Dominance-Based Rough Sets Using Indexed Blocks as Granules

Abstract

Dominance-based rough set introduced by Greco et al. is an extension of Pawlak¡¯s classical rough set theory by using dominance relations in place of equivalence relations for approximating sets of preference ordered decision classes satisfying upward and downward union properties. This paper introduces the concept of indexed blocks for representing dominance-based approximation spaces. Indexed blocks are sets of objects indexed by pairs of decision values. In our study, inconsistent information is represented by exclusive neighborhoods of indexed blocks. They are used to define approximations of decision classes. It turns out that a set of indexed blocks with exclusive neighborhoods forms a partition on the universe of objects. Sequential rules for updating indexed blocks incrementally are considered and illustrated with examples.