the research in recommender systems so far has involved ways to improve recommendation accuracy(Adomavicius and Tuzhilin 2005) However, we provide evidence in this thesis that influence is important in recommender systems. We show how we can view relationships between items and people in a recommender system as a social network. It is natural, then, to ask about what the most influential items and users in the system are. Moreover, the knowledge of how to find infuential items and users can enable the system to deliver quality recommendations as the system applies the influence information in various ways, including a) by guiding its members throug the right set of items to evaluate so that the system learns effective user profiles, and b) by selecting reliable users for early evaluations of new items. Influence can be a powerful tool for understanding the workings of recommender systems as well. By investigating how influence forms in a recommender system, we may find strengths and vulnerabilities of the underlying algorithm Broadly speaking, this thesis explores the following: a)the nature of influence in rec ommender systems, b) prior research on influence in other domains and the viability of applying that research to the recommender systems domain, c) new measures of influence based on prior research, extended appropriately for recommender systems, d)the feasibility and implications of meaningful applications of influence. 1 The Problem Domain: Recommender Systems& Collaborative Filtering The advent of the internet has given us far more information than we can handle. For , as of this writing, the blog search engine Technorati tracks more than 63 million blogs, the volunteer-maintained free online encyclopedia wikipedia2 contains more than 1.5 million articles, the reference linking service CrossRef reports to have more than 20 million http://ww Reproduced with permission of the copyright owner. Further reproduction prohibited without permissionReproduced with permission of the copyright owner. Further reproduction prohibited without permission