Decision Rules Induced From Sets of Decision Trees

Decision rules belong to known forms of knowledge representation. Among popular measures of their quality length and support can be distinguished. Shorter rules are easier to understand and interpret. Support allows to present patterns hidden in the data. Nowadays, data mining tasks are oriented toward extracting knowledge from data in both distributed and centralized forms. Learning decision rules from a decision tree is a relatively simple task. However, the challenge arises when decision rules are induced from a set of decision trees. Moreover, in the case of distributed data, the decision trees may be constructed independently on different sources, and merging them into a unified set requires resolving conflicts and inconsistencies. In this paper, decision rules are constructed from distributed data based on decision trees induced using the randomly chosen attributes as the splitting criterion. The aim of the study is to compare the quality of two algorithms for constructing rules which are true for a maximum number of trees. The comparison was made based on three factors: the number of trees for which the rule is true, their length and support. Based on performed experiments it was possible to see that the number of true rules for the maximum number of decision trees from the set is greater for algorithm A than for heuristics H. This algorithm allows the induction of shorter rules with greater support compared to heuristic H. However, it should be also noted that the rules induced by heuristic H are often true for a larger number of trees than the rules constructed by algorithm A. Thus, both algorithms can be applied to distributed data.