Implicator-Conjunctor Based Models of Fuzzy Rough Sets: Definitions and Properties

Abstract

Ever since the first hybrid fuzzy rough set model was pro- posed in the early 1990¿s, many researchers have focused on the definition of the lower and upper approximation of a fuzzy set by means of a fuzzy relation. In this paper, we review those proposals which generalize the logical connectives and quantifiers present in the rough set approxima- tions by means of corresponding fuzzy logic operations. We introduce a general model which encapsulates all of these proposals, evaluate it w.r.t. a number of desirable properties, and refine the existing axiomatic approach to characterize lower and upper approximation operators. © 2013 Springer-Verlag.