COMPOSITE BOOLEAN SEPARATORS FOR DATA ANALYSIS Peter L. Hammer and Irina I. Lozina Abstract. In [12], we proposed a simple procedure for generating artificial Boolean variables. In this paper, we present a formal description of the procedure and apply the new variables to different problems in machine-learning / data-mining. In particular, we demonstrate the usefulness of these concepts by showing how the introduction of artificial variables can enhance the accuracy of classification systems; we employ the new variables for identifying misclassified observations and examine how deletion of such observations and reversal of their class influence the classification accuracy; we apply the new artificial variables to the attribute selection problem, i.e., to the problem of identifying informative subsets of the original attributes. All the results have been tested on eight publicly available datasets and validated by five well-known machine-learning / data-mining methods.