問43
頻出度★★☆
システム開発における設計手順として, 求められる要件を明確にしていく順に並べたものはどれか。
平成25年度 秋期 ITパスポート試験 問43
ストラテジ系システム企画 › 要件定義
This question's explanation and your answers so far.
解説
問 43
- ア
正解 The correct answer is ア, “Business requirements definition, system requirements definition, software requirements definition”. In system development, requirements are made concrete step by step, moving from the broader scope toward the narrower one. (1) Business requirements definition — from the standpoint of management and the user departments, clarify what the business wants to achieve and what outcomes and constraints apply. At this stage it is not yet decided whether the work will be computerized. (2) System requirements definition — building on the business requirements, decide the functions, performance, reliability, security, and so on that are required of the information system as a whole. This is the stage that defines the overall picture, including hardware, software, networks, manual work, and operations. (3) Software requirements definition — carve out the portion of the system requirements that software is responsible for, and work out details such as screens, reports, data, and processing content. Requirements decided at the higher level become the premise for the lower level, so if this order is reversed, what to build ends up being decided first while the purpose of each function is still undetermined. The Common Frame (SLCP) organizes the process in this same flow.
Incorrectイ
Starting from the business requirements definition is correct, but placing the software requirements definition before the system requirements definition is wrong. Software is one part of the whole system; unless it is first decided how much of the work the system as a whole will computerize and what performance and reliability it must have, the scope that software is to cover cannot itself be determined. The higher-level system requirements definition comes first.
Incorrectウ
Placing the system requirements definition before the business requirements definition is wrong. The requirements placed on a system are derived on the basis of what the business wants to achieve (the business requirements). Deciding system requirements while the business requirements are still unsettled results in a system that does not fit the business, and becomes a cause of rework.
Incorrectエ
Placing the business requirements definition last is clearly wrong. The order is almost exactly the reverse of the correct one: it decides what to build (the system and the software) first, and only afterwards thinks about the business purpose. Requirements definition must always start from the purpose of the business.
ここがポイント
- Requirements are defined in the order “business requirements definition → system requirements definition → software requirements definition”, becoming concrete step by step as the scope narrows from broad to narrow (the approach of the Common Frame / SLCP).
- Grasp the difference in roles: business requirements express what the business wants to achieve, from the viewpoint of the user departments and management; system requirements are the demands placed on the information system as a whole, including hardware, software, and operations; and software requirements are the demands on the portion of that system which software handles.
用語