This document provides an overview of sequence diagrams and their use in UML modeling. It discusses the importance of sequence diagrams in depicting object interactions for use cases. The document outlines basic rules for constructing sequence diagrams, including identifying initiating events, messages, and synchronous/asynchronous calls. It provides examples of system sequence diagrams for various use cases of a vending machine system. These diagrams show object interactions and information flow over time to achieve the desired behaviors.

1. UML Diagrams:
Sequence Diagrams

2. Outline
• The Requirements Model and the Analysis model
• Importance of Sequence Diagrams
• Rules of sequence diagrams
• Use Cases and Sequence Diagrams
• The System Sequence Diagrams
• The Vending Machine Example
• Other Examples

3. The Requirements Model and the
Analysis Model
Static Analysis
Dynamic Analysis
Functional/
Nonfunctional
Requirements
Use Case Diagrams/
Sequence Diagrams
(the system level)
- Class Diagrams
- State Diagrams/
Refined Sequence
Diagrams (The object
level)
The Requirements
Elicitation
Process
The Object-Oriented
Analysis
Process

4. Importance of Sequence Diagrams
• Depict object interactions in a given
scenario identified for a given Use Case
• Specify the messages passed between
objects using horizontal arrows including
messages to/from external actors
• Time increases from Top to bottom

5. Rules of Sequence Diagrams
• Sequence Initiation
updateStatus( )
Click Update Button
User
Object1:C1 Object2:C2

6. Rules of Sequence Diagrams
• Identify objects needed to support use case,
determine sequence of internal events following
the external initiating event
• Diagrams that are not initiated with an external
actor represent only a partial sequence
• Partial sequence diagrams should clearly identify
the actor initiated sequence diagrams from which
they are launched

7. Rules of Sequence Diagrams
• Messages specified on interactions can be
synchronous or asynchronous
updateStatus( )
Object1:C1 Object2:C2
calcRoute( )
route
Object1:C1 Object2:C2
Implicit Returns Explicit Return
Object3:C3
generateMessage( )
Synchronous call

8. Rules of Sequence Diagrams
Asynchronous call
asynchronous_Call ()
callBack ()
Object1:C1
{active}
Object2:C2
{active}

9. Rules of Sequence Diagrams
• Display operation names on call arrows
c:client
factory:
cmd_pktCToCHeaderFactory
header:
cmd_pktCToCCommandHeader
buildHeader( char * )
«create»
header

10. Rules of Sequence Diagrams
Compound and Simple Iteration
* [for all
Interfaces in
Container] Find( )
amMasterSI( )
setState( )
getInterfaceContainer()
* [for all Interfaces in Container] publishState() setOn( ) / setOff( )
{
:DiscreteFD
:DiscreteFD
:Interface
:Interface:InterfaceContainer:Subsystem :Resource

11. ‘included’ sequence diagrams
Command Response
Command Request
Command Request
Command Response
<<includes>>
Process Command
Response sequence
<<includes>>
Process Command
Request sequence
Application Process
with CIF
CMM:process target:process

12. Showing alternate behavior in a sequence
diagram
validateCommand( )
issueCommand( )
User Application
[if valid command] routeCommand( )
[if invalid command] logError( )
display(status)
:CmdHandler :CmdValidater :CmdRouter :EventLog :StatusDialog

13. Showing Extension Point
validateCommand( )
routeCommand( )
display( status)
Extension Point
[invalid command]
abort command
request and send
system message
:StatusDialog:CmdRouter:CmdValidater:CmdHandler
issueCommand( )
User Application

14. Specifying Timing Requirements
a: Command
Create Transaction
b: Command
d: Response
Remove Transaction
c: Response
CMM : process target : process
User Application
{b.receiveTime ≤
a.sendTime + 50ms}
{d.receiveTime ≤
a.sendTime + 1s}

15. System Sequence Diagram
for Deposit Money Use Case
C u s t o m e r
M o n e y D e t e c t i o n
H a r d w a r e
C R T D i s p l a y
V e n d i n g M a c h i n e
C o n t r o l l e r
D e p o s i t M o n e y
[ I d l e S t a t e ]
D i s p l a y W e lc o m e
M e s s a g e
D i s p l a y A m o u n t
S e n d A m o u n t
P r o m p t f o r S e l e c t i o n
S t a r t T i m e r
[ I f T i m e r > 3 0 s e c o n d s a n d I n v a l i d o r N o S e l e c t i o n ]
R e t u r n M o n e y
M o n e y
D i s p e n s e r
S t o p
T i m e r[ I d l e S t a t e ]
D i s p l a y W e l c o m e
M e s s a g e

16. System Sequence Diagram
for Make Selection Use Case
C u s t o m e r
N u m e r ic K e y p a d C R T D is p la y
V e n d in g M a c h in e
C o n t r o lle r
M o n e y
D is p e n s e r
P r o d u c t
D is p e n s e r
P r o m p t
f o r
S e le c t io n
E n t e r S e le c t io n
D is p la y S e le c t io n
S e n d S e le c t io n
P r o d u c t
D a t a b a s e
I n q u ir e D a t a b a s e
[ if I n v a lid S e le c t io n ]
P r o m p t f o r A n o t h e r S e le c t io n
D is p e n s e P r o d u c t
D is p e n s e C a lc u la t e d
C h a n g e[ I d le S t a t e ]
D i s p la y W e lc o m e
M e s s a g e
N o t e : I n s u f f i c i e n t
m o n e y , s e l e c t i o n
n o t a v a i l a b l e
N o t e : I f
R e l e a s e - I n p u t
B u t t o n P r e s s e d s e e
C a n c e l l a t i o n
S e q u e n c e D i a g r a m
R e t u r n R e s p o n s e
V a lid a t e
U p d a t e D a t a b a s e

17. System Sequence Diagram
for Cancellation Use Case
C u s t o m e r
N u m e r ic K e y p a d C R T D is p la y
V e n d in g M a c h in e
C o n t r o lle r
M o n e y D is p e n s e r
P r o m p t
f o r
S e le c t io nR e le a s e - I n p u t
B u t t o n P r e s s e d
S e n d C a n c e lla t io n S ig n a l
[ I d le S t a t e ]
D is p la y W e lc o m e
M e s s a g e
R e t u r n M o n e y

18. System Sequence Diagram
for Update Database Use Case
M a i n t e n a n c e
O p e r a t o r
A ll H a r d w a r e
E x c e p t C R T D i s p la y
C R T D i s p la y
V e n d i n g M a c h i n e
C o n t r o l l e r
P r o d u c t
D a t a b a s e
W ir e le s s K e y b o a r d
P o w e r O n
S e n d A c t i v e S i g n a l
D is p la y P r o g r a m m in g
I n f o r m a t i o n
D is a b le
E n a b l e
S e n d U p d a t e C o m m a n d s
U p d a t e D a t a b a s e
P o w e r O f f
[ I d l e S t a t e ]
D is p l a y W e l c o m e I n f o r m a t i o n
D is p la y U p d a t e
C o m m a n d s
T e r m i n a t e U p d a t e M o d e

19. Other Examples of Sequence Diagrams

20. A Simple Example of Using UML2
• EXAMPLE: SATELLITE CONTROL
SYSTEM

21. A Simple Example Using UML2
• SATELLITE CONTROL SYSTEM
Architectural behavior