問53
頻出度★★★
ソフトウェアの品質特性には, 信頼性, 使用性, 効率性, 保守性などがある。ソフトウェアの信頼性について記述したものはどれか。
平成23年度 特別試験 ITパスポート試験 問53
マネジメント系システム開発技術 › システム開発技術
This question's explanation and your answers so far.
解説
問 53
- ア
正解 The correct answer is ア. Reliability is the ability of software to keep performing its required functions under stated conditions for a stated period of time; it is the quality characteristic that expresses how unlikely the software is to fail and how well it holds up when something goes wrong. Choice ア, which says that no abnormal operation occurs even when unexpected data is entered, means that even when the system receives unexpected input such as a user's mistaken entry or an invalid value, it neither stops nor processes the data incorrectly, but stays in a normal state. That is exactly maturity and fault tolerance, the sub-characteristics of reliability. Therefore ア is the statement that describes reliability.
Incorrectイ
Providing a screen interface that is easy for anyone to use describes whether users can understand and operate the software easily, that is, the quality characteristic of usability. Ease of use is a different viewpoint from how unlikely a failure is, so this is not reliability.
Incorrectウ
Obtaining search results within 3 seconds after input is a statement about response time and resource consumption, so it describes efficiency (performance efficiency). It measures whether the software is fast or slow, which differs from reliability, which asks how unlikely an abnormality is.
Incorrectエ
Allowing screens and reports to be changed simply by specifying parameters describes how easy it is to make specification changes or corrections, so it describes maintainability. A structure that can be changed without touching the program itself does raise maintainability, but it does not guarantee that no abnormal operation will occur while the system is running.
ここがポイント
- Do not mix up the four representative software quality characteristics (the JIS X 0129 / ISO/IEC 9126 family): reliability = being unlikely to fail and able to keep functioning even when something goes wrong; usability = being easy to understand and easy to operate; efficiency = response time and resource efficiency; maintainability = being easy to correct and change.
- Concrete examples of reliability include not crashing even when unexpected input arrives, and continuing to process while keeping the damage to a minimum even when a failure occurs. It helps to remember that a choice describing tolerance of abnormal input should be classified as reliability (fault tolerance).
用語