A Covering-Based Pessimistic Multigranulation Rough Set

In view of granular computing, the classical optimistic and pessimistic multigranulation rough set models are both primarily based on simple granules among multiple granular structures, namely multiple partitions of the universe in MGRS. This correspondence paper presents a new rough set model where set approximations are defined by using multiple coverings on the universe. In order to distinguish Qian's covering-based optimistic multigranulation rough set model, we call the new rough set model as covering-based pessimistic multigranulation rough set model. The key distinction between covering-based pessimistic multigranulation rough set model and Qian's covering-based optimistic multigranulation rough set model is set approximation descriptions. Then some properties are proposed for covering-based pessimistic multigranulation rough set model.