Software Engineering for Digital Home 單元 2 ：軟體處理程序與需求分析 2-2 軟體需求 Presenter: Away

Software Engineering for Digital Home 2 Outline Introduction Functional vs. nonfunctional requirementsFunctionalnonfunctional Requirements elicitation activities –Identifying actors and scenariosIdentifying actors and scenarios –Identifying use case –Refining use case and identifying relationship –Identifying nonfunctional requirementsIdentifying nonfunctional requirements Software Requirements Specifications

Software Engineering for Digital Home 3 Software life cycle Development cycle Introduction Design ImplementationTesting Maintenance Requirements Engineering Requirements Elicitation System design Object designAnalysis Use CasesProblem statementClass diagram

Software Engineering for Digital Home 4 Requirements engineering Analysis Problem statement Requirements elicitation Nonfunctional requirements Dynamic model Analysis object model Function model (Use case) Analysis Model Specification Requirements

Software Engineering for Digital Home 5 Requirements elicitation Requirements elicitation focuses on describing the purpose of the system. (Requirements elicitation 重點集中於描述系統目的 ) During Requirements elicitation to produce a requirements specification. ( 完成 requirements elicitation 流程後會產出一份系統需求規格書 ) The requirements specification is written in natural language. ( 系統需求規格書是以人類熟析的語言撰寫 ) The requirements specification is structured and formalized during analysis to produce an analysis model. ( 完成 analysis 流程後產出的 analysis model 是根據 requirements specification 而來 ) Requirements elicitation and analysis occur concurrently and iteratively. (Requirements elicitation 與 analysis 兩個流程是並行的且過程中會反覆交 錯影響 )

Software Engineering for Digital Home 6 Functional requirements Describe functionality or system services. ( 描述系統的功能、服務 ) How the system should react to particular inputs and how the system should behave in particular situations. ( 描述系統遇到哪些輸入要有何種反應，當系統遇到哪些 狀態會何種處理行為 ) Functional requirements do not focus on any of the implementation details. (Functional requirements 只表達需要系統提供什麼功能或服 務，而不著重於怎麼實作這些功能或服務 )

Software Engineering for Digital Home 7 Nonfunctional requirements Non-functional requirement Product requirement Implementatio n requirement Delivery requirement Organisational requirement Space requirement Performance requirement Usability requirement Portability requirement Reliability requirement Efficiency requirement Standards requirement Legislative requirement Ethical requirement Interoperability requirement External requirement Privacy requirement Safety requirement

Software Engineering for Digital Home 8 Product requirements Requirements which specify that the delivered product must behave in a particular way. e.g. 1.Yahoo 會員註冊 (Usability requirement)Yahoo 2. 需同時服務 50 個 user 上線，每個 request 的 response time 要在 2 秒之內 (Performance requirement) 3. 對於正常的連線操作狀態下，發生當機的錯誤率不可 超過千分之一 (Reliability requirement) 4.Microsoft Windows 2000 至今的 Server 系列皆須能安裝 以及執行本系統 (Portability requirement)

Software Engineering for Digital Home 9 Organisational requirements Requirements which are a consequence of organisational policies and procedures. e.g. 1. 需求規格，設計文件，實作的產品 (delivery requirement) 2. 限制使用物件導向方式設計 (implementation requirement)  符合 SCORM 2004 的標準 (standard requirement)

Software Engineering for Digital Home 10 External requirements Requirements which arise from factors which are external to the system and its development process. e.g. 1. 本系統需與公司舊有資料庫溝通，舊有資料庫機器上 所使用的處理器為 32 bit (Interoperability requirement) 2. 不能只利用 user 的姓名或是編號就可以顯示出 user 的所 有資訊 (privacy requirement)

Software Engineering for Digital Home 11

Software Engineering for Digital Home 12

Software Engineering for Digital Home 13 Requirements elicitation activities Problem statement Requirements elicitation Nonfunctional requirements Function model Specification Requirements Identifying actors and scenarios Identifying use case Refining use case and identifying relationship Identifying nonfunctional requirements Scenario Use cases Detailed use cases

Software Engineering for Digital Home 14 Problem statement After an initial meeting with the client, the problem statement is written. ( 在 project manager 跟客戶聊天喝茶後客戶要求的系統 problem statement 由 project manager 記錄下來 ) Problem

Software Engineering for Digital Home 15 教學網站 由於資訊的進步，現在有很多的教學已資訊化，老師及學生需要一個平 台來溝通，老師要提供上課教材給學生下載．有時候老師開放 ftp ， e- mail 給學生交作業等等．但這樣的方式並不是很方便． 由於老師都需要這些功能，所以我們希望建立一個教學網站的系統，借 由此系統老師及助教可以很容易對於課程教材、學生資料以及作業、報 告及成績等進行輕鬆的控管。學生可利用系統進行教材的下載，成績查 詢等功能。 老師，助教及學生也可以利用系統進行互相討論課業及互相聯絡的進階 功能。 教學網站為一個線上的系統, 使用者可透過網頁瀏覽器對教學網站進行 管理, 使用.

Software Engineering for Digital Home 教學網站 (cont.) 教學網站的基本功能為 - 課程介紹, 課程行事曆, 課程公告, 資料下載, 作業上 / 下載, 報告上 / 下載, 成績查詢, 課程通訊 錄, 討論區. 希望使用 asp /asp.net 開發. 要支援 50 人同時上線. 在正常 的連線操作下, 發生當機的錯誤率不可超過千分之一. 系統要可以安裝在 Microsoft Windows Server 2000 以上的 版本. Sql 2000 以上的資料庫. 不能只利用使用者的姓名或是編號就可以顯示 user 的所有 資訊. 16

Software Engineering for Digital Home 17 Requirements elicitation activities Problem statement Requirements elicitation Nonfunctional requirements Function model Specification Requirements Identifying actors and scenarios Identifying use case Refining use case and identifying relationship Identifying nonfunctional requirements Scenario Use cases Detailed use cases

Software Engineering for Digital Home 18 Identifying actors What is an actor? –An actor can be human or an external system that exchange information with the system. ( 只要跟本系統做資訊交換這種動作的人或是外部系統都能稱為 actor) What is the purpose? –To find all the perspectives from which the developers need to consider the system. ( 讓系統開發人員可以經由各個 actor 的角度思考系統的製作 )

Software Engineering for Digital Home 19 Identifying actors How to identify actors? –Which user groups are supported by the system to perform their work? ( 系統要為哪些使用族群服務 ) –Which user groups execute the system’s main functions? ( 系統的主要功能提供給哪些族群使用 ) –Which user groups perform secondary functions? ( 系統的次要功能提供給哪些族群使用 ) –With what external hardware or software system will the system interact? ( 有什麼外部軟體或是硬體跟本系統互相進行資料傳遞 )

Software Engineering for Digital Home 20 Identifying scenario What is a scenario? –A scenario is a concrete, focused, informal description of a single feature of the system from the viewpoint of a single actor. ( 一份 scenario 是從一個 actor 的角度描寫一項系統特徵 ) What is the purpose? –The emphasis for developers during scenario identification is to understand the application domain. ( 透過 scenario 開發人員可以了解本系統要做某個領域的什麼服務 )

Software Engineering for Digital Home 21 Identifying scenario How to identify scenario? –What are the tasks that the actor wants the system to perform? ( 系統要為這名 actor 提供什麼服務 ? ) –What information does the actor access? Who creates that data? Can it be modified or removed? By whom? ( 這名 actor 可以存取什麼資訊，這些相關的資訊又是誰建立的 ? 這些資訊可 以被修改或移除嗎 ? 如果可以，是由哪些 actor 進行這項動作 ) –Which external changes does the actor need to inform the system about? How often? When? ( 有哪些外部資訊是由 actor 告知系統的 ? 什麼狀況下會有這樣的動作 ? ) –Which events does the system need to inform the actor about? With what latency? ( 系統發生了什麼事件必須通知 actor?)

Software Engineering for Digital Home 22 教學網站 scenario Scenario name 繳交作業 Participating actor instances Alice : 老師, Bill : 學生 Flow of events Alice 是 OOSE 課程的老師, Alice 在教學網站上開一個 作業, 要求學生分析出教學網站所有的 use case. Alice 在教學網站上建立了這個作業. 及繳交日期等資 訊. Bill 在上完課後, 很認真的把作業完成了, 他登入教學 網站, 選到 OOSE 課程中, 把作業上傳到教學網站中. 在作業截止後, Alice 把所有學生繳交的作業下載下來, 一一批改, 並把成績登錄在系統上.

Software Engineering for Digital Home 23 Requirements elicitation activities Problem statement Requirements elicitation Nonfunctional requirements Function model Specification Requirements Identifying actors and scenarios Identifying use case Refining use case and identifying relationship Identifying nonfunctional requirements Scenario Use cases Detailed use cases

Software Engineering for Digital Home 24 Identifying use case Developers can then consolidate related functionality into single use cases and split unrelated functionality into several use cases. ( 一份 use case 可以由多份 scenario 當中的功能組合而成，而一份含有許多不同 功能 scenario 可以被各自寫到多份 use cases 當中 ) Writing use cases is a craft. An analyst learns to write better use cases with experience. ( 分析師要寫一份好的 use case 是要靠經驗的 ) Simple use case writing guide (P.137 [B.B., A.H.D., OOSE 2/e]) –Use cases should be named with verb phrases. (Use cases 名稱必須使用動詞，表明 actor 要做什麼事情 ) –Actors should be named with noun phrases. (Actors 命名要用名詞 ) –A use case should describe a complete user transaction. (Actor 要做與要系統做並且會發生的事件從頭到尾一件一件按照順序描述 ) –Exceptions should be described separately. ( 每個例外狀況視為一個事件寫下 ) –…

Software Engineering for Digital Home 25 High-level use cases diagram 建立作業 學生 老師 > 繳交作業 >

Software Engineering for Digital Home 26 教學網站 use case Use case name 建立作業 Participating actors Initiated by 老師 Communicates with 學生 Flow of events 1. 老師要建立作業. 2. 老師輸入作業資訊. 3. 系統檢查輸入的資訊是否正確. 4. 如果正確, 系統就建立止作業. Entry condition 老師登入了教學網站. Exit conditions 老師在教學網站上建立了一個新的作業.

Software Engineering for Digital Home 27 Requirements elicitation activities Problem statement Requirements elicitation Nonfunctional requirements Function model Specification Requirements Identifying actors and scenarios Identifying use case Refining use case and identifying relationship Identifying nonfunctional requirements Scenario Use cases Detailed use cases

Software Engineering for Digital Home 28 Refining use cases The elements that are manipulated by the system are detailed. ( 物件的操作細節 ) The low-level sequence of interactions between the actor and the system are specified. ( 更具體說明 actor 與系統間互動的細節 ) Access rights are specified. ( 存取權限的具體說明 ) Handling exceptions are specified. ( 例外處理的具體說明 ) Common functionality among use cases are factored out. ( 分解兩個以上的 use cases 具有的相同功能 )

Software Engineering for Digital Home 29 Detailed use cases diagram 建立課程 老師 學生 > 發佈公告 上傳教材 發佈成績 建立作業 > 繳交作業 查詢成績

Software Engineering for Digital Home 30 Detailed use case Use case name 建立作業 Participating actors Initiated by 老師 Communicates with 學生 Flow of events 1. 老師要建立作業. 2. 老師輸入作業的名稱 (50 字元 ), 作業的要求 (2000 字元 ), 截止日期 ( 日 期格式 ). 3. 系統檢查輸入的作業名稱, 作業的要求, 截止日期是否正確. 4. 如果正確, 系統就建立止作業. Exceptions 3.1 如果所輸入的資料不正確, 系統要求使用者重新輸入. Entry condition 老師己登入教學網站. Exit conditions 老師在教學網站上建立了一個新的作業.

Software Engineering for Digital Home 31 Requirements elicitation activities Problem statement Requirements elicitation Nonfunctional requirements Function model Specification Requirements Identifying actors and scenarios Identifying use case Refining use case and identifying relationship Identifying nonfunctional requirements Scenario Use cases Detailed use cases

Software Engineering for Digital Home 32 教學網站 nonfunctional requirements CategoryNonfunctional requirements Reliability 若 Server shut down 則必須在 40 分鐘內恢復運作 Scalability 系統必須最少可以讓 50 位使用者正常連線與執行 Implementation 只要安裝有支援 cookies, Javascript, 瀏覽器的使用者 都要可以使用教學網站 教學網站要可以在 windows server IIS +SQL Server 2000 上安裝在執行

Software Engineering for Digital Home 33 Software Requirements Specifications(SRS) 1.Introduction 1.1Purpose 1.2Scope 1.3Definitions, acronyms, and abbreviations 1.4References 1.5Overview 2.Overall description 2.1Product perspective 2.2Product functions 2.3User characteristics 2.4Constraints 2.5Assumptions and dependencies 3.Specific requirements 3.1External interface requirements 3.2Functional requirements 3.3Performance requirements 3.4Design constraints 3.5Software system attributes Appendices Index

Software Engineering for Digital Home 34 Exercise 為什麼我們通常都用 scenario 詢問客戶而不用 use case? Scenario 通常已經充分敘述了系統功能，為什麼我們還需 要 use case? 請寫出 學生繳交作業 的 Detail use case. 請劃出 學生繳交作業 的 use case diagram.