UML Diagrams:

Sequence Diagrams

The Requirements Model, and

The Dynamic Analysis Model

Prof. Hany H. Ammar, CSEE, WVU, and

Dept. of Computer Science, Faculty of Computers and Information, Cairo University

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

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

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

Rules of Sequence Diagrams

• Sequence Initiation

updateStatus( )

Click Update Button

User

Object1:C1 Object2:C2

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

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

Rules of Sequence Diagrams

Asynchronous call

asynchronous_Call ()

callBack ()

Object1:C1

{active}

Object2:C2

{active}

Rules of Sequence Diagrams

• Display operation names on call arrows

c:clientfactory:

cmd_pktCToCHeaderFactory

header:

cmd_pktCToCCommandHeaderbuildHeader( char * )

«create»

header

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

‘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

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

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

Specifying Timing Requirements

a: Command

Create Transaction

b: Command

d: ResponseRemove Transaction

c: Response

CMM : process target : process

User Application

{b.receiveTime

a.sendTime + 50ms}

{d.receiveTime

a.sendTime + 1s}

Requirements Elicitation Process

Step 4. Refining Use Cases using

System Sequence Diagrams

• System sequence diagrams establish the dynamic behavior in terms of key scenarios of the system for each use case

• The system sequence diagram models a scenario of the system interactions with the environment for a given use case

• Input/output events are clearly identified in each sequence diagram,

• The State of the system before and after each event are also depicted

• Different diagrams model scenarios with the normal flow of events and the abnormal flow of events

Sequence Diagrams and Use Cases

System Sequence Diagram

The sequence diagram of use case UC1 for system S

Actor1Actor2

System: S

S1

S2

S3

S4

E11

List of Guide Words

List of Guide Words

List of Guide Words

List of Guide Words

List of Guide Words

E21

E12

E22

E32E41

E31

List of Guide Words

List of Guide Words

The use case diagram

Of system S

Example: Use Case Diagram of the

Vending Machine

Customer

Deposit Money

Make Selection

Maintenance

Operator

Update Database

Cancellation

Requirements Elicitation Process

Step 6. Identify Initial Analysis

Objects- The Initial Object-Model

Vending Machine

Controller

Numeric Keypad

Wireless

Keyboard

CRT Display

Money Detection

Hardware

Money Dispenser

Product

Dispenser

Product Database

Designate the Actor objects with the <<actor>> stereotype

above the object label

<<actor>>

<<actor>>

<<actor>>

<<actor>>

<<actor>>

<<actor>>

System Sequence Diagram

for Deposit Money Use Case

Customer

Money Detection

HardwareCRT Display

Vending Machine

Controller

Deposit Money

[Idle State]

Display Welcome

Message

Display Amount

Send Amount

Prompt for Selection

Start Timer

[If Timer > 30 seconds and Invalid or No Selection]

Return Money

Money

Dispenser

Stop

Timer[Idle State]

Display Welcome

Message

System Sequence Diagram

for Make Selection Use Case

Customer

Numeric Keypad CRT DisplayVending Machine

Controller

Money

Dispenser

Product

Dispenser

Prompt

for

Selection

Enter Selection

Display Selection

Send Selection

Product

Database

Inquire Database

[if Invalid Selection]

Prompt for Another Selection

Dispense Product

Dispense Calculated

Change[Idle State]

Display Welcome

Message

Note: Insufficient

money, selection

not available

Note: If

Release-Input

Button Pressed see

Cancellation

Sequence Diagram

Return Response

Validate

Update Database

System Sequence Diagram

for Cancellation Use Case

Customer

Numeric Keypad CRT DisplayVending Machine

ControllerMoney Dispenser

Prompt

for

SelectionRelease-Input

Button Pressed

Send Cancellation Signal

[Idle State]

Display Welcome

Message

Return Money

System Sequence Diagram

for Update Database Use Case

Maintenance

Operator

All Hardware

Except CRT DisplayCRT Display

Vending Machine

Controller

Product

DatabaseWireless Keyboard

Power On

Send Active Signal

Display Programming

Information

Disable

Enable

Send Update Commands

Update Database

Power Off

[Idle State]

Display Welcome Information

Display Update

Commands

Terminate Update Mode

Other Examples of Sequence Diagrams

A Simple Example of Using UML2

• EXAMPLE: SATELLITE CONTROL

SYSTEM

A Simple Example Using UML2

• SATELLITE CONTROL SYSTEM

Architectural behavior