Critical Review of Z-numbers: The theoretical and application development

As one of the established concepts in fuzzy set theory, Z-numbers have demonstrated its fundamental advantages regarding reliability aspects that have been ignored in existing research. Based on a simple systematic review of the literature, this paper aims to discover the issues in the development of the theoretical and application of Z-numbers. According to the review, several issues associated with the theoretical development of Z-numbers have been identified, including the complexity of the computation process, reduction of informativeness level of results, and measure of uncertainty. Furthermore, one of the issues in the application of Z-numbers is the conversion process of Z-numbers to actual fuzzy numbers, where it is critical to keep the process simple while avoiding data loss. However, this issue in theoretical development is expected to be resolved by improving the element of Z-numbers, integrating Z-numbers with other approaches, and proposing techniques to compute the uncertainty of Z-numbers. Meanwhile, Z-information and the aggregation method were utilized and improved to overcome the issue in the application development of Z-numbers. The findings of this review will enable future researchers to gain a better understanding of Z-numbers' issues.