I'm working with Joonseok Lee on recommendation systems. We improved matrix reconstruction by assuming locality low rank structure based on user-item similarities.
Joonseok Lee, Samy Bengio, Seungyeon Kim, Guy Lebanon and Yoram Singer. Local Collaborative Ranking. Proceedings of the 23rd International World Wide Web Conference (WWW) 2014 (best student paper). pdf
Joonseok Lee, Seungyeon Kim, Guy Lebanon, and Yoram Singer. Local Low-Rank Matrix Approximation. Proceedings of the 30th International Conference on Machine Learning (ICML) 2013. pdf
Joonseok Lee, Mingxuan Sun, Seungyeon Kim, and Guy Lebanon. Automatic Feature Induction for Stagewise Collaborative Filtering. Advances in Neural Information Processing Systems(NIPS) 25, 2012. pdf