問25
頻出度★★★
次の業務プロセスをDFDで表現したものはどれか。 〔業務プロセス〕 1. 日々の業務において社内各部で発生した伝票を経理担当者が伝票つづりにファイリングする。 2. 決算作業開始時に，ファイリングされた伝票を決算担当者と検算担当者が別々に集計し，両者の結果を照合する。
平成27年度 春期 ITパスポート試験 問25
ストラテジ系システム戦略 › 業務プロセス
This question's explanation and your answers so far.
解説
問 25
- ア
正解 In a DFD, the symbols are used as follows: a circle = a process, two parallel lines = a data store (a place where data is kept), and an arrow = a data flow. Mapping this business process onto the symbols, there are four processes — “File vouchers”, “Settlement person tallies vouchers”, “Verification person tallies vouchers” and “Compare tally results” — and one data store, “Voucher binder”. The flow is: first, in daily operations, the filing process writes vouchers into the voucher binder (the data store); then, at the start of the closing work, the settlement person and the verification person separately tally the vouchers read out of the voucher binder, and those two tally results come together at the comparison process. Choice ア has exactly this shape: an arrow goes from the circle “File vouchers” into the parallel lines “Voucher binder”, the “Voucher binder” branches into the two tallying processes on the left and right, and both merge into “Compare tally results”. Both the assignment of symbols and the direction of the flows match the business procedure, so ア is correct.
Incorrectイ
Here “File vouchers” is drawn with two parallel lines (a data store), while “Voucher binder” is drawn as a circle (a process), so the symbols for the process and the store are swapped. In addition, the flow is a single chain — “Settlement person tallies vouchers” → “File vouchers” → “Verification person tallies vouchers” → “Compare tally results” — in which filing comes after tallying, and it cannot express the parallel structure in which two people tally separately and then their results are compared.
Incorrectウ
“Verification person tallies vouchers” is clearly a process, yet it is drawn with two parallel lines (a data store), while “Voucher binder”, which should be the store, is drawn as a circle. Moreover, the flow runs “tally” → “Compare tally results” → “Voucher binder” → “File vouchers”, so filing happens only after the comparison is finished, which is the reverse of the business procedure of tallying vouchers that have already been filed.
Incorrectエ
“Compare tally results” is drawn with two parallel lines (a data store), so a process is treated as a store, which is wrong. Also, the arrows run “tally” → “Compare tally results” → “Voucher binder” / “File vouchers”, pointing from the comparison result toward filing, so it cannot express the business order in which vouchers are filed first and then tallied.
ここがポイント
- Basic symbols of a DFD (data flow diagram): circle = process, two parallel lines = data store (where data is kept), arrow = data flow, rectangle = external entity (source / sink). Match actions in the business to circles, and storage places such as files or ledgers to the parallel lines.
- When turning a business process into a DFD, narrow down the choices by two checks: (1) whether the symbols are assigned correctly (processes and data stores not swapped), and (2) whether the direction of the data flows matches the chronological order of the business.
用語