What Have the Neighbours Ever Done for Us? A Collaborative Filtering Perspective

  • Authors:
  • Rachael Rafter;Michael P. O'Mahony;Neil J. Hurley;Barry Smyth

  • Affiliations:
  • CLARITY: Centre for Sensor Web Technologies, School of Computer Science and Informatics, University College Dublin, Belfield, Dublin 4, Ireland;CLARITY: Centre for Sensor Web Technologies, School of Computer Science and Informatics, University College Dublin, Belfield, Dublin 4, Ireland;CLARITY: Centre for Sensor Web Technologies, School of Computer Science and Informatics, University College Dublin, Belfield, Dublin 4, Ireland;CLARITY: Centre for Sensor Web Technologies, School of Computer Science and Informatics, University College Dublin, Belfield, Dublin 4, Ireland

  • Venue:
  • UMAP '09 Proceedings of the 17th International Conference on User Modeling, Adaptation, and Personalization: formerly UM and AH
  • Year:
  • 2009

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Abstract

Collaborative filtering (CF) techniques have proved to be a powerful and popular component of modern recommender systems. Common approaches such as user-based and item-based methods generate predictions from the past ratings of users by combining two separate ratings components: a base estimate , generally based on the average rating of the target user or item, and a neighbourhood estimate , generally based on the ratings of similar users or items. The common assumption is that the neighbourhood estimate gives CF techniques a considerable edge over simpler average-rating techniques. In this paper we examine this assumption more carefully and demonstrate that the influence of neighbours can be surprisingly minor in CF algorithms, and we show how this has been disguised by traditional approaches to evaluation, which, we argue, have limited progress in the field.