Generating Production Rules from Decision Trees

Many inductive knowledge acquisition algorithms generate classifiers in the form of decision trees. This paper describes a technique for transforming such trees to small sets of production rules, a common formalism for expressing knowledge in expert systems. The method makes use of the training set of cases from which the decision tree was generated, first to generalize and assess the reliability of individual rules extracted from the tree, and subsequently to refine the collection of rules as a whole. The final set of production rules is usually both simpler than the decision tree from which it was obtained, and more accurate when classifying unseen cases. Transformation to production rules also provides a way of combining different decision trees for the same classification domain.