• USER INDEPENDENCE - Content-based recommenders exploit solely ratings
provided by the active user to build her own profile. Instead, collaborative fil
tering methods need ratings from other users in order to find the “nearest neigh-
bors” of the active user, i.e., users that have similar tastes since they rated the
same items similarly. Then, only the items that are most liked by the neighbors
of the active user will be recommended;
• TRANSPARENCY - Explanations on how the recommender system works can be
provided by explicitly listing content features or descriptions that caused an item
to occur in the list of recommendations. Those features are indicators to consult
in order to decide whether to trust a recommendation. Conversely, collaborative
systems are black boxes since the only explanation for an item recommendation
is that unknown users with similar tastes liked that item;
• NEW ITEM - Content-based recommenders are capable of recommending items
not yet rated by any user. As a consequence, they do not suffer from the first-rater
problem, which affects collaborative recommenders which rely solely on users’
preferences to make recommendations. Therefore, until the new item is rated by
a substantial number of users, the system would not be able to recommend it.
Nonetheless, content-based systems have several shortcomings:
• LIMITED CONTENT ANALYSIS - Content-based techniques have a natural limit