Trust-Networks in Recommender Systems

Similarity-based recommender systems suffer from significant limitations, such as data sparseness and scalability. The goal of this research is to improve recommender systems by incorporating the social concepts of trust and reputation. By introducing a trust model we can improve the quality and accuracy of the recommended items. Three trust-based recommendation strategies are presented and evaluated against the popular MovieLens [8] dataset

Social Networks and Transactive Memory in Human-Computer Interaction

This study investigates the phenomenon of transactive memory by examining trust networks and social presence in human-computer interaction. Traditional theories suggest that transactive memory can be developed by structural mechanisms that increase knowledge specialization and task coordination, but more recent research also suggests that it can be enhanced through social network mechanisms and close relationships such as trust. In this empirical study, 240 participants were randomly assigned to 3-member teams working on a business- simulation task. The results indicate that dense trust networks had a greater impact on transactive memory than sparse trust networks. When social presence was low, team members in dense trust networks developed greater transactive memory. When social presence was high, team members in sparse trust networks developed greater transactive memory. More reciprocal exchanges were found in teams with dense trust networks, but more negotiated exchanges were found in teams with sparse trust networks

Building Trust Networks

The common agreement in the industry is that the Public Key Infrastructure is complex and expensive. From the year 1976 with the introduction of public key cryptography and the introduction of PKI concept in 1977 a lot of scientific resources has been spent on creation of usable key exchange systems and concepts to build trust networks. Most EU Member States have implemented their own national Public Key Infrastructure solutions mainly to enable strong authentication of citizens. They are however not the only systems within the EU to utilize PKI. Due to the nature of the PKI it is most convenient or suitable in an environment with stakeholders with similar agendas. This has resulted in several new PKI developments for specific purposes, within one industry or one vertical such as healthcare. Some Member States have tried to incorporate vertical needs with an all-purpose PKI solution, such as the Austrian eID card with so called sector specific certificates (http://ec.europa.eu/idabc/en/document/4486/5584). From the CIA (Confidentiality, Integrity, Availability) triangle public key cryptography provides confidentiality and integrity. The modern world however has more requirements in environments where sensitive information is being exchanged. It is not enough to know identity of the entity trying to access the information, but to also know the entity permissions or privileges regarding the requested resource. The authorization process grants the user specific permissions to e.g. access, modify or delete resources. A pure PKI does not allow us to build complex authorization policies, and therefore some of the Member States have built (authentication and) authorization solutions on top of existing authentication infrastructures, especially in the eGovernment sector. The scientific community has also tried to solve this issue by creating extensions to the basic PKI concept, and some of these concepts have been successful. Another problem with large scales systems is the key distribution. Managing a large number of keys using a central solution such as PKI has proven to be problematic in certain conditions. Either there are tradeoffs in security, or problems with application support. The last issue deals with public key cryptography itself. Current cryptography relies on the fact that it provides enough security based on availability of the resources, i.e. computational power. New approaches have been introduced both scientifically and commercially by moving away from the mathematics to other areas such as quantum mechanics. This paper is a quick review on some of the existing systems and their benefits and inherent challenges as well as a short introduction to new developments in the areas of authentication, authorization and key distribution.JRC.G.6-Security technology assessmen

The Design of Trust Networks

One can use trust networks to find trustworthy information, people, products, and services on public networks. Hence, they have the potential to combine the advantages of search, recommendation systems, and social networks. But proper design and correct incentives are critical to the success of such networks. In this paper, I propose a trust network architecture that emphasizes simplicity and robustness. I propose a trust network with constrained trust relationships and design a decentralized search and recommendation process. I create both informational and monetary incentives to encourage joining the network, to investigate and discover other trustworthy agents, and to make commitments to them by trusting them, by insuring them, or even by directly investing in them. I show that making the correct judgments about trustworthiness of others and reporting it truthfully are the optimum strategies since they reward the agents both with information by providing access to more of the network and with monetary payments by paying them for their services as information intermediaries. The extensive income potential from the trust connections creates strong incentives to join the network, to create reliable trust connections, and to report them truthfully

Trust networks for recommender systems

Recommender systems use information about their user’s profiles and relationships to suggest items that might be of interest to them. Recommenders that incorporate a social trust network among their users have the potential to make more personalized recommendations compared to traditional systems, provided they succeed in utilizing the additional (dis)trust information to their advantage. Such trust-enhanced recommenders consist of two main components: recommendation technologies and trust metrics (techniques which aim to estimate the trust between two unknown users.) We introduce a new bilattice-based model that considers trust and distrust as two different but dependent components, and study the accompanying trust metrics. Two of their key building blocks are trust propagation and aggregation. If user a wants to form an opinion about an unknown user x, a can contact one of his acquaintances, who can contact another one, etc., until a user is reached who is connected with x (propagation). Since a will often contact several persons, one also needs a mechanism to combine the trust scores that result from several propagation paths (aggregation). We introduce new fuzzy logic propagation operators and focus on the potential of OWA strategies and the effect of knowledge defects. Our experiments demonstrate that propagators that actively incorporate distrust are more accurate than standard approaches, and that new aggregators result in better predictions than purely bilattice-based operators. In the second part of the dissertation, we focus on the application of trust networks in recommender systems. After the introduction of a new detection measure for controversial items, we show that trust-based approaches are more effective than baselines. We also propose a new algorithm that achieves an immediate high coverage while the accuracy remains adequate. Furthermore, we also provide the first experimental study on the potential of distrust in a memory-based collaborative filtering recommendation process. Finally, we also study the user cold start problem; we propose to identify key figures in the network, and to suggest them as possible connection points for newcomers. Our experiments show that it is much more beneficial for a new user to connect to an identified key figure instead of making random connections

Identification and Inference of Network Formation Games with Misclassified Links

This paper considers a network formation model when links are potentially measured with error. We focus on a game-theoretical model of strategic network formation with incomplete information, in which the linking decisions depend on agents' exogenous attributes and endogenous network characteristics. In the presence of link misclassification, we derive moment conditions that characterize the identified set for the preference parameters associated with homophily and network externalities. Based on the moment equality conditions, we provide an inference method that is asymptotically valid when a single network of many agents is observed. Finally, we apply our proposed method to study trust networks in rural villages in southern India

Coercion, vertical trust and entrepreneurism in bureaucracies: evidence from the Nazi Holocaust

Breton and Wintrobe (1982) develop a non-traditional (modern) model of bureaucratic management that is based on the notion of “vertical trust†– the notion that subordinates “trade services†that advance the goals of the bureau''s leadership in return for various “informal payments,†none of which are codified in formal contracts between the two sets of parties. Applying the model to the Nazi bureaucracy explains how Nazi functionaries, such as Adolf Eichmann, acted as bureaucratic entrepreneurs in accomplishing goals relating to “the Jewish question,†and ultimately “the Final Solution,†for their superiors, such as Adolf Hitler and Heinrich Himmler (Breton and Wintrobe, 1986). As an extension of prior research, the current study examines the hypothesis that the use these vertical trust relationships within the borders of their minor Axis partners (e.g., Hungary) worked more effectively for the Germans than coercion, which would have been required to a greater degree within the borders of occupied European countries (e.g., Holland). Specifically, our estimates suggest that, ceteris paribus, owing to their use of vertical trust networks the minor Axis countries each contributed about 152,000 more European Jews to the Nazi Holocaust apparatus than their German-occupied European country counterparts, wherein the Nazis relied more heavily on coercion.bureaucratic entrepreneurship, vertical trust networks, coercion, statistical decomposition tests

A Network Celebrity Identification and Evaluation Model Based on Hybrid Trust Relation

Trust-based celebrity user identification is the key to the industry\u27s reputation for electronic word of mouth. However, trust and mistrust are independent and coexistent concepts. In this context, we need to consider the existence of the two kinds of user relations brought about by the impact. This paper analyzes the characteristics of trust and distrust in social networks, and gives formal descriptions of trust networks, untrusted networks, and mixed trust networks. Based on the indicators such as degree distribution, correlation coefficient, and matching coefficient, the structural properties of mixed trust networks are studied. Based on the PageRank algorithm, the HTMM metrics affecting users under the mixed trust network environment are proposed. Finally, the validity of HTMM is verified through a real data set containing trust and distrust. Experimental results show that the results of HTMM\u27s celebrity user identification method still have a low level of trust