where θ u denotes the currently estimated parameters of the user u and θuz|x,y a
parameter that is estimated using an additional training point (xa, y). Since the goal
of the above criterion is to reduce the uncertainty of which interest groups the target
user belongs to, it favors training points that assign a user to a single interest group.
This approach may not be effective for all models, such as with the aspect model, in
which a user’s preferences are better modeled by considering that a user belongs to
multiple interest groups [23, 25].