User Preference Sources: Explicit vs. Implicit Feedback

The process of collecting preferences from users is fundamental during the normal operational life of a recommender system. The preference elicitation strategy can affect both the “user utility” (how well the system can make good recommendations to the new user who is undergoing the elicitation process) and the “system utility” (how well the system can provide good recommendations to all users, given what it learns from the new users). Not only do recommender systems need to gather information from users; they also need this information to be reliable and noiseless, as inconsistencies in user preferences limit prediction accuracy. This chapter provides an overview of several design criteria for making the elicitation process more effective. The chapter analyzes two sources of preferences: (i) implicit feedbacks, inferred from the observable user activity, such as purchases or clicks; and (ii) preferences the user has explicitly stated for particular items.