OOD實例閱讀筆記(二)
Use case 圖包括的內容
Use case圖是用于需求分析的工具。他和實現技術沒有任何關聯。他的目的寫出特定情況下的需求。
首先就是要有一定的場景。場景包括特定的環境（case 發生的條件），參與的人（action）和系統所做的響應。
一般情況下回采用黑箱的use
case（blak – box
use case）。黑箱的use case不關心具體的實現。只是確定系統的責任。
下面就提供一個use
case的描述。
USE
CASE 5
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Buy Goods
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Goal
in Context
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Buyer issues request directly to our
company, expects goods shipped and to be billed.
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Scope
& Level
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Company, Summary
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Preconditions
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We know Buyer, their address, etc.
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Success
End Condition
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Buyer has goods, we have money for the
goods.
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Failed
End Condition
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We have not sent the goods, Buyer has not
spent the money.
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Primary,
Secondary
Actors
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Buyer, any agent (or computer) acting for
the customer.
Credit card company, bank, shipping
service
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Trigger
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purchase request comes in.
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DESCRIPTION
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Step
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Action
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1
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Buyer calls in with a purchase request
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2
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Company captures buyer’s name, address,
requested goods, etc.
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3
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Company gives buyer information on goods,
prices, delivery dates, etc.
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4
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Buyer signs for order.
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5
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Company creates order, ships order to
buyer.
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6
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Company ships invoice to buyer.
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7
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Buyers pays invoice.
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EXTENSIONS
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Step
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Branching
Action
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3a
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Company is out of one of the ordered
items:
3a1.
Renegotiate order.
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4a
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Buyer pays directly with credit card:
4a1.
Take payment by credit card (use case 44)
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7a
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Buyer returns goods:
7a.
Handle returned goods (use case 105)
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SUB-VARIATIONS
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Branching
Action
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1
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Buyer may use
phone
in,
fax
in,
use
web order form,
electronic
interchange
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7
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Buyer may pay by
cash
or money order
check
credit
card
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RELATED
INFORMATION
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5. Buy Goods
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Priority:
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top
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Performance
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5 minutes for order, 45 days until paid
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Frequency
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200/day
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Channel
to actors
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not yet determined
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OPEN
ISSUES
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What if we have part of the order?
What is credit card is stolen?
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Due
Date
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release 1.0
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...any
other
management
information...
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Superordinates
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Manage customer relationship (use case 2)
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Subordinates
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Create order (use case 15)
Take payment by credit card (use case 44)
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這個例子是http://alistair.cockburn.us/usecases/usecases.html
中的template的一個很整是的例子。
下面我在舉一個修改密碼的case.
Change Password
該case在用戶選這修改密碼是觸發。Check輸入的兩個密碼是否相同。Check當前用戶然后更新數據庫。
Purpose
允許用戶修改自己的密碼。
Overview
這個case是為了給用戶提供修改密碼的可能。用戶可以通過點擊“Change My Pasword”菜單項來觸發。系統會彈出一個對話框供用戶輸入他的新密碼。用戶可以按“OK”或“Cancel”來選擇保存或放棄修改。系統這時會檢驗用戶輸入的信息是否正確。如果用戶輸入正確，保存用戶信息，返回主窗體。否則給用戶重來的機會。
Typical Course of Events
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Line
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Actor Action
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System Response
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1
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用戶點擊”Chang My Password”菜單項。
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2
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系統顯示一個可以讓用戶輸入新密碼和Comfirm的對話框。
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3
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用戶輸入信息并點擊”OK”按鈕.
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4
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系統Check輸入的信息。
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5
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把用戶輸入的信息更新到數據庫。
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6
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關閉對話框。顯示修改成功或失敗的提示信息。結束當前case.
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Alternative courses
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3
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用戶不點”OK”而點擊”Cancel”。關閉對話框，結束該case.
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4
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系統監測到下列三種情況的一個：（1）舊的密碼不正確。（2）兩次輸入的新密碼不相同。（3）新密碼格式不正確。系統顯示一個錯誤信息。清除當前對話框中的內容。允許用戶重試。返回到第3步。
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5
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系統保存出錯。顯示錯誤信息。結束當前case.
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