Witten and Frank 's textbook was one of two books that 1 used for a data mining class in the Fall o f 2001. T h e book covers all major methods o f data mining that p roduce a knowledge representa t ion as output . Knowledge representa t ion is hereby unders tood as a representat ion that can be studied, unders tood, and interpreted by human beings, at least in principle. Thus , neural networks and genetic a lgor i thms are excluded f rom the topics of this textbook. We need to say "can be unders tood in pr inciple" because a large decision tree or a large rule set may be as hard to interpret as a neural network.