Abstract
The absolute and relative quantifications between the equivalence class and the target concept are the two important research endeavours in rough set theory. Double-quantitative decision-theoretic rough set (Dq-DTRS) models utilise both absolute quantification and relative quantification in their upper and lower approximations to reflect the distinctive degrees of quantitative information. Herein, the authors apply the information theory to Dq-DTRS model to characterise and measure these two types of quantitative information. The expressions of the information entropy with regard to the two quantifications and their corresponding information co-entropy are presented in DqI-DTRS model and DqII-DTRSmodel, respectively. This work makes a further study of Dq-DTRS models by discussing the information measures with respect to absolute and relative quantification.