Hi all, In some recommender applications the system might recommend already consumed items. For example, a hotel recommendation site might recommend hotel A to a user who already stayed at hotel A before.
In order to recommend already consumed items we have to rank all of the items (consumed and unconsumed ones) My problem is how can we rank all the items? Let me explain. If ratings are available I think the problem is easily solved. We can rank all the items because we have both the ratings given by the user and the predicted ratings. However, what should we do if there are no ratings, that is, using Mahout terms we have boolean preferences. Mahout booleanpreferences recommender returns a value for each unconsumed item so that we can rank them. However, we cannot compare these values with the items the user already consumed. Already consumed items have no predicted value. I hope I could explain the problem. Thanks in advance.
