A pre-processing data-reduction algorithm for constrained frequent patterns mining. Described in the paper: F. Bonchi, F. Giannotti, A. Mazzanti, D. Pedreschi ExAnte: Anticipated Data Reduction in Constrained Pattern Mining In Proceedings of the 7th European Conference on Principles and Practice of Knowledge Discovery in Databases (PKDD'03) Lecture Notes in Computer Science, Volume 2838, ©Springer. September 22-26, 2003, Cavtat-Dubrovnik, Croatia.