レコメンドシステムで、Explicit と Implicit とは

レビューとかでユーザが明示的に評価したら、Explicit。
PVとかCVとかのlogで評価を判断するのがImplicit。らしい。

There are two ways to gather the data. The first method is to ask for explicit ratings from a user, typically on a concrete rating scale (such as rating a movie from one to five stars). The second is to gather data implicitly as the user is in the domain of the system - that is, to log the actions of a user on the site.

Recommendation Systems :: General Collaborative Filtering Algorithm Ideas