Division charts for handling the consistency in granular computing

Non–deterministic information systems (NISs) have been proposed for handling tables with incomplete information. We have developed algorithms and software tools for calculating criterion values for rules, generating possible equivalence classes and so on for rough sets–based concepts in NISs. In the rough set theory, the concept of consistency can be characterised by inclusion relations between equivalence classes, and this property connects rough sets with granular computing. In the present paper, we propose diagrams that we call division charts for equivalence classes. Division charts present visual information about inclusion relations and consistency. We show how to use division charts to calculate criterion values for rules in NISs, and we also show how they can be used to calculate degrees of data dependencies.