Stephenson College DP 98 1

Associations & Aggregations

by Derek Peacock

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Associations

One to One One to Many Many to Many

0..1 10

Associates with

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Uni-Directional Association

Switch Light bulbControls

ActorServer

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Application Associations

Lecturer UnitsTeaches

Contract

Teaches to

*

Classroom

Taught in

*

*

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Containment v. Containers

One object composed of fixed no of other objects

Can not exist without its components

e.g. a Car is composed of and engine, four wheels

One object may contain a variable no of other objects

Can exist independently

e.g. a Car Boot may contain some luggage, some books, some wine

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Composition (of parts)

Clock

Hand Face Body

2

Battery

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Aggregation

Parts can have independent life outside aggregation

e.g. a battery as part of a clock, as opposed to the hands of the clock

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A Checkout Aggregation

Checkout

Barcodereader

Weighing scale

Till

CustomerQueue

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The Solent Hotel

Has 5 function rooms @ £200 Has 40 bedrooms 10 single bedrooms @ £40 30 double rooms @ £55 One set of presentation equipment Customers name and payee recorded

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UML Class Diagram (1)

Hotel

Single Room

DoubleRoom

FunctionRoom

Equipment

Is in0..1

10 30 5

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UML Class Diagram (2)

Single Room

DoubleRoom

FunctionRoom

Room CustomerBooks

0..1