Acknowledgments Writing the acknowledgments is always the nicest part! A lot of people have helped us, and we relish this opportunity to thank them. This book has arisen out of the machine learning research project in the Computer Science Department at the Uni- versity of Waikato, New Zealand. We received generous encouragement and assis- tance from the academic staff members early on in that project: John Cleary, Sally Jo Cunningham, Matt Humphrey, Lyn Hunt, Bob McQueen, Lloyd Smith, and Tony Smith. Special thanks go to Geoff Holmes, the project leader and source of inspira- tion, and Bernhard Pfahringer, both of whom also had significant input into many different aspects of the Weka software. All who have worked on the machine learn- ing project here have contributed to our thinking: We would particularly like to mention early students Steve Garner, Stuart Inglis, and Craig Nevill-Manning for helping us to get the project off the ground in the beginning, when success was less certain and things were more difficult. The Weka system that illustrates the ideas in this book forms a crucial component of it. It was conceived by the authors and designed and implemented principally by Eibe Frank, Mark Hall, Peter Reutemann, and Len Trigg, but many people in the machine learning laboratory at Waikato made significant early contributions. Since the first edition of this book, the Weka team has expanded considerably: So many people have contributed that it is impossible to acknowledge everyone properly. We are grateful to Remco Bouckaert for his Bayes net package and many other contribu-