Verification of Quality Requirement Method Based on the SQuaRE System Quality Model ()
1. Introduction
In order to implement or acquiring information system successfully, it is very important to specify the quality requirement and realize the most suitable system product correspond to real customer needs in to the target system product during possible early stage of development.
If we take the wrong approach of quality requirement in accord with the real needs of the customer, it may cause a big loss for a purpose of investment. However, the quality requirements analysis is a very difficult matter because it is non-formulaic and demands much of product customer’s technical perceptiveness, sense in balance and experiences. Traditionally, analysis of quality requirements of a product has been conducted through questionnaires or interviews with customers.
If the result of requirements analysis reveals problems such as miss-predictions /miss-estimation of purpose conformance and/or importance and/or a failure in completeness in the established target system product, customers could not obtain the effectiveness equivalent of investments worth which they truly expect.
Generally, survey items on questionnaires were selected either from previous questionnaires of similar system or based on survey investigator’s personal experience with and preference of product requirements. This kind of lack of structure and incompleteness in the traditional approach introduced missing or biased product requirements and errors in prioritizing requirements to implement in the requirement analysis of a product, resulting in failing to assure the completeness of the quality requirement definition of a product.
On the other hand, we have been working on developing the techniques (SQuaRE) for quality requirements and evaluation for system and software product for a long time in ISO/IEC JTC1 (Joint Technical Committee 1 of the International Organization for Standardization and the International Electro technical Commission) SC7WG 6 (software and systems engineering under ISO technical committee, working group six).
As part of this project, we have also worked on the developments of ISO/IEC9126 and ISO/IEC14598 series, which are the standards to provide supporting technology for above-mentioned works, and also the developments of ISO/IEC25030 quality requirements standards, which was enacted lately for the first time in the world as the standards that assist requirements specifications based on the software and system quality model described in ISO/IEC9126. Currently, the method of quantitative quality requirement definitions based on ISO/IEC9126 quality model that includes six characteristics is widely recognized and used in worldwide for the purpose of specify the quality requirement and evaluation of system/software product. ISO/IEC9126 (This standard has revised to ISO/IEC25010:2011 [4]) defines the six quality characteristics of the system and software. These six quality characteristics are described based on the model of Boehm [5] or McCall [6], or from the view point of a stakeholder’s wide experience, which are considered as necessary and independent from user’s point of view. This model introduced in ISO/IEC9126 was formulated with almost perfect quality target-establishment and evaluation perspective of the system, which covers both structure and completeness based on the hypothesis of a company, even with specific quality target, being “a kind of system”. Through analyzing customer requirements based on these six quality characteristics, it becomes possible to perform complete and objective evaluation of customer quality requirements for a system/software product. Although a certain level of improvement is expected in the completeness of describing product quality objectives by using the ISO/IEC9126 quality model. However, independency among each six quality characteristic is not sure and the suitability of method by using these six quality characteristics for quality requirement is not certified statistically. Ambiguity and lack of verification of the ISO/IEC9126 quality model make it impossible to assure that quality objectives of a product are completely described to satisfy the customer quality requirements.
In recent years, an increasing number of consumers post their reviews on a web-site. This study focuses on negative review of system products posted by consumers, classifies and analyzes such negative reviews based on the six quality characteristics.
For example, an online negative review may relate to a serious concern that affects the operation of the laptop computer, or it may relate to a relatively minor concern that does not affect the operation of the system, but expresses personally preference. In other words, different online negative reviews carry different levels of importance (i.e., different degrees of customer quality requirement). Therefore, the degree of customer dissatisfaction may not be accurately obtained by simply classifying online negative reviews into the six quality characteristics. Above assumption, in this paper, we would like to introduce the concept of quality requirements definition method based on the SQuaRE quality model described in ISO/IEC25030. And, this study verifies the validity of using the six quality characteristics described in ISO/IEC9126, and proposes the result of verification about effectiveness of quantitative quality requirement definition approach from the view point of six quality characteristics described in ISO/IEC9126.
Also, this study used the statistical analysis approach based on the previous study of software process improvement [7].
1.1. Organization of SQuaRE Series
The purpose of the SQuaRE (ISO/IEC25000 [8,9]) series of standards is to assist developing and acquiring system products with the specification of quality requirements and evaluation. Figure 1 shows the organization of the ISO/IEC25000 series of standards.
The SQuaRE includes five core divisions: quality requirements, and quality evaluation, quality management, quality model, quality measurement, as well as extension division. The SQuaRE set of standards supports two main processes i.e. software quality requirements specification and software quality evaluation.
It also provides two main tools such as system/software product quality models and quantitative quality measures in order to support system quality requirements and evaluation processes.
1.2. Concept of Quality Requirement and Evaluation
Figure 2 shows the concept of system/software product quality requirements and evaluations by using SQuaRE series.