OOD实例阅读笔记(二)
Use case 图包括的内容
Use case图是用于需求分析的工具。他和实现技术没有任何关联。他的目的写出特定情况下的需求。
首先就是要有一定的场景。场景包括特定的环境（case 发生的条件），参与的人（action）和系统所做的响应。
一般情况下回采用黑箱的use
case（blak – box
use case）。黑箱的use case不关心具体的实现。只是确定系统的责任。
下面就提供一个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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这个例子是http://alistair.cockburn.us/usecases/usecases.html
中的template的一个很整是的例子。
下面我在举一个修改密码的case.
Change Password
该case在用户选这修改密码是触发。Check输入的两个密码是否相同。Check当前用户然后更新数据库。
Purpose
允许用户修改自己的密码。
Overview
这个case是为了给用户提供修改密码的可能。用户可以通过点击“Change My Pasword”菜单项来触发。系统会弹出一个对话框供用户输入他的新密码。用户可以按“OK”或“Cancel”来选择保存或放弃修改。系统这时会检验用户输入的信息是否正确。如果用户输入正确，保存用户信息，返回主窗体。否则给用户重来的机会。
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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用户点击”Chang My Password”菜单项。
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2
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系统显示一个可以让用户输入新密码和Comfirm的对话框。
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3
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用户输入信息并点击”OK”按钮.
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4
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系统Check输入的信息。
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5
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把用户输入的信息更新到数据库。
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6
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关闭对话框。显示修改成功或失败的提示信息。结束当前case.
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Alternative courses
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3
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用户不点”OK”而点击”Cancel”。关闭对话框，结束该case.
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4
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系统监测到下列三种情况的一个：（1）旧的密码不正确。（2）两次输入的新密码不相同。（3）新密码格式不正确。系统显示一个错误信息。清除当前对话框中的内容。允许用户重试。返回到第3步。
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5
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系统保存出错。显示错误信息。结束当前case.
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