問41
頻出度★★★
ファンクションポイント法に関する記述はどれか。
平成21年度 春期 ITパスポート試験 問41
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 41
- ア
正解 Function Point analysis (the FP method) estimates the scale of software by counting the number of functions that the software provides to its users. Specifically, you identify five kinds of functions — external inputs, external outputs, external inquiries, internal logical files, and external interface files — then weight each count according to its difficulty and add them up to obtain the function point value. Its distinguishing feature is that it counts the functions the user can see (screens, reports, files) rather than how the software is built, such as the number of lines of source code. It is therefore not easily affected by the programming language or the implementation method, and an estimate can be made even at an early stage such as requirements definition. Hence ア, which describes a method that estimates software scale based on the number of functions the software has, is the correct answer.
Incorrectイ
Measuring scale from the number of program lines (LOC) or the file size is a description of the LOC method (program step method). The line count varies greatly depending on the programming language and on how each developer writes code, and it is hard to know before coding begins — these are its weaknesses. Function Point analysis was devised to make up for them by counting functions instead of lines, so イ is in fact the method that FP analysis is contrasted with.
Incorrectウ
Deriving optimistic and pessimistic values from the estimator's experience describes estimation techniques that rely on experience and subjective judgement, such as three-point estimation (a PERT-style estimate using optimistic, most likely, and pessimistic values). Function Point analysis follows a quantitative procedure of counting functions and weighting them, so it differs from ウ, which starts from the estimator's intuition and accumulated experience.
Incorrectエ
A method that multiplies the expected number of program lines by correction factors such as engineer capability and requirement reliability in order to obtain development effort, duration, staffing, and productivity is a description of COCOMO (COnstructive COst MOdel). Because its starting point is the expected line count, it is not the FP method but a line-count-based estimation model.
ここがポイント
- Function Point analysis estimates scale by counting the user-visible functions — external inputs, external outputs, external inquiries, internal logical files, and external interface files — and weighting them. Its advantages are that it does not depend on the implementation language and that it can be applied even at an early stage of development.
- Keep the estimation methods straight: based on the line count = the LOC method (program step method); multiplying the line count by correction factors to get effort = COCOMO; setting optimistic and pessimistic values from experience = three-point estimation; based on the number of functions = Function Point analysis.
用語