Chapter 1 Introduction The Web they sag, is leaving the era of search and entering one of discovery Jeffrey M. O'Brien, Fortune magazine writer Contents 1.1 The Problem Domain: Recommender Systems &e Collaborative Filtering 1.2 Recommender Systems and Influence 1.3 Contributions 1.4 Thesis Roadmap This thesis is about influence in recommender systems. Influence of an entity can be defined as its ability to affect the conduct, behavior, or actions of other entities. Recom mender systems help people find the things they care about from an unmanageably large number of choices by matching up like-minded people. If both of the subjects of influence and recommender systems are familiar to the reader, studying influence in the context of recommender systems might seem a bit out of place at first. The study of influence typically Faust, and Iacobucci 1994), which as the first thing in our mind when we think of recommender systems. Further, most of Reproduced with permission of the copyright owner. Further reproduction prohibited without permissionReproduced with permission of the copyright owner. Further reproduction prohibited without permission