Object-Oriented Object-Oriented Software EngineeringSoftware Engineering

More Modelling with ClassesMore Modelling with Classes

Paul J KrausePaul J Krause

More Modelling with ClassesMore Modelling with Classes

ContentsContents Overview of Associations Overview of Associations Generalisation/Specialisation hierarchiesGeneralisation/Specialisation hierarchies AggregationAggregation Why I don’t like aggregationWhy I don’t like aggregation InterfacesInterfacesSome examples taken from: Mellor and Some examples taken from: Mellor and

Balcer, Balcer, Executable UMLExecutable UML, Addison Wesley, Addison Wesley

ClassClass

Tuner class name

channelfrequency attributes

get_Frequencyset_Frequency

operations

Inheritance HierarchyInheritance Hierarchy

Tuner

A/V Tuner FM Tuner

AggregationAggregationSurf List

surfListSize

addSurfChanneldeleteSurfChannelsetSurfChannel

Source ID

presetNumberpresetName

setPresetNumbersetPresetName

0..*

AssociationAssociation

Tuner

Surf List1

1

Putting it all togetherPutting it all together

A/V Source

Front End External Source

Surf List

Source ID

0..*

11

Tuner

1..*

is tuned to

Publisher

nameaddresswebSite

BookProduct

bookNumbertitleunitPrice

Customer

nameemailshippingAdd

Author

nameaddresswebSite

R1 R3

R2

is producedand

marketedby

producesand

markets

is apurchase

of

is sold as

wrote

was written by

1 0..* 1..* 0..*

1..*

1..*

Order

quantitysalePricedate

makes 1..*

is made by 1

““Nonuniform Classes”Nonuniform Classes”

Consider an on-line “book store”. It may Consider an on-line “book store”. It may actually sell a variety of products.actually sell a variety of products.

Product

productID: ProductCodetitle: stringcopyright: YearunitPrice: Moneydescription: stringbookNumber: ISBNsubtitle: stringrecordingLength: TimeproductVersion: string

applicable to allProducts

only forBooks

only for Recordings (CDs, videos …)

only for Software

Separate Product Classes?Separate Product Classes?

BookProduct

productID: title: copyright:unitPrice:description:bookNumber:subtitle:

RecordingProduct

productID: title: copyright:unitPrice:description:recordingLength:

SoftwareProduct

productID: title: copyright:unitPrice:description:productVersion:

Partitioning ProductsPartitioning Products

All Products

Recording Products

Book ProductsBook Products

No Products remain outside a set No products are in more than one set

Generalisation - SpecialisationGeneralisation - Specialisation

BookProduct

bookNumber:subtitle:

RecordingProduct

recordingLength:

SoftwareProduct

productVersion:

Product

productID: title: copyright:unitPrice:description:

R11 {disjoint, complete}

DefinitionsDefinitions

A A superclasssuperclass is a class that is a generalisation of is a class that is a generalisation of a set of conceptsa set of concepts

A A subclasssubclass is a specialisation of a high-level is a specialisation of a high-level conceptconcept

A A leaf-subclassleaf-subclass is a subclass that is not also a is a subclass that is not also a superclass of another classsuperclass of another class

Generally, superclasses will be Generally, superclasses will be abstract classesabstract classes it is not normally possible to create instances of themit is not normally possible to create instances of them

Repeated SpecialisationRepeated SpecialisationAccount

{abstract}

CheckingAccount{abstract}

SavingsAccount

RegularCheckingAccount InterestCheckingAccount

R1 {disjoint, complete}

R2 {disjoint, complete}

Adding an AssociationAdding an Association

Publisher

groupCode:publisherCode:name:address:website:

isproducedandmarketedby

producesand

markets

1 0..*R1

BookProduct

bookNumber:subtitle:

RecordingProduct

recordingLength:

SoftwareProduct

productVersion:

Product

productID: title: copyright:unitPrice:description:

R11 {disjoint, complete}

Aggregation - “part of”Aggregation - “part of”

Vehicle

TransmissionEngine Wheels

“A Vehicle is an aggregation (made up) of an Engine, a Transmission and some Wheels (and some more stuff… )”

Complex structures?Complex structures?

PictureSoundFeaturesInstallationFeatures Timer

Parental ControlChild LockSleep

Parental Control Block AllClearTV RatingFilm RatingTV Rating TV Y

TV Y7PGTV 14 …

Menu

MenuItem

1..*

LeafItem SubMenu

1

isselected from

selects

1

CarAeroplane TruckBicycle

SportsCar

Vehicle

VehicleComponent

1..*1..*

EngineTransmissionWheel

JetEngine PistonEngine ElectricMotor

Amphibious Vehicle

Aeroplanes, Bicycles, Cars, Trucks and Amphibious Vehicles are "kinds of" Vehicle

A Sports Car is a "kind of" Car

A Vehicle is an "aggregation" of VehicleComponents

Wheel, Transmission and Engine are "kinds of" VehicleComponents

JetEngine, PistonEngine and ElectricMotor are "kinds of" Engine

NOTE: In this model I may want to add in some additional constraints on what kinds of VehicleComponents are associated with specific kinds of Vehicle

Avoiding AggregationAvoiding Aggregation

Vehicle

Engine

powers

ispoweredby

1

1..*

Transmission

Wheel

transmitspower

through

isdriven by

11 0,1

1..* generatesmotionvia

isrotatedby

issupportedby1..*

1

supports

Aggregation - Who needs it?Aggregation - Who needs it?

Menu

MenuItem

1..*

LeafItem SubMenu

1

isselected from

selects

1

1

consists of

is contained in

InterfacesInterfaces

Sometimes we may find two or more Sometimes we may find two or more different subclasses share some common different subclasses share some common behaviourbehaviour

In this case, they are not strictly “kinds of” In this case, they are not strictly “kinds of” some common parentsome common parent

Rather, they “behave like” some common Rather, they “behave like” some common pattern (under certain circumstances)pattern (under certain circumstances)

We say that they both implement a We say that they both implement a common interfacecommon interface

A “Cashier” InterfaceA “Cashier” Interface

Person Machine

ATMEmployee

«interface»Cashier

withdrawdeposit