent may need to consider its trust in a specific aspect of another agent’s capability or in a combination of multiple aspects. Bayesian networks provide a flexible method to present differentiated trust and combine different aspects of trust. A Bayesian network-based trust model is presented for a file sharing peer-to-peer application. 1.

Traditional centralized approaches to security are difficult to apply to large, distributed, multi-agent systems. Developing a notion of trust that is based on the reputation of agents can provide a softer notion of security that is sufficient for many MAS applications. However, designing a reliable and "trustworthy" reputation mechanism is not a trivial problem. In this paper, we address the issue of incentive-compatibility, i.e. why should agents report reputation information and why should they report it truthfully. By introducing a side-payment scheme organized through a set of broker agents we make it rational for software agents to truthfully share the reputation information they have acquired in their past experience. The theoretical results obtained were verified by a simple simulation.

Mobileadhocnetworkshaveinherentlyverydi#erentpropertiestoconventionalnetworks. Thesenewcharacteristics presentmajorsecurityvulnerabilities;inparticular,oneside e#ectoftheuniquewayinwhichroutingprotocolsoperate inadhocnetworksisthatmanynewthreatsarise.Selfishnodesarethosewhichdonotperformcertainopera - tionsthattheprotocolspecifiesthattheyshould,througha wishtoconservepower.Maliciousnodesmaydeliberately disruptthenetworkusingavarietyofattacks.Thispaper discussesreputationmechanismswhichhavebeensuggested asameanstomitigatethedetrimentale#ectofselfishand maliciousnodes.Thispaperrevealsreasonswhycomplex reputationsystemsmaybetooine#cienttouseinamobileadhocnetwork, whereresourcesarelimited.However, suggestionsarealsomadetoshowhowasimplereputation systemmightbeusedtoenhancetherobustnessofadhoc networks.