Abstract
In the field of rough sets,methods for inducing minimal rules from a given decision table have been proposed. When the decision attribute is ordinal, we may induce rules w.r.t.upper and lower unions of decision classes. This approach would be better in simplicity of obtained rules than inducing rules w.r.t.decision classes directly. However, because of independent applications of rule induction methods, inclusion relations among upper/lower unions in conclusion parts are not inherited to the condition parts of obtained rules. This non-inheritance may debase the quality of obtained rules. In this paper, we propose a few approaches to inherit the inclusion relations among conclusions to the conditions of rules. The performacnes of the proposed approaches are examined by a numerical experiment.
