A Definition Of Structured Rough Set Approximations

Pawlak lower and upper approximations are unions of equivalence classes. By explicitly expressing individual equivalence classes in the approximations, Bryniarski uses a pair of families of equivalence classes as rough set approximations. Although the latter takes into consideration of structural information of the approximations, it has not received its due attention. The main objective of this paper is to further explore the Bryniarski definition and propose a generalized definition of structured rough set approximations by using a family of conjunctively definable sets. The connections to covering-based rough sets and Grzymala-Busse's LERS systems are investigated.