The sixth type of covering-based rough sets

Rough sets, a tool for data mining, deal with the vagueness and granularity in information systems. For further studies on privacy protection, we study a new type of covering-based rough sets. After presenting their basic properties, this paper explores the interdependency between the lower and upper approximation operations, and condition under which two coverings generate an identical upper approximation operation. Meanwhile this paper explores the relationships among the five types of covering-based rough sets and our new type of covering-based rough sets.