Intuitionistic L-fuzzy Rough Sets, Intuitionistic L-fuzzy Preorders and Intuitionistic L-fuzzy Topologies

In this paper, by constructing an intuitionistic L-fuzzy triangle norm T and an intuitionistic L-fuzzy implicator I, lower and upper approximations of intuitionistic L-fuzzy sets are defined with respect to an intuitionistic L-fuzzy approximation space. Properties of intuitionistic L-fuzzy approximation operators are then given. This paper is devoted to discussing the relationship between intuitionistic L-fuzzy relations and intuitionistic L-fuzzy topologies. It proves that the set of all lower approximation sets based on a reflexive and transitive intuitionistic L-fuzzy relation consists of an intuitionistic L-fuzzy Alexandrov topology; and conversely, an intuitionistic L-fuzzy Alexandrov topology is just the set of all lower approximation sets under a reflexive and transitive intuitionistic L-fuzzy relation. That is to say, there exists a one-to-one correspondence between the set of all intuitionistic L-fuzzy preorders and the set of all intuitionistic L-fuzzy Alexandrov topologies.