Recommendation tools are now a common component in many online sites which involve a user choosing to view or purchase items based on personal preferences. For example, books, movies, music, hotels, restaurants, etc.
Collaborative Filtering techniques are one approach to recommendation. These techniques use the previous preferences of users to recommend new items to a user.
Despite the prevalence of recommendation techniques, the area still remains a fruitful research one, from the perspectives of data available, approaches and techniques used and the analysis of the usefulness and novelty of recommendations, and many others.