Recommender systems provide useful recommendations to a collection of users for items or products that
KEYWORDSRecommender System, Collaborative Filtering, Demographic Filtering, cold start, sparisty scalability
INTRODUCTIONRecommender Systems (RSs) were proposed as a computer-based intelligent techniques whose purpose was to assist with the problem of information overloading. By generating suggestions about new items for a particular user, she/he receive items recommended on basis of their previously purchase records. New users will need to rate appropriate number of items to allow the system to capture their preferences, and thus enable providing reliable recommendations. Thus, the most common form of input for a recommender system is that of ratings of past items. Another type of input is the demographic data regarding the user or item in mind which is usually hard to obtain and is normally collected explicitly from the user or manually from item catalogues [1]. Different techniques have been applied in RS such as Collaborative Filtering (CF)which is considered to be the most successful approach, as it makes its recommendations based on ratings provided by users who are similar to the active user [2]. Collaborative recommendation systems expect a user's interest in new items based on the recommendations of other people with similar interests. CF are classified into two sub-categories: memory-based CF and model-based CF [3]. Memory-based approaches make a prediction by considering the entire collection of previous rated items by a user; examples include User-Based CF algorithms [4]. Model-based approaches learn a model from set of ratings and use this model for providing prediction; examples include item-based CF. Model-based approaches are more scalable than User-Based approaches [5]. Another type of recommender system depends on utilizing demographic attributes of users in order to produce their recommendations with the help of pre-generated demographic clusters.