\input zb-basic \input zb-ioport \iteman{io-port 06089733} \itemau{Mashhoori, Ali; Hashemi, Sattar} \itemti{Incorporating hierarchical information into the matrix factorization model for collaborative filtering.} \itemso{Pan, Jeng-Shyang (ed.) et al., Intelligent information and database systems. 4th Asian conference, ACIIDS 2012, Kaohsiung, Taiwan, March 19--21, 2012. Proceedings, Part III. Berlin: Springer (ISBN 978-3-642-28492-2/pbk). Lecture Notes in Computer Science 7198. Lecture Notes in Artificial Intelligence, 504-513 (2012).} \itemab Summary: Matrix factorization (MF) is one of the well-known methods in collaborative filtering to build accurate and efficient recommender systems. While in all the previous studies about MF items are considered to be of the same type, in some applications, items are divided into different groups, related to each other in a defined hierarchy (e.g. artists, albums and tracks). This paper proposes Hierarchical Matrix Factorization (HMF), a method that incorporates such relations into MF, to model the item vectors. This method is applicable in the situations that item groups form a general-to-specific hierarchy with child-to-parent (many-to-one or many-to-many) relationship between successive layers. This study evaluates the accuracy of the proposed method in comparison to basic MF on the Yahoo! Music dataset by examining three different hierarchical models. The results in all the cases demonstrate the superiority of HMF. In addition to the effectiveness of HMF in improving the prediction accuracy in the mentioned scenarios, this model is very efficient and scalable. Furthermore, it can be readily integrated with the other variations of MF. \itemrv{~} \itemcc{} \itemut{collaborative filtering; hierarchical matrix factorization; matrix factorization; recommender systems} \itemli{doi:10.1007/978-3-642-28493-9\_53} \end