Transcript CM402 Lecture Week 1 - Northumbria University

IS514 Lecture Week 7
Class Diagrams II
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Slide 1
So far
• Identifying
– Classes
– Attributes
– Operations
• How to draw basic class diagrams
• This week
– Types of relationships
– Multiplicity
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Slide 2
Relationships
• Classes do not exist in isolation
• It is important to consider how they
– Interact
– Relate
• Tend to be VERBS
• Five principal types of relationships
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Slide 3
Type One - Dependency
• Where one class must know about another
• Example:
– Prospective student knows of a course
• Not commonly used
• Used more commonly in design / implementation
– Java – import javax.swing.*;
ProspectiveStudent
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knowsOf
Course
Slide 4
Type Two - Association
• Classes associated with / related to one another
• Example
– Student studies a course
• Very Commonly used
• “Default” type of relationship
Student
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studies►
Course
Slide 5
Type Three - Aggregation
•
•
•
•
Classes made up of other classes
“Part of” relationship
Objects of classes that can exist in their own right
Example
– Student is a member of a seminar group
Student
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memberOf ►
SeminarGroup
Slide 6
Type Four - Composition
•
•
•
•
Class is an integral part of another
“Integral part of” relationship
Object of classes that cannot exist without the other
Example:
– Seminar is delivered for a Module
Seminar
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deliveredFor ►
Module
Slide 7
Type Five Inheritance
• Specialisation / generalisation between two classes
• Example
– Part Time Student is a type of Student
PartTimeStudent
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Student
Slide 8
Creating a Class Diagram
Adding relationships
Ticket
Film
title
producer
length
certificate
genre
for
price
time
film
• Last week we drew a
class diagram for a
Cinema
• Update the diagram to
include the relationship
types
of
AdultPatron
name
age
Patron
is a
name
age
is a
ChildPatron
name
age
buyTicket()
seeFilm()
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Slide 9
One Solution
Film
title
producer
length
certificate
genre
◄ for
Ticket
price
time
film
Patron
of ►
name
age
buyTicket()
seeFilm()
AdultPatron
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ChildPatron
Slide 10
Exercise
• A garage sells cars, accessories and car parts. The
garage sells sport cars, sports utility vehicles and
saloon cars.
• In groups of 3-4 spend 5 minutes
–
–
–
–
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Draw the class diagram for this scenario
Include relationships
Include relationship types
Ignore attributes and operations
Slide 11
One Solution
CarParts
parts
SportsUtility
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Car
accessories
SportsCar
Accessories
SaloonCar
Slide 12
Exercise
• Consider Checkers game.
• Draw the class diagram for
it
– Include relationships
– Include relationship
types
– Ignore attributes and
operations
http://www.darkfish.com/che
ckers/Checkers.html
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Slide 13
Board
Exercise Solution
1
64
Square
BlackSquare
WhiteSquare
On Square
Checker
WhiteChe
cker
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RedChecker
Slide 14
Alternative Naming of relationships
• Role names can be used instead of relationship
names
• Write role name at either end
Board
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+theBoard
+theSquare
Square
Slide 15
Multiplicity
• Relationships have a multiplicity
• Documents how many instances of a class may be
associated with instances of another class
• Numbers placed on relationship to denote
– Minimum
– Maximum
Board
+theBoard
1
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+theSquare Square
64
Slide 16
Multiplicity
• using multiplicity we can specify :– an exact number simply by writing it
– a range of numbers using two dots between a pair of numbers
– an arbitrary, unspecified number using a *
Department
Boss
1
Employee
1..2
1
0..*
Children
1
0..1
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Spouse
Slide 17
Exercise
• Example 1
• A Student takes up to six Modules where at most 25 Students
can be enrolled on each Module. A Student must study at least
one Module. Modules will not run if less than 12 Students
study them.
• Example 2
• An Order has to come from a single Customer and a
Customer may make several Orders over time. Each of these
Orders has several Order Lines, each of which refers to a
single Product.
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Slide 18
Exercise Solutions
Exercise 1
Student
Module
1..6
12..24
Exercise 2
Customer
Order
1..*
What is missing?
1
1
Relationship names
1..n
OrderLine
Product
1
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1
Slide 19
This weeks reading
ESSENTIAL READING
Dennis A, Wixom B, and Tegarden D (2005) System
Analysis and Design with UML version 2 second
edition, Wiley
Chapter 7
Further reading
Bennett, S., McRobb, S. and Farmer, R. (2002) ObjectOriented Systems Analysis and Design using UML,
2nd Edition, McGraw-Hill
Pages 168-176
http://www.agilemodeling.com/artifacts/classDiagram.htm
http://www.omg.org
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Slide 20
Summary
• Types of associations
–
–
–
–
–
Dependency
Association
Aggregation
Composition
Inheritance
• Multiplicity
• Next Week – more class diagrams including
–
–
–
–
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Association Classes
Object Diagrams
Constraints
Visibility
Slide 21