uml ch2 lect

7/24/2019 UML Ch2 Lect

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Bernd Bruegge & Allen Dutoit Object-Oriented Software Engineering: Conquering Complex and Changing Systems 16

UML First Pass: Use Case Diagrams

WatchUser WatchRepairPerson

ReadTime

SetTime

ChangeBattery

Actor

Use case

PackageSimpleWatch

Use case diagrams represent the functionality of the system

from users point of view


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UML First Pass: Class Diagrams

Battery

load()

1

2

Time

now()

PushButton

state

push()

release()

1

1

1

1

1

2

blin!d"

blinSeconds(

)

blin#inutes(

)

blin$ours()

stopBlining(

)

re%eresh()

&C''isplay

SimpleWatch

Class

AssociationMultiplicity

Attributes

Operations

Class diagrams represent the structure of the system


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UML First Pass: Sequence Diagram

Object

MessageActivation

Sequence diagrams represent the behavior as interactions

blin$ours()

blin#inutes()

increment#inutes()

re%resh()

commitewTime()

stopBlining()

pressButton1()

pressButton2()

pressButtons1nd2()

pressButton1()

*WatchUser *Time*&C''isplay

*SimpleWatch


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button1+2Pressed

button1+2Pressed

button1Pressed

button2Pressed

button2Pressed

button2Pressed

button1Pressed

button1+2Pressed !ncrement#inutes

!ncrement$ours

Blin$ours

BlinSeconds

Blin#inutes

!ncrementSeconds

StopBlining

UML First Pass: Statechart Diagrams

StateInitial state

Final state

Transition

Event


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UML Second Pass: Use Case Diagrams

Used during requirements elicitation torepresent external behavior

Actorsrepresent roles, that is, a type

of user of the system Use casesrepresent a sequence of

interaction for a type of functionality

The use case model is the set of alluse cases. It is a complete descriptionof the functionality of the system andits environment

Passenger

PurchaseTicet


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Use Case

A use case represents a class offunctionality provided by the system asan event flow.

A use case consists of: Unique name

Participating actors

Entry conditions

Flow of events Exit conditions

Special requirements

PurchaseTicet


7/15Bernd Bruegge & Allen Dutoit Object-Oriented Software Engineering: Conquering Complex and Changing Systems 25

Use Case Example

Name:Purchase ticket

Participating actor:Passenger

Entry condition:

Passengerstanding in frontof ticket distributor.

Passengerhas sufficientmoney to purchase ticket.

Exit condition:

Passengerhas ticket.

Event flow:1.Passengerselects the number

of zones to be traveled.

2. Distributor displays the amountdue.

3.Passengerinserts money, ofat least the amount due.

4. Distributor returns change.

5. Distributor issues ticket.

Anythingmissing?

Exceptional cases!



The,,e"tend-- Relationship

relationships representexceptional or seldom invoked cases.

The exceptional event flows arefactored out of the main event flowfor clarity.

Use cases representing exceptionalflows can extend more than one usecase.

The direction of a relationship is to the extended usecase

Passenger

PurchaseTicet

Time/ut

,,e"tend--

oChange

,,e"tend--/ut/%/rder

,,e"tend--

Cancel

,,e"tend--



Passenger

PurchaseSingleTicet

Purchase#ultiCard

oChange

,,e"tend--

Cancel

,,e"tend--

,,include--

Collect#oney

,,include--

The Relationship

An relationship representsbehavior that is factored outof the use case.

An representsbehavior that is factored out

for reuse, not because it is anexception.

The direction of arelationship isto the using use case (unlike

relationships).


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Classes

Aclassrepresent a concept.

A class encapsulates state (attributes)and behavior (operations). Each attribute has atype.

Each operation has asignature.

The class name is the only mandatory information.

0one2price

getones()

getPrice()

Tari%%Schedule

Table0one2pricenumerationgetones()

PricegetPrice(one)

Tari%%Schedule

Name

Attributes

Operations

Signature

Tari%%Schedule


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Aggregation

Anaggregation

is a special case of association denoting aconsists of hierarchy.

Theaggregateis the parent class, thecomponentsare thechildren class.

1

"haust System

#u%%ler Tailpipe

3442


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Composition

A solid diamond denotecomposition, a strong form ofaggregation where components cannot exist without theaggregate.

5

Ticet#achine

oneButton


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Generalization

Generalization relationships denote inheritance between classes.

The children classes inherit the attributes and operations of theparent class.

Generalization simplifies the model by eliminating redundancy.

Button

oneButtonCancelButton


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UML Sequence Diagrams

Used during requirements analysis To refine use case descriptions

to find additional objects(participating objects)

Used during system design

to refine subsystem interfaces

Classesare represented bycolumns

Messagesare represented byarrows

Activationsare represented bynarrow rectangles

Lifelinesare represented bydashed lines

selectone()

picupChange()

picUpTicet()

insertCoins()

PassengerTicet#achine


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UML Sequence Diagrams: Nested Messages

The source of an arrow indicates the activation which sent themessage

An activation is as long as all nested activations

selectone()

Passenger oneButton Tari%Schedule 'isplay

looupPrice(selection)

displayPrice(price)

price

Dataflow

to be continued...

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