Multiview Ensemble Method for Detecting Shilling Attacks in Collaborative Recommender Systems

Table 2

Notations and their descriptions.

Notation	Description
	set of the entire users
	set of genuine users in the training set
	set of the entire items
	set of items rated by user u
	rating database, including UserID, ItemID, ratings, and timestamp.
	rating of user u to item i at t moment
	item i is rated by user u at t moment
	item i is not rated by user u at t moment
	the cardinality of the set
	discriminate function, if , the value is 1; otherwise the value is 0