3 Vig, J. Sen, S. Riedl, J. 2009 International Conference on Intelligent User Interfaces Sanibel Island, FL 02/08/2009 tagging, recommender systems <p>While recommender systems tell users what items they might like, explanations of recommendations reveal why they might like them. Explanations provide many bene�ts, from improving user satisfaction to helping users make better decisions. This paper introduces tagsplanations, which are explanations based on community tags. Tagsplanations have two key  components: tag relevance, the degree to which a tag describes an item, and tag preference, the user�s sentiment toward a tag. We develop novel algorithms for estimating tag relevance and tag preference, and we conduct a user study exploring the roles of tag relevance and tag preference in promoting effective tagsplanations. We also examine which types of tags are most useful for tagsplanations.</p>