Novelty (in Recommender Systems)
A novel recommendation is one the user did not know about. Offline, novelty is usually approximated from popularity, which is a proxy and not a measurement of what a user knows.
-
-
Diversity (in Recommender Systems)
Diversity is the opposite of similarity, and what counts as similar is a choice. It can be measured inside one list, between users’ lists, or across the whole catalog.