Abstract:
In recommender systems user preferences can be fairly dynamic, as users tend to exploit a wide range of items and modify their tastes accordingly over time. In this paper...Show MoreMetadata
Abstract:
In recommender systems user preferences can be fairly dynamic, as users tend to exploit a wide range of items and modify their tastes accordingly over time. In this paper, we model user-item interactions over time using a tensor that has time as a dimension (mode). To account for the fact that user preferences change individually, we propose a new measure of user-preference dynamics (UPD) that captures the rate with which the current preferences of each user have been shifted. UPD shows the variability in how users interact with items in recommender systems. We generate recommendations based on a tensor factorization technique, where the importance of past user preferences are weighted according to their UPD values, that is, higher UPD values downweigh more past user preferences. Additionally, we exploit users' side data, such as demographics, which improve the accuracy of recommendations based on a coupled tensor-matrix factorization scheme. Our empirical evaluation uses two real benchmark datasets from the social media platforms Last.fm and MovieLens, containing users' history records pertaining to listening to songs and viewing movies, respectively. We demonstrate that in both datasets, there are users with a varying level of dynamics, expressed by the UPD metric. Our experimental results show that the proposed method outperforms several baselines, by taking into account both dynamics and side data of users.
Published in: IEEE Transactions on Systems, Man, and Cybernetics: Systems ( Volume: 46, Issue: 6, June 2016)

Department of Computer Science, University of Cyprus, Nicosia, Cyprus
Department of Informatics, Aristotle University of Thessaloniki, Thessaloniki, GR, Greece
Dimitrios Rafailidis was born in Larisa, Greece, in 1982. He received the B.Sc., M.Sc., and Ph.D. degrees from the Department of Informatics of the Aristotle University of Thessaloniki, Thessaloniki, Greece, in 2005, 2007, and 2011, respectively.
He is a Post-Doctoral Research Fellow with the Department of Informatics, Aristotle University of Thessaloniki and the Department of Computer Science, University of Cyprus, Nicosi...Show More
Dimitrios Rafailidis was born in Larisa, Greece, in 1982. He received the B.Sc., M.Sc., and Ph.D. degrees from the Department of Informatics of the Aristotle University of Thessaloniki, Thessaloniki, Greece, in 2005, 2007, and 2011, respectively.
He is a Post-Doctoral Research Fellow with the Department of Informatics, Aristotle University of Thessaloniki and the Department of Computer Science, University of Cyprus, Nicosi...View more

School of Management, Catholic University of Eichstät-Ingolstadt, Ingolstadt, Germany
Alexandros Nanopoulos received the B.Sc. and Ph.D. degrees from the Department of Informatics of the Aristotle University of Thessaloniki, Thessaloniki, Greece, in 1997 and 2003, respectively.
He was a Lecturer with the Department of Informatics, Aristotle University of Thessaloniki, from 2004 to 2008. He was an Assistant Professor with the University of Hildesheim, Hildesheim, Germany, from 2008 to 2013. He is currently a...Show More
Alexandros Nanopoulos received the B.Sc. and Ph.D. degrees from the Department of Informatics of the Aristotle University of Thessaloniki, Thessaloniki, Greece, in 1997 and 2003, respectively.
He was a Lecturer with the Department of Informatics, Aristotle University of Thessaloniki, from 2004 to 2008. He was an Assistant Professor with the University of Hildesheim, Hildesheim, Germany, from 2008 to 2013. He is currently a...View more

Department of Computer Science, University of Cyprus, Nicosia, Cyprus
Department of Informatics, Aristotle University of Thessaloniki, Thessaloniki, GR, Greece
Dimitrios Rafailidis was born in Larisa, Greece, in 1982. He received the B.Sc., M.Sc., and Ph.D. degrees from the Department of Informatics of the Aristotle University of Thessaloniki, Thessaloniki, Greece, in 2005, 2007, and 2011, respectively.
He is a Post-Doctoral Research Fellow with the Department of Informatics, Aristotle University of Thessaloniki and the Department of Computer Science, University of Cyprus, Nicosia, Cyprus. His current research interests include databases, multimedia information retrieval, social media mining, and parallel and cloud computing.
Dimitrios Rafailidis was born in Larisa, Greece, in 1982. He received the B.Sc., M.Sc., and Ph.D. degrees from the Department of Informatics of the Aristotle University of Thessaloniki, Thessaloniki, Greece, in 2005, 2007, and 2011, respectively.
He is a Post-Doctoral Research Fellow with the Department of Informatics, Aristotle University of Thessaloniki and the Department of Computer Science, University of Cyprus, Nicosia, Cyprus. His current research interests include databases, multimedia information retrieval, social media mining, and parallel and cloud computing.View more

School of Management, Catholic University of Eichstät-Ingolstadt, Ingolstadt, Germany
Alexandros Nanopoulos received the B.Sc. and Ph.D. degrees from the Department of Informatics of the Aristotle University of Thessaloniki, Thessaloniki, Greece, in 1997 and 2003, respectively.
He was a Lecturer with the Department of Informatics, Aristotle University of Thessaloniki, from 2004 to 2008. He was an Assistant Professor with the University of Hildesheim, Hildesheim, Germany, from 2008 to 2013. He is currently an Assistant Professor with the Catholic University of Eichstaett-Ingolstadt, Ingolstadt, Germany. His current research interests include machine learning, data mining, and Web information retrieval. He has coauthored over 120 articles in international journals and conference proceedings.
Alexandros Nanopoulos received the B.Sc. and Ph.D. degrees from the Department of Informatics of the Aristotle University of Thessaloniki, Thessaloniki, Greece, in 1997 and 2003, respectively.
He was a Lecturer with the Department of Informatics, Aristotle University of Thessaloniki, from 2004 to 2008. He was an Assistant Professor with the University of Hildesheim, Hildesheim, Germany, from 2008 to 2013. He is currently an Assistant Professor with the Catholic University of Eichstaett-Ingolstadt, Ingolstadt, Germany. His current research interests include machine learning, data mining, and Web information retrieval. He has coauthored over 120 articles in international journals and conference proceedings.View more