問32
頻出度★★★
ソフトウェア開発モデルの一つであるウォータフォールモデルの記述として, 適切なものはどれか。
平成27年度 春期 ITパスポート試験 問32
マネジメント系ソフトウェア開発管理技術 › 開発プロセス・手法
This question's explanation and your answers so far.
解説
問 32
Incorrectア
A method that moves back and forth between design and programming several times and improves the system through trial and error describes round trip in object-oriented development (an iterative way of going back and forth between design and implementation). The waterfall model is premised on moving in one direction without going back to an earlier stage, so a description of repeatedly going back and forth between stages is the exact opposite.
Incorrectイ
A method that repeats the development process for each subsystem and improves the system while responding to user requirements describes the spiral model (a model that raises the level of completion step by step through iteration). The waterfall model goes through the entire development process only once, so it does not have the characteristic of repeating the process.
- ウ
正解 The correct answer is ウ. The waterfall model is a development model that divides system development into sequential stages (phases) such as “requirements definition → external design → internal design → programming → testing → operation and maintenance”. The deliverables of each stage (documents or programs) are reviewed and approved, and then those deliverables become the input for the next stage. Just as its name comes from the image of water in a waterfall flowing in one direction from top to bottom, it proceeds in order and, in principle, does not go back to an earlier stage. The wording of choice ウ, “divides the system development process into sequential stages, carrying out the work of each later stage based on the deliverables of the preceding stage”, expresses exactly this sequential progression. Because the boundaries between stages are clear, progress management and estimation are easy; on the other hand, be sure to remember its drawback as well: if an error in the requirements is discovered in a later stage, the cost of rework is large.
Incorrectエ
A method that creates a prototype in the early stage of development and determines requirements and specifications while incorporating users' opinions describes the prototyping model. In the waterfall model, the specifications are fixed as documents in the requirements definition stage before moving on to the next stage, so an approach of working out the specifications with a prototype does not apply.
ここがポイント
- Waterfall model = a sequential development model that divides work into stages and moves in one direction to the next stage after the deliverables of the previous stage are approved. Progress and effort are easy to manage, but on the other hand the cost of rework in a later stage is large.
- Key points for telling the main development models apart: sequential with no going back → waterfall; determining requirements with a prototype → prototyping; iterating subsystem by subsystem → spiral; short repeated cycles of design and implementation → agile (iterative).
用語