jonas.kvarnstrom@liu.se – 2015

Unified Modeling Language

A Brief Introduction

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2History In the early 1990s, three common OO modeling approaches James Rumbaugh's

Object-modeling technique (OMT)

Grady Booch's Booch method

Ivar Jacobson’sObject-Oriented Software Engineering(OOSE)

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3History (2) 1995: All three employed at Rational Software Known as The Three Amigos

1996: Too many modeling languages slower adoption of OO Wanted a non-proprietary language using the best parts Formed an international consortium

Result: Unified Modeling Language, UML Not a development method, just a language

Used to build a system model Part of this model can be represented

as various forms of diagrams

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4UML Diagram Types We will focus on class diagrams!

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5Usage Guidelines Why use class diagrams?

To design software before coding▪ Create a broad structure, check that it is consistent and reasonable

To help you understand existing code▪ Create a structural overview▪ Can be faster to construct and to understand a diagram

than a long text describing the same thing

How should they be used? Less is more

▪ Focus!▪ Illustrate one coherent subsystem at a time▪ Include only as much as you need

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6Simple Class Diagram General structure of a class:

ArrayList

elements: Object[]length: int

size() : intget(int amount): Objectadd(Object element): Objectset(int index, Object element): void

Class Name

Attributes

Operations (methods)

Static members: Underlined!Colors are not part of the standard –

added here for clarity!

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7Visibility Markers Visibility markers before names + Public # Protected – Private ~ Package / Derived (computed from other attributes) Also, static methods or fields are underlined

ArrayList

–elements: Object[]–length: int

+size() : int+get(int amount): Object+add(Object element): Object+set(int index, Object element): void

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8Interfaces General structure of an interface: Interface name in italics Marked with the <<interface>> ”stereotype”

List <<interface>>

+size(): int+get(int amount): Object+add(Object element): Object+set(int index, Object element): void

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9Realization Class Relationships: Realization An interface is simply a description Classes realize the interface:

Provide a concrete implementation Dashed arrow, unfilled arrowhead Members shown:

▪ Where they are declared for the first time▪ Where they are implemented / overridden

List <<interface>>

+size(): int+get(int amount): Object+add(Object element): Object+set(int index, Object element): void

ArrayList

–elements: Object[]–length: int

+size() : int+get(int amount): Object+add(Object element): Object+set(int index,Object element): void

LinkedList

–head: Object–tail: LinkedList

+size() : int…

SkipList

…

+size() : int…

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10Generalization Class Relationship: Generalization (inheritance) List specializes Collection (adds new requirements, new methods) Collection generalizes List Ordinary line, unfilled arrowhead

List <<interface>>

+get(int index): Object+set(int index, Object element): void

Collection <<interface>>

+size(): int+add(Object element): Object+contains(Object element): boolean

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11Generalization 2 Class Relationship: Generalization (inheritance) GraphicCircle specializes Circle Circle generalizes GraphicCircle Ordinary line, unfilled arrowhead

GraphicCircle

+outline, fill: Color

+draw(DrawWindow): void

Circle

+x, y, r: double

+getArea(): double

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12Composition Instance Relationship: Composition A hand is part of a person If we "remove" the person, its hands also removed Line with filled diamond

May add multiplicity▪ Every person has two hands, every hand is part of one person

Person Hand

Person Hand1 2

Omit fields/methodswhen they are not relevant!

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13Aggregation Instance Relationship: Aggregation

Alternative 1: In our model, a car is permanently linked to its wheels

Alternative 2: In our model, we can buy new wheels, or even swap wheels between cars Wheels can exist without cars

Car Wheel1 0..*

Car Wheel0..1 0..*

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14Association Instance Relationship: Association A person subscribes to zero or more magazines A magazine has zero or (hopefully) more subscribers The connection is not as close as between a car and its wheels

May name an association (or composition / aggregation)

Person Magazine

Person Magazinesubscribes

0..* 0..*

0..* 0..*

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15Other UML Diagrams