content attributes [7]. Numerous traditional recommender systems that em-
ploy content-based, knowledge-based, or hybrid approaches in combination with
some multi-attribute preference modeling of users can be found in this category.
Several scoring or utility functions have been developed and used to rank the
candidate items based on users’ content-based preferences, including information
retrieval-based and model-based techniques, such as Bayesian classifiers and various machine learning techniques [4]. More details on these techniques are discussed
in other chapters 3.