Propagation Models for Trust and Distrust in Social Networks

Semantic Web endeavors have mainly focused on issues pertaining to knowledge representation and ontology design. However, besides understanding information metadata stated by subjects, knowing about their credibility becomes equally crucial. Hence, trust and trust metrics, conceived as computational means to evaluate trust relationships between individuals, come into play. Our major contribution to Semantic Web trust management through this work is twofold. First, we introduce a classification scheme for trust metrics along various axes and discuss advantages and drawbacks of existing approaches for Semantic Web scenarios. Hereby, we devise an advocacy for local group trust metrics, guiding us to the second part which presents Appleseed, our novel proposal for local group trust computation. Compelling in its simplicity, Appleseed borrows many ideas from spreading activation models in psychology and relates their concepts to trust evaluation in an intuitive fashion. Moreover, we provide extensions for the Appleseed nucleus that make our trust metric handle distrust statements. Cai-Nicolas Ziegler is a post-doctoral researcher at DBIS, the Databases and Information Systems group of the University of Freiburg, Germany. He studied Computer Science at the University of Passau, Germany, and Université Laval, Québec, receiving his Diploma (equivalent to MSc) in 2003. Cai-Nicolas obtained his PhD in Computer Science from the University of Freiburg in 2005. His primary research interests cover collaborative filtering applications and recommender systems, as well as computational trust models on the verge of human-computer interaction. Georg Lausen is head of the research group on Databases and Information Systems (DBIS) at the University of Freiburg, Germany. He received his Diploma in Industrial Engineering in 1978, PhD in 1982, and his postdoctoral lecture qualification (Habilitation) in 1985 from the University of Karlsruhe (TH). He was associate professor for Information Technology and Integration Problems at the Technical University of Darmstadt from 1986 to 1987. From 1987 to 1994 he was full professor for databases and informations systems at the University of Mannheim, and since 1994 at the University of Freiburg. His current research interests comprise information integration, internet technologies, and Web services.     

基于主观信任协作的信任评估模型

以开放式网络中主观信任为研究背景,提出了一个完整的信任评估模型,给出了合理的直接信任和推荐信任评估具体计算公式及相关的其他解决办法,解决了主体间信任的评估。通过仿真实验的研究与分析,进一步验证了该信任评估模型的可行性与合理性。     

基于概率的信任传播模型

社会网络中,用户之间的信任关系可以为用户判别信息是否可信提供依据。现有的信任计算方法一般是通过搜索节点之间的路径,再在其上添加各种其它限制,如路径长度、信任度下界等来计算信任度,而考虑节点之间的相似性的方法却很少。从节点之间的相似性出发,在信任传播模型的基础上,结合贝叶斯条件概率公式,提出了基于概率的信任传播模型。同时分析了信任传播模型中衰减系数对结果的影响;通过统计分析数据,得出具有信任关系的用户之间的相似度要比不具有信任关系的用户之间的相似度高得多,从而证明了贝叶斯理论可显著提高信任传播算法的有效性。在Epinion数据集上进行的实验证明了该方法的有效性。     

Towards content trust of web resources

Trust is an integral part of the Semantic Web architecture. Most prior work on trusts focuses on entity-centered issues such as authentication and reputation and does not take into account the content, i.e., the nature and use of the information being exchanged. This paper defines content trust and discusses it in the context of other trust measures that have been previously studied. We introduce several factors that users consider in deciding whether to trust the content provided by a Web resource. Our goal is to discern which of these factors could be captured in practice with minimal user interaction in order to maximize the quality of the system's trust estimates. We present results on a study to determine which factors were more important to capture, and describe a simulation environment that we have designed to study alternative models of content trust.     

An analysis of the exponential decay principle in probabilistic trust models

Research in models for experience-based trust management has either ignored the problem of modelling and reasoning about dynamically changing principal behaviour, or provided ad hoc solutions to it. Probability theory provides a foundation for addressing this and many other issues in a rigorous and mathematically sound manner. Using Hidden Markov Models to represent principal behaviours, we focus on computational trust frameworks based on the ‘beta’ probability distribution and the principle of exponential decay, and derive a precise analytical formula for the estimation error they induce. This allows potential adopters of beta-based computational trust frameworks and algorithms to better understand the implications of their choice.     

A survey of trust in computer science and the Semantic Web

Trust is an integral component in many kinds of human interaction, allowing people to act under uncertainty and with the risk of negative consequences. For example, exchanging money for a service, giving access to your property, and choosing between conflicting sources of information all may utilize some form of trust. In computer science, trust is a widely used term whose definition differs among researchers and application areas. Trust is an essential component of the vision for the Semantic Web, where both new problems and new applications of trust are being studied. This paper gives an overview of existing trust research in computer science and the Semantic Web.     

Trust establishment in the formation of Virtual Organizations

Virtual Organizations (VOs) represent a new collaboration paradigm in which the participating entities pool resources, services, and information to achieve a common goal. VOs represent an interesting approach for companies to achieve new and profitable business opportunities by being able to dynamically partner with others. Thus, choosing the appropriate VO partners is a crucial aspect. Ensuring trustworthiness of the members is also fundamental for making the best decisions. In this paper, we show how trust negotiation represents an effective means to select the best possible members during different stages in the VO lifecycle. We base our discussion on concrete application scenarios and illustrate the tools created by us that integrate trust negotiation with a VO Management toolkit.     

基于云环境下的信任管理模型研究

针对云计算环境中服务节点的可信度参差不齐常导致用户很难获得高质量组合服务的问题,本文研究和分析了几种经典的信任模型,并在此基础上构建了一个云计算环境下信任模型的体系结构。该系统主要由信任引擎和验证引擎组成,通过该系统用户可以得到潜在的合作伙伴列表,然后从中选择服务评价最高者来为自己提供服务。     

Factors affecting members' trust belief and behaviour intention in virtual communities

In this research we investigate whether antecedent factors of participant trust and institutional trust significantly influence members' trust belief towards virtual communities. Further, we investigate how members' trust levels affect their behaviour intention. A model of factors that affect members' trust in virtual communities is constructed. We analysed 625 valid online questionnaires obtained from virtual communities related to travel, games, and computer information. The findings suggest that benefit attraction and shared value have significant positive effects on building participant trust, and monitoring has a significant positive effect on building institutional trust. Trust building influences both members' stickiness in virtual communities and their willingness to share information. This research suggests that the extent to which members trust community-based website environments significantly influences their practical behaviour in such environments.     

Attention web designers: You have 50 milliseconds to make a good first impression!

Three studies were conducted to ascertain how quickly people form an opinion about web page visual appeal. In the first study, participants twice rated the visual appeal of web homepages presented for 500 ms each. The second study replicated the first, but participants also rated each web page on seven specific design dimensions. Visual appeal was found to be closely related to most of these. Study 3 again replicated the 500 ms condition as well as adding a 50 ms condition using the same stimuli to determine whether the first impression may be interpreted as a 'mere exposure effect' (Zajonc 1980). Throughout, visual appeal ratings were highly correlated from one phase to the next as were the correlations between the 50 ms and 500 ms conditions. Thus, visual appeal can be assessed within 50 ms, suggesting that web designers have about 50 ms to make a good first impression.     

一种在网格中信任评估机制

在一个面向服务的网格结构中,服务之间的信任关系很难建立,这是因为一方面要支持单次登录机制(SSO);另一方面还要支持大量的动态临时服务信任的交互,源端和目的端不可能提前建立信任关系,这样源端无法提前评估对目的的信任,因此应该研究评估S对T信任的解决方法。本文基于委托图的传递闭包特点来评估参与者的信任。     

Modeling individual trust development in computer mediated collaboration: A comparison of approaches

This research models and investigates individual trust development over time in computer mediated collaboration. Risk, benefit, utility value, effort, power and interest are six factors that influence individual trust development. This paper introduces two new approaches, the scale balance model and the trust spider diagram, to help model and investigate individual trust development over time. A 2 year longitudinal case study is used to investigate individual trust development based on a yearlong student project. 16 student groups participated in the computer mediated collaboration. Survey data were collected at three points throughout the project year and the results are analyzed using the two approaches. Interviews were also conducted at the end of the project. In this research, interesting findings, such as some dynamic features, are revealed by using the methods. Each approach to analyzing individual trust development has its strengths and weaknesses, and using the two together has the benefit of mitigating some weaknesses and combining the strengths. Analyzing trust development over time contributes to enhance computer mediated collaboration in both theoretical research and practical application.     

开放网络中基于群组的主观信任模型

针对现有信任模型不能很好地解决信任信息有效共享问题.从模拟人类社会信任建立过程出发,提出了开放网络中基于群组的信任模型,并给出了信任初始化算法以及对自私节点和不诚实节点的惩罚机制.最后,通过仿真实验验证模型能够有效地收集推荐信息,同时减少恶意推荐对信任合成的影响.     

一个含有信任度的反馈式信任管理模型的设计

提出了一种含有反馈的信任管理模型,将信任度结合到信任管理中,模型具有自主学习反馈的功能,能够将自己及别人的经验融入系统,使系统在学习中不断得到修正完善。通用、灵活、自动学习是本模型的特点。     

TRAVOS: Trust and Reputation in the Context of Inaccurate Information Sources

In many dynamic open systems, agents have to interact with one another to achieve their goals. Here, agents may be self-interested, and when trusted to perform an action for another, may betray that trust by not performing the action as required. In addition, due to the size of such systems, agents will often interact with other agents with which they have little or no past experience. There is therefore a need to develop a model of trust and reputation that will ensure good interactions among software agents in large scale open systems. Against this background, we have developed TRAVOS (Trust and Reputation model for Agent-based Virtual OrganisationS) which models an agent’s trust in an interaction partner. Specifically, trust is calculated using probability theory taking account of past interactions between agents, and when there is a lack of personal experience between agents, the model draws upon reputation information gathered from third parties. In this latter case, we pay particular attention to handling the possibility that reputation information may be inaccurate.     

一种新的基于网格环境的行为信任模型

针对目前网格环境下资源管理和分配中所存在的安全问题,提出了一种新的基于实体行为的信任管理模型.着重描述了行为信任的定义和算法说明,实验和分析结果表明,与以往的信任模型相比,这种信任模型能更加精确地评估实体之间的信任关系,从而能更加有效地解决网格环境中存在的安全问题.     

On-line trust: concepts, evolving themes, a model

Trust is emerging as a key element of success in the on-line environment. Although considerable research on trust in the offline world has been performed, to date empirical study of on-line trust has been limited. This paper examines on-line trust, specifically trust between people and informational or transactional websites. It begins by analysing the definitions of trust in previous offline and on-line research. The relevant dimensions of trust for an on-line context are identified, and a definition of trust between people and informational or transactional websites is presented. We then turn to an examination of the causes of on-line trust. Relevant findings in the human–computer interaction literature are identified. A model of on-line trust between users and websites is presented. The model identifies three perceptual factors that impact on-line trust: perception of credibility, ease of use and risk. The model is discussed in detail and suggestions for future applications of the model are presented.     

一种基于本体映射处理推荐信任信息的模型

在高动态、开放、异质和分布式网络环境下,在线实体不可避免地需要在交互之前考虑其潜在合作伙伴的可信程度.由于实体通常不具备关于这些潜在合作伙伴的足够知识,因此从所谓第三方收集一些推荐信任信息是必要而且重要的.然而,由于目前没有关于信任的一致理解,推荐信任信息很难被实体理解和使用.信任本体的出现有助于解决这个问题,从而促进互操作性.但在实际上,目前仍没有一个可被所有实体全局共享的信任本体.提出一个采用本体映射来促进推荐信任信息理解的模型,该模型实现了基于不同信任本体的各参与方的有效交互,提高了在线环境中信任管理的灵活性、开放性和可扩展性.     

基于模糊聚类的信任类型动态定义机制研究

从主观信任的本质出发,提出了基于Agent的主观信任协作模型,分析了主体信任协作关系的本质;引入模糊集台理论的隶属度概念,以信任向量的形式对主观信任进行定量的描述,解决了主观信任的建模问题;结合主观信任协作模型,引入模糊聚类理论,提出了基于模糊聚类的信任类氆动态定义机制,为各主体之间的信任评估提供了依据。     

基于时态逻辑的可信平台信任链建模

针对可信计算中信任链理论缺乏深入分析验证的现状,分析了信任链理论中,可信与信任的内涵及其隐含的动态特性,借助时态逻辑的时间推理能力,建立了可信平台中的信任链的形式化模型,依据该模型,观察信任传递的过程,从而从理论上验证了信任在信任链上的可传递性,并得出信任在信任链上传递的充分条件.