This book contains most of the papers presented at The Fourth International Conference on Data Mining, held in Rio de Janeiro. The objective of the Conference was to discuss current ideas about data structure which make it possible to analyse and understand the large amounts of information collected by government, business, and scientific applications, and to then develop innovative algorithms and data structures to speed computation. Novel data, text and web mining are among the latest fast emerging application areas which call for the new perspectives and new approaches presented in this volume.