Rating the cost of quality in use for a business system using KAOS model

Stakeholders want quality in use requirements to be satisfied as much as possible to make their life or business activities better than ever. However, some of them should be abandoned if they are expensive. In this paper, we propose a method for analyzing the cost ratio of quality in use for a life or business system during early requirements analysis. This method enables stakeholders to sort out initially required quality in use requirements. The cost depends on the number and the complexity of operations in a system, their data and users. In this method, KAOS model is thus used because it contains goals, operations, users and data. KAOS model also enables us to represent the roles of both human and artificial systems embedded in a business system. When a part of a system should achieve some functional and quality goal, the goal should be transformed into some operations and their data respectively. The relative cost of some function or quality is thus quantified on the basis of operations, data and associations among them. Through the case study, the results of analysis seemed to meet our intuition. In addition, we found the relative cost of quality in use is not so small. This finding makes stakeholders to abandon some of quality in use in this case if they do not have enough budget and/or time.