User modeling is progressively becoming an important and generic component of many applications and services. The mains reasons that explain this phenomenon are the tasks increasing complexity and the wide variety of users.
nformation systems, hypermedia, websites, and application software are becoming more and more complex, hence difficult to use efficiently. Also, the amount of on-line information available to a user through Internet is huge and is still increasing everyday so that recovering information is becoming harder and harder. Finally, together with the huge development of Internet, more and more on-line commercial websites and services are proposed to Internet users. The aim and interest of user modeling consists in these situations in helping the user to efficiently use the systems he is offered and to retrieve the information he is looking for by filtering the information according to his will and needs. Furthermore, while many software, hypermedia, websites and services are potentially used by a variety of users, these systems have been traditionally developed in a “one size fits all” manner. Consequently, they are often not adapted to most of the users, with various knowledge, preferences, and needs. In this context user modeling allows personalizing such systems, their content or presentation, in order to fit the individual.