Entropy operator for membership function of uncertain set

Similar to fuzzy set on a possibility space, uncertain set is a set-valued function on an uncertainty space, and attempts to model unsharp concepts. Entropy provides a quantitative measurement of the uncertainty associated with an uncertain set. This paper presents a formula for calculating the entropy of an uncertain set via its inverse membership function. Based on the formula, the entropy operator is shown to satisfy positive linearity property. In addition, this paper proposes a concept of relative entropy to describe the divergence between the membership functions of two uncertain sets.