How to measure non-specificity of intuitionistic fuzzy sets

In this paper, we address the problem of how to measure non-specificity for intuitionistic fuzzy sets. This problem is relevant to the construction of intuitionistic fuzzy uncertainty measure. Although there already exist many uncertainty measures for intuitionistic fuzzy sets, few of them can discriminate uncertainty degrees of crisp sets. In order to construct a unified uncertainty measure for intuitionistic fuzzy sets, non-specificity must be taken into account. Starting from the Hartley measure, which is related to the cardinality of a crisp set, we propose a non-specificity measure for intuitionistic fuzzy sets. Properties of the proposed non-specificity measure are also investigated. Illustrative examples are employed to show its performance.