系统分析12课件

第二部系統分析大綱階段工作任務可行性分析擷取系統需求的方法雛型系統法系統需求表達工具-DFD資料字典處理步驟說明系統分析報告階段工作任務初步分析Preliminaryanalysis(又稱可行性分析Feasibilitystudy)目的:1.確認問題2.可行性研究產出:可行性分析報告結果:如可行性不高則系統發展提前結束細部分析Detailanalysis目的:發掘使用者需求產出:系統分析報告結果:作為系統設計階段工作依據可行性分析報告大綱應包含專案背景(回應要求)可行性分析(1.時效2.預算3.技術水準4.人力5.成本效益)結論(如專案可行則有4,5)專案開發時間表要求對方配合事項範例細部分析Detailanalysis工作三步驟擷取系統需求2. 將使用者需求用工具紀錄下來3. 完成一份系統分析報告送交客戶確認(常需要作口頭報告oralpresentation)擷取系統需求的方法擷取系統需求(fact-finding)的方法有4種閱讀公司文件 -目的是要了解作業流程 -有制度的公司會有標準流程與表單 -公司文件不一定與現行作業方式相同 -小公司也會有表單才對

3.問卷 -當想接觸了解系統需求的人數過多時 -優點是時間與成本均較經濟,敏感問題容易得到誠實的答案 -缺點有回收率低,無法經由身體語言判斷回答者是否誠實回答問題,無法即時追問下去等 -問卷一開始需要有一份說明書,明白點出填寫問卷與受訪者的利害關係,以提高填卷意願 -問題分開放式問題與封閉式問題,前者可得到未預期的答案然而不利於統計;後者相反,利於統計但可能限制了回答的內容. -一般以封閉式問題為主,開放式問題為輔面談面談(Interview)是擷取系統需求主要手段面談的問題應包含系統的環境背景系統的功能系統的輸出輸入處理步驟等面談的問題仍開放式問題與封閉式問題兩種.但與問卷不同的是一般以開放式問題為主,封閉式問題為輔面談的地點選擇與時間長短面談時應暖場,問題應從簡易回答的開始

問題本身不應有主觀意見沒有評論也不作承諾面談結束前應對重要問題答案與被面談者再作一次查核面談完後應立即紀錄下來,以免混淆作法----用後丟棄.仍以第三代語言開發----繼續發展成完整系統.(需體認第四代語言的執行

效率不佳的事實)紀錄需求工具常用的紀錄工具有1.資料流程圖(Dataflowdiagram,DFD)2.處理說明(Processdescription,PD)3.資料字典(Datadictionary,DD)資料流程圖(Dataflowdiagram,DFD)一套以圖形表示系統中資料被處理的過程的流程圖圖例資料流(dataflow)處理步驟(process)資料儲存(datastore)資料終端(提供資料或最後得到資訊的個人或單位)第二張DFD稱level-0,表示出系統主要的[處理步驟]和主要的[資料儲存],它是一張[摘要性]強的圖,越往下(level-1,level-2…)越清楚詳細

員工借貸紀錄1.0計算基本工資出席紀錄員工基本工資表2.0計算實際支領4.0印製薪津單3.0印製薪資清單薪資清單個人薪資資料薪津單初步計算結果處理說明

(Processdescription,PD)以文字描述DFD圖中處理步驟的細節如上圖中編號[1.0計算基本工資]的處理說明 1.Gethour-workedofoneemployeefrompersonnel 2.Getthisemployee’sbasicsalaryratefromdatabase 3.Ifthisemployeeisamanagerthenhegetsfixsalary 4.Iftheemployeeisentry-levelworkerthenhissalary=40hour-workedxsalaryrate+(hour-worked-40)xoverworkpayrate 5.Sendouttheresult 6.Processeveryone’srecorduntilendoffile資料字典(Datadictionary,DD)定義資料蒐集過程當中發現的專有名詞作為系統發展工作中的依據圖例說明 身分證號碼=縣市碼+性別碼+7個序號+1個檢查號 基本資料=姓名+性別+身分證號碼+[配偶姓名]+1{電話號碼}3

C.dataelementdefinitioncountycodeformat:onecharactervalue(possiblevalue):A-Lmeaning:AstandsforTaipei,value11whilecalculatingRstandsforTainan,value21whilecalculating……

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