Use Case Diagram
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Transcript Use Case Diagram
Use Case Diagrams
Use Case
Use case
A view to system seen from outside(user)
User’s requirements on system
A set of scenario for an actor to achieve useful
works
Withdraw
Transfer
Balance
check
Bank client
deposit
Bank system
Basic Concepts
Actor
User Case
Each describes a possible interaction between an actor and the system
Use cases are actions that a user takes on a system
System
An external person, process or thing interacting with a system or class
The entity that we are going to build
Can have subsystems in it
Relationship
Connection between actors and use cases or use cases and use cases.
Actors
A user of the system
a person or another system
Identify the actors in terms of their roles
Use Case
actions users take on system
can be very high level or so fine-grained
Use “verb” or “verb+noun” style naming
borrow
return
System
module that performs the function
System or the sybsystem is shown as a rectangle
enclosing the use cases, with the system name in the
rectangle
Library System
Relationship (Use Case Diagram)
There are four kinds of relationships
Association
Extend
Include
generalization
Association Relationship
Shown by a line connecting actors to use cases
Include Relationship
Between a use case and another use case
use case A includes the function of use case B
(has-a relationship)
A
<<include>>
B
Extend Relationship
Use case can be extended by another use case
At the extension point, use case is extended
Extension point
Shows the exact extension point between the two use cases
Shows the actual logic necessary for one use case to extend another
Example : Extend Relationship
Generalization Relationship
Indicate an inheritance of an item in UML
Can be applied to actors as well as use cases
Example
Activity Diagram
What is Activity Diagram
•
Shows overall flow of control (just like
flowchart)
•
A simplified look at what happens during a
process
•
Business and operational step-by-step
workflows of components in a system
Activity Diagram Notations
Decision
Wake Up
Activity1
[hungry]
Wake Up
[Not hungry]
[hungry]
Activity2
Eat Breakfast
Go Back to Sleep
Eat Breakfast
Transition from
one activity to another
[Not hungry]
Go Back to Sleep
Two ways of showing a decision
Concurrent Path , Signal
Synchronization bar
Television
Remote.keyln(channel)
Work Out
Show New Channel
Change(channel)
Shower
Press Channel
Number
Change (channel)
Relax
Watch
Concurrent Path
Signal : when received, the signal
causes an activity to take place
(send : convex , receive : concave )
Swimlanes
• show who has responsibility for each activity. (role)
1. A salesperson calls the client and sets up an appointment
2. Onsite appointment(In the consulting firm’s office)
- corporate technicians prepare a conference room for a
presentation
3. Offsite appointment(at the client’s office)
- a consultant prepares a presentation on a laptop
4. The consultant and the salesperson meet with the client at
the agreed-upon location and time
5. the salesperson follows up with a letter
6. If the meeting has resulted in a statement of a problem, the
benefit – the activities of each role are clarified
9
Activity Diagram Example
Call client and
set up appointment
[appointment onsite]
[appointment offsite]
Prepare a conference
room
Prepare a
laptop
Meet with the client
Send followup
letter
See the
Activity Diagram
for Creating a
Document
[no statement problem]
[statement of problem]
Create proposal
Send proposal to client
1
Swimlane : shows “who” for each activity
Sales Person
Consultant
Corporate Technician
Call client and
set up appointment
[appointment onsite]
[appointment offsite]
Prepare a
laptop
Prepare a conference
room
Meet with the client
Send followup
letter
[statement of problem]
Create proposal
[no statement problem]
Send proposal to client
See the
Activity Diagram
for Creating a
Document
Example
Sequence Diagram
Purpose of Sequence Diagram
shows the sequence of messages for a particular task from a
use case diagram
Understand how use case(scenario) can be refined with detailed
information
Sequence Diagram
Time, object, and message
Lifeline and activation
Notation
:Name
Basics
Focus on order in which messages occur
time
objects
:Name1 object
message
activation
lifeline
:Name2
Messages
The first message starts at the top, typically located
on the left side
Subsequent messages are then added to the diagram
slightly lower then the previous message
: synchronous call operation : method on the arrow
: asynchronous signal
: return message (optional) : return value on the arrow
Messages can be sent to itself
Sequence diagram example
Object
Time constraint
Message
Activation
Comment
Example
Sequence for “withdraw-money” use case