---
tags: 軟體工程
title: 第八週
---
- story
- 需求、功能
- criteria
- 提出的條件
- **use case**
> an activity that the system performs, usually in response to a request by a user
- Use cases define functional requirements
- 其實就是功能
- Analysts decompose(切成) the system into a set of use cases (functional decomposition(切割)
- 把大系統切成子系統
- 把大的程式切成好幾個function
- Two techniques for Identifying use cases
- User goal technique
- Event decomposition technique
- Name each use case using Verb-Noun
---
## User Goal Technique
<center>以RMO CSMS為例</center>

- 依服務、功能來區分類別
- 使用動詞加名詞來敘述功能
---
## Event Decomposition Technique
- More Comprehensive(完整) and Complete Technique
- Identify the events that occur to which the system must respond.
- For each event, name a use case (verb-noun) that describes what the system does when the event occurs
- Event
> something that occurs at a specific time and place, can be described(描述), and should be remembered by the system
---
<center>雲狀圖</center>

- 雲內指系統內，雲外指系統外
- 人表示 extrernal event
- 鬧鐘表示 temporal event
- External Event
- an event that occurs outside the system, usually initiated by an external agent or actor
- 發生在系統外，常被外部事件觸發
- Temporal Event
- an event that occurs as a result of reaching a point in time
- 跟時間有關的event
- 時間到了，某個件事情會發生
- State Event
- an event that occurs when something happens inside the system that triggers(觸發) some process
- reorder point(訂貨點) is reached(到達) for inventory(庫存) item
- 當系統某個狀態發生時的event
- <font color = red>**每一種event就是一個use case**</font>
---
## External Event Checklist
- External agent or actor wants something resulting in a transaction
- Customer buys a product
- External agent or actor wants some information
- Customer wants to know product details
- External data changed and needs to be updated
- Customer has new address and phone
- Management wants some information
- Sales manager wants update on production plans
---
## Temporal Event Checklist
- Internal outputs needed at points in time
- Management reports (summary or exception)
- Operational reports (detailed transactions)
- Internal statements and documents (including payroll)
- External outputs needed at points of time
- Statements, status reports, bills, reminders
---
- Finding the actual event that affects the system
- 找到的event要把非系統的event刪除
- Tracing a sequence of transactions resulting in many events
- Don’t worry about functions built into system because of limits in technology and people. Wait until design
- 假設所有跟人或技術的問題都不存在
---
- 分析目的
- 搞清楚人家要什麼
- 需求
- 包含功能需求、非功能需求
- 不去管用什麼技術去實現
- what
- 設計目的
- 解決分析出來需求
- 要使用的技術
- 藍圖
- how