This paper makes five contributions to the understanding of the application of recommender systems in E-commerce. First, we examine how traditional marketing methods provided a foundation for the growth of recommender systems as a marketing tool in Ecommerce. Second, we present a taxonomy for Recommender Applications, classifying them based on the inputs to the recommender
process, the method used to generate recommendations, the outputs of the recommendation process to the customer, and the degree of personalization. Third, we examine the patterns that emerge when considering the taxonomy and identify five models of recommender applications. These five models are currently the dominant uses of recommender systems in E-commerce. Fourth, we describe four domains of future study for new recommender system applications based on parts of our taxonomy that have not been adequately explored by the existing applications. Finally, in the appendix, we consider privacy issues that are evolving as more sites begin to implement recommender applications.