“…Several incremental hierarchical conceptual clustering systems have been developed recently (Lebowitz, 1986;Fisher, 1987;Hanson & Bauer, 1989;Hadzikadic & Yun, 1989;McKusick & Langley, 1991;Martin & Billman, 1994). Although they differ in many respects (e.g., concept representation, hierarchy evaluation criteria, disjoint versus non-disjoint classes), they usually attack the problem by defining a set of hierarchy-change operators and carrying out a hillclimbing search through the space of possible concept hierarchies aimed at finding a "good" hierarchy (Gennari, Langley, & Fisher, 1989).…”