Variable precision rough set (VPRS) is an extension of rough settheory (RST). By settingthreshold valueβ,
VPRS looses the strict definition of approximate boundary in RST. Confident threshold value forβis discussed and the
method for deriving decision-making rules from an information system is given by an example. An approach to fuzzy
measures of knowledge is proposed by applying VPRS to fuzzy sets. Some properties of this measure are studied and a pair
of lower and upper approximation operators in fuzzy sets are described. Research results reveal that, based on VPRS,fuzzy
membership functions can be explicitly interpreted and semantics of membership values can be explicitly stated.
Key words: variable precision rough set, fuzzy set, information system, fuzzy measures
