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Dissertation

Designing and trusting multi-agent systems for B2B applications

01 Jan 2008-
TL;DR: A trust model allowing agents to evaluate the credibility of other peers in the environment using agents' credibility is proposed, which applies a number of measurements in trust evaluation of other party's likely behavior.
Abstract: This thesis includes two main contributions. The first one is designing and implementing B usiness-to-B usiness (B2B ) applications using multi-agent systems and computational argumentation theory. The second one is trust management in such multi-agent systems using agents' credibility. Our first contribution presents a framework for modeling and deploying B2B applications, with autonomous agents exposing the individual components that implement these applications. This framework consists of three levels identified by strategic, application, and resource, with focus here on the first two levels. The strategic level is about the common vision that independent businesses define as part of their decision of partnership. The application level is about the business processes, which are virtually integrated as result of this common vision. Since conflicts are bound to arise among the independent applications/agents, the framework uses a formal model based upon computational argumentation theory through a persuasion protocol to detect and resolve these conflicts. Termination, soundness, and completeness properties of this protocol are presented. Distributed and centralized coordination strategies are also supported in this framework, which is illustrated with an online purchasing case study followed by its implementation in Jadex, a java-based platform for multi-agent systems. An important issue in such open multi-agent systems is how much agents trust each other. Considering the size of these systems, agents that are service providers or customers in a B2B setting cannot avoid interacting with others that are unknown or partially known regarding to some past experience. Due to the fact that agents are self-interested, they may jeopardize the mutual trust by not performing the actions as they are supposed to. To this end, our second contribution is proposing a trust model allowing agents to evaluate the credibility of other peers in the environment. Our multi-factor model applies a number of measurements in trust evaluation of other party's likely behavior. After a period of time, the actual performance of the testimony agent is compared against the information provided by interfering agents. This comparison process leads to both adjusting the credibility of the contributing agents in trust evaluation and improving the system trust evaluation by minimizing the estimation error.

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Citations
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Journal Article
Henry Prakken1
TL;DR: In this paper, the authors investigated to what extent protocols for dynamic disputes, i.e., disputes in which the information base can vary at different stages, can be justified in terms of logics for defeasible argumentation.
Abstract: This article investigates to what extent protocols for dynamic disputes, i.e., disputes in which the information base can vary at different stages, can be justified in terms of logics for defeasible argumentation. First a general framework is formulated for dialectical proof theories for such logics. Then this framework is adapted to serve as a framework for protocols for dynamic disputes, after which soundness and fairness properties are formulated or such protocols relative to dialectical proof theories. It then turns out that certain types of protocols that are perfectly fine with a static information base, are not sound or fair in a dynamic setting. Finally, a natural dynamic protocol is defined for which soundness and fairness can be established.

10 citations

Dissertation
01 Jan 2009
TL;DR: The designing and specification of a trust and contextual information aggregation model, intended to be a reliable alternative to the trust aggregation models already existing, and trying to set apart from those by including rules to emulate human common sense regarding trust building, and mechanisms to obtain a recommendation grade concerning how likely is a potential partner to perform as the authors desire in the fulfilment of a given contract.
Abstract: The study of trust aggregation mechanisms to assist the selection of companies in Business-to-Business systems, is becoming increasingly important to researchers in the areas of Multi-Agent Systems and Electronic Business, because it has been proved that it can provide means to increase the performance and reliability of the existing electronic business communities, by endowing them with human-like social defence mechanisms. The study we present in this document concerns the designing and specification of a trust and contextual information aggregation model, intended to be a reliable alternative to the trust aggregation models already existing, and trying to set apart from those by including rules to emulate human common sense regarding trust building, and mechanisms to obtain a recommendation grade concerning how likely is a potential partner to perform as we desire in the fulfilment of a given contract. This dissertation has three main parts. In the first, we present the trust and contextual information model, showing how we use an S-shaped curve to aggregate the past contract results of a given entity. From there we can retrieve a degree of trust which represents, in an abstract and simplified way, how likely is a given entity to fulfil the next contract, given how well she fulfilled the previous ones. The aggregation of contextual information can act as a disambiguation tool, because the information of the past contracts is treated concerning the context in which they were celebrated, providing, this way, a mean to assess if a given company is the most adjusted to do business with, regarding the specificities of the contract, and independently of how much trust do we deposit in them. In the second part we specify the application that we developed to simulate the process of company selection. This application implements the models that we propose as solution together with a third one, developed by another research group, to compare the performance and utility of our model. We simulate a fabric market, in which a group of buyers needs to buy certain quantities from sellers. In this process, each buyer is going to need the degree of trust and the degree of recommendation for each candidate seller, deciding which one(s) to buy from depending on that information. In the third part we demonstrate and analyze the results that we got from the simulations we have made. We developed three kinds of validation tests for the models: how fast were they identifying the companies violating fewer contracts, how well they react to an abrupt company behaviour change, and how much will the use of a recommendation grade affect the process of selecting a business partner. The results we got from the simulations show that our system for trust and contextual information measure represents a reliable option as a trust aggregation models, since, when compared to other model, it proves to be capable of selecting more times the best business partner, which understandably ends up in fewer violated contracts by the selected seller and higher business utility for the buyer.
References
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Journal ArticleDOI
TL;DR: Fire, a trust and reputation model that integrates a number of information sources to produce a comprehensive assessment of an agent’s likely performance in open systems, is presented and is shown to help agents gain better utility than their benchmarks.
Abstract: Trust and reputation are central to effective interactions in open multi-agent systems (MAS) in which agents, that are owned by a variety of stakeholders, continuously enter and leave the system. This openness means existing trust and reputation models cannot readily be used since their performance suffers when there are various (unforseen) changes in the environment. To this end, this paper presents FIRE, a trust and reputation model that integrates a number of information sources to produce a comprehensive assessment of an agent's likely performance in open systems. Specifically, FIRE incorporates interaction trust, role-based trust, witness reputation, and certified reputation to provide trust metrics in most circumstances. FIRE is empirically evaluated and is shown to help agents gain better utility (by effectively selecting appropriate interaction partners) than our benchmarks in a variety of agent populations. It is also shown that FIRE is able to effectively respond to changes that occur in an agent's environment.

800 citations

Journal ArticleDOI
TL;DR: Four key issues for Web service composition are described, which offer developers reuse possibilities and users seamless access to a variety of complex services.
Abstract: Web service composition lets developers create applications on top of service-oriented computing's native description, discovery, and communication capabilities. Such applications are rapidly deployable and offer developers reuse possibilities and users seamless access to a variety of complex services. There are many existing approaches to service composition, ranging from abstract methods to those aiming to be industry standards. The authors describe four key issues for Web service composition.

770 citations

Journal ArticleDOI
TL;DR: An abstract framework for default reasoning, which includes Theorist, default logic, logic programming, autoepistemic logic, non-monotonic modal logics, and certain instances of circumscription as special cases, is presented and a more liberal, argumentation-theoretic semantics is proposed, based upon the notion of admissible extension in logic programming.

687 citations

Proceedings ArticleDOI
15 Jul 2002
TL;DR: This approach adapts the mathematical theory of evidence to represent and propagate the ratings that agents give to their correspondents and establishes that some important properties of trust are captured by it.
Abstract: For agents to function effectively in large and open networks, they must ensure that their correspondents, i.e., the agents they interact with, are trustworthy. Since no central authorities may exist, the only way agents can find trustworthy correspondents is by collaborating with others to identify those whose past behavior has been untrustworthy. In other words, finding trustworthy correspondents reduces to the problem of distributed reputation management.Our approach adapts the mathematical theory of evidence to represent and propagate the ratings that agents give to their correspondents. When evaluating the trustworthiness of a correspondent, an agent combines its local evidence (based on direct prior interactions with the correspondent) with the testimonies of other agents regarding the same correspondent. We experimentally studied this approach to establish that some important properties of trust are captured by it.

610 citations

Journal ArticleDOI
TL;DR: This article provides a conceptual framework through which the core elements and features required by agents engaged in argumentation-based negotiation, as well as the environment that hosts these agents are outlined, and surveys and evaluates existing proposed techniques in the literature.
Abstract: Negotiation is essential in settings where autonomous agents have conflicting interests and a desire to cooperate. For this reason, mechanisms in which agents exchange potential agreements according to various rules of interaction have become very popular in recent years as evident, for example, in the auction and mechanism design community. However, a growing body of research is now emerging which points out limitations in such mechanisms and advocates the idea that agents can increase the likelihood and quality of an agreement by exchanging arguments which influence each others' states. This community further argues that argument exchange is sometimes essential when various assumptions about agent rationality cannot be satisfied. To this end, in this article, we identify the main research motivations and ambitions behind work in the field. We then provide a conceptual framework through which we outline the core elements and features required by agents engaged in argumentation-based negotiation, as well as the environment that hosts these agents. For each of these elements, we survey and evaluate existing proposed techniques in the literature and highlight the major challenges that need to be addressed if argument-based negotiation research is to reach its full potential.

610 citations