Formulation and Simplification of Multi-Granulation Covering Rough Sets

The theory of multi-granulation rough sets is one kind of effective methods for knowledge discovery in multiple granular structures. Based on rough sets on a single granular structure, various kinds of multi-granulation rough set models are proposed in the past decades. In this paper, according to two kinds of covering rough sets on single-granulation covering approximation spaces, four types of multi-granulation covering rough set models are defined. Properties of new models are examined in detail, comparison of multi-granulation covering approximation operators is done. Finally, simplification of four types of multi-granulation covering rough sets is investigated.