Sequence diagrams

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Sequence diagrams
Object-Oriented Design Module 4
John Leaney, Lian Loke, Lizveth Robles University
of Technology, Sydney
Contributors
John Reekie, University of Technology, Sydney
Terms of Use Creative Commons Attribution-ShareAl
ike 2.5 http//creativecommons.org/licenses/by-sa/
2.5/
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Overview

• Last OO design session, we represented the static
  structure of the model for a system in a UML
  Class Diagram
• Classes, generalization, association
• This week we will look at UML Interaction
  Diagrams
• Sequence diagram
• Quick-and-dirty version
• Collaboration diagram
• Referenceshttp//www.softwarepractice.org/coursew
  are/index.php/design/sequence_diagrams

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Diagrams in UML
Use case Diagram
Development Diagram
Statechart Diagram
Views
Activity Diagram
Component Diagram
Object Diagram
Sequence Diagram
Collaboration Diagram
Class Diagram
Knoernschild, p. 55
UML has a lot of different diagrams! Use them as
appropriate.
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Interaction Diagrams

• UML notation for illustrating
• how objects interact via messages
• the sequence of events and interactions between a
  set of objects
• A single diagram is typically drawn for a
  particular scenario or use case.
• Can be used at different stages in system
  development.
• We will focus on the use of interaction diagrams
  at the design stage.

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Common Notation

• Classes and Instances

Client
Client
c1Client
instance
named instance

• Message notation

return value message(parameter
parameterType) returnType
s calculateSalary(hours) s calculateSalary
(hours Integer) Double
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An example sequence interaction diagram
Scenario Check campaign budget
Note The blackened segments show when the object
has the focus of control. You do not normally
show this on your diagrams.
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Sequence Diagram

• Shows the sequence of events that occur in a
  scenario
• Shows the detailed interaction between objects
• Good for presenting sequence or time ordering of
  messages
• Constrained format in which more objects are
  added to the diagram horizontally to the right
• i.e., can run out of room on the paper

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Sequence Diagram Notation

• Messages
• Focus of control and activation boxes
• Illustrating Returns
• Messages to self or this
• Creation of instances
• Object Lifelines and Object Destruction
• Iteration or looping
• Conditional messages

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Notation Samples 1
synchronous message synchronised with source
by a return messagein context of overall normal
message flow
anonymous objectnot named
Client
getName ( )
Activation boxWhen this message trace is active
return message
object lifeline
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Notation Samples 2
instance creation message
Campaign
named object
addNewAdvert( )
synchronous message
create( ) ltltcreategtgt
adv1 Advert
autoDestroy()
message to self
object destruction
X
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Notation Samples 3
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Notation Samples 4
A
B
C
calculate (x )
xgt10calculate( )
xlt10 calculate( )
Mutual exclusive conditional messages
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Synchronous and Asynchronous messages
Time constraints are mainly used in real-time
systems
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Example - Sequence Diagram 2
Scenario Add a new advert to a campaign with
boundary and control classes
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Quick-and-dirty

• Sometimes we want to quickly sketch the essence
  of the interaction without bothering about
  correct syntax
• Here we present a no-frills way of drawing
  sequence diagrams, called Quick-and-dirty
• Suited to drawing by hand
• Of course, when formally documenting your design,
  you should use formal UML syntax
• ? Use Quick-and-dirty sequence diagrams in your
  project workbook to explore and present your
  design

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Sample 1 Quick-and-dirty
named instance
anonymous instance
player
hand
Card
valueHand
getValue
totalValue
synchronous message
addCard(aCard)
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Sample 2 Quick-and-dirty
addAdvert
addAdvertUI
CampaignManager
startInterface
selectClient
asynchronous message
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Collaboration Diagram

• Shows the messages sent between objects without
  the linear order shown in a sequence diagram.
• Concentrates on the collaborations between
  objects.
• Better than sequence diagrams for illustrating
  complex branching, iteration, and concurrent
  behaviour.

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Example - Collaboration Diagram 1
Scenario Register payment of a sale
direction of message
first internal message
1 makePayment(cashTendered)
makePayment(cashTendered)
Register
Sale
link line
1.1 create(cashTendered)
first message
parameter
Payment
creation indicated with a
instance
"create" message
Ref Larman
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Collaboration Diagram Notation

• Links
• Messages
• Messages to self or this
• Creation of instances
• Message Number Sequencing
• Conditional messages
• Iteration or looping

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Example - Collaboration Diagram 2
Scenario Add a new advert to a campaign
Client is responsible for providing data about
campaigns to AddAdvert
Bennett, Figure 9.13
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Example - Collaboration Diagram 3
Can show different possible allocations of
responsibility
Scenario Add a new advert to a campaign
Here Client is responsible for providing
AddAdvert with a list of its campaigns. AddAdvert
is now responsible for getting campaign details
directly from Campaign objects.
Bennett, Figure 9.14