“…As Internet is now a fully integrated part of our society, the use of RSs is becoming increasingly important in a range of areas (Park, Kim, Choi, & Kim, ). For example, RSs play a key role in online stores by highlighting the items that may be more interesting to the user (Sivapalan, Sadeghian, Rahnama, & Madni, ; Wang & Zhang, ), fully personalized online advertising (Bulander, Decker, Schiefer, & Kolmel, ), suggestions on multimedia content (Park, Oh, & Yu, ), content rating sites for tourism, film, research, and many other sectors (Adomavicius & Tuzhilin, ) and in the area on which this work focuses, social networks such as the works published in Lee and Brusilovsky () and in Liu and Aberer (). Because there are many areas to which RSs are applied, multiple mechanisms have also been proposed for the implementation of recommendations.…”