Sequence Diagram PBL

8/8/2019 Sequence Diagram PBL

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ObjectInteraction

Sequence DiagramsWeek 7


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Objectives:

To model objectcollaboration using an interaction

sequence diagrams

Identifyand transform the usecasespecification

into sequence diagrams using UML notation.


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Interaction Diagram Interaction diagram is used to describe the

object interaction.

It is used to determine the most appropriatescheme of messaging between objects in order

to support a particular user requirements.

2 types of interaction diagram:

- sequence diagram

- collaboration diagram


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Sequence Diagrams Thesequence diagram showstheinteractions

among objectsthatparticipatein a usecaseand

the messagethatpassbetween them overtimefor one usecase.

Itisa dynamic modelthatshown in atimesequence.

Typically used to representthe detailedinteraction among object oftheclasses, notamong theclassesthemselves.


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Sequence Diagrams. Each usecasehasa number offlows

(basicflow,exceptionalflowsand

alternativeflows)

Eachsequence diagram represents ofthe

flowsthrough usecase diagram.


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Elements ofSequence Diagrams Actor

- Aperson/system thatparticipatesin a

sequencebysending or receiving

message.

- placeacrossthetop ofthe diagram using

actorsymbol (refer use-case diagram)

Actor


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- Placeacrossthetop ofthe diagram

using objectsymbol. Participatesin asequencebysending or receivingmessage.

Elements ofSequence Diagrams

Object

Object


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- Objectscommunicatebysending

messages- Messageisan information sentto objects

to execute one ofitsbehaviour.

- using solid linesconnecting two objects.


Message

CustomerPanel DrinkMgrSelect drink


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lifeline

- using dotted line runsverticallybeloweachactorand objectto denotethelifeline oftheactor/objectovertime.

I

I

II

I


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Focus of control

- isalong, narrow rectangleplaced atopa

lifeline.- indicatestimes during an activation when

processing istaking placewithin the object.


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Reflexive message

- objectcan send messageto itself


Object

m e s s age


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Example ofSequence diagram

The process begins when Joe inserts his card into thecard reader. The card reader reads the number on Joescard, then tells the ATM screen to initialize itself. TheATM prompts Joe forhis PIN. Joe enters his PIN andthe ATM opens his account. Joes PIN is validated, andthe ATM prompts him for a transaction. Joe selects

Withdraw. The ATM prompts Joe for the withdrawalamount. Joe enters $20. The ATM verifies that Joesaccount has sufficient funds, and subtracts $20 fromthe account. The ATM dispenses $20 and ejects Joescard.

Scenario : Joe, a bank customer withdrawing $20from the ATM


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Example ofSequence diagram

Focusof control

Reflexivemessage

object

Lifeline

Complete Sequence diagram

Joe AccountJoe :

ustomer ard Reader ATM creen

ash dispenser ATM Manager

insert cardread card no.

prompt PIN

enter PIN

send card no.

initialize screen

send PIN retrieve PIN

validate PIN


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Stepsforbuilding Sequence

Diagram Setthecontext ofsequence diagram

- definewhich usecase/ ascenario ofa use

case (normalflow,alternativeflowandexceptionalflow)

Identifywhichactorwillinvolve

Identifywhich objectswillparticipate

Setthelifelineforeach object Layoutthe messagefrom thetopto the

bottom ofthe diagram based on the orderinwhichtheyarearesent.


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Stepsforbuilding Sequence

Diagram.

Add thefocus ofcontrolto each objects

life Validatethesequence diagram


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ExerciseIts time

to do the

exercise


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Based on the usecasespecification given,drawasequence diagram forbasicflow of

Buy Drink

Use Case Specification


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Documents

Sequence Diagram PBL