1. An apparatus for controlling a recommender system having a processor, said apparatus comprising: a feature-value extractor for analyzing a user profile and for extracting feature-value pairs which characterize a user of said recommender system; a query composer for composing, based on feature-value pairs extracted by said feature-value extractor, a query to be sent to at least one content source; a recommender engine for rating results obtained in response to said query so as to provide a recommendation for said user; and a feature selector for selecting from said feature-value pairs extracted by said feature-value extractor those feature-value pairs which are most discriminative for said user profile, wherein said feature-value extractor is adapted to extract feature-value pairs based on negative user ratings so that queries are composed that exclude results with feature-values corresponding to the negative ratings; and wherein the feature selector is adapted to use the Relief algorithm as a feature selection algorithm for selecting said most discriminative feature-value pairs.