1. UML and Classes, Objects and Relationships [2]
Defining Domain Models Using Class Diagrams

2. Agenda Class Relationships and UML Notations Class Diagram
Association - DONE
Generalization
Realization
Dependency
Class Diagram
Object Diagram
Summary

3. Association - Multiplicity
A Student can take many Courses and many Students can be enrolled in one Course.
Student
Course
takes * *
254: Course
Alice: Student 1.
253: Course
Jill: Student

4. Notes One class can be relate to another in a One-to-one One-to-many
One-to-one or more
One-to-zero or one
One-to-a bounded interval (one-to-two through twenty)
One-to-exactly n
One-to-a set of choices (one-to-five or eight)

5. Notes Multiplicity can be expressed as, Exactly one - 1
Zero or one
Many * or *
One or more *
Exact Number - e.g or 6
Or a complex relationship – e.g , 3..4, 6..* would mean any number of objects other than 2 or 5

6. Association - Self
An association that connects a class to itself is called a self association. 1.

7. Association - Self Employee A Company has Employees.
A single manager is responsible for up to 10 workers.
Employee 1
manager 1.
Responsible
for
worker
0..10

8. Association - Multiplicity
A cricket team has 11 players. One of them is the captain.
A player can play only for one Team.
The captain leads the team members.
Captain
Team
Team
Member
Player 1
0..1 1. 10
member of 1 11
Captain 1
Leads

9. Class Relationships
Association
Generalization
Realization
Dependency

10. Generalization (Inheritance)
Child class is a special case of the parent class
SuperClass
SubClass1
SubClass2

11. Generalization (Inheritance) e.g.
Circle
GraphicCircle

12. Inheritance - Implementation
public class Circle { }
public class GraphicCircle extends Circle {

13. Abstract Class Shape Circle Rectangle
If the class is defined as Abstract no objects of the class can be instantiated.
If at least one method in a class is defined as abstract then the class is abstract.

14. Abstract Methods (Operations)
Shape
draw()
Circle
Rectangle
If the class is defined as Abstract no objects of the class can be instantiated.
If at least one method in a class is defined as abstract then the class is abstract.
draw()
draw()

15. Abstract class and method Implementation
public abstract class Shape {
public abstract draw(); //declare without implementation
……… }
public class Circle {
public draw(){
…….
…..

16. Class Relationships
Association
Generalization
Realization
Dependency

17. Realization- Interface
Interface is a set of operation the class carries out
ctl()
pageDown()
brandName
numOfKeys
Keyboard
TypeWriter
<<interface>>
TypeWriter
ctl()
pageDown()
brandName
numOfKeys
Keyboard
keyStroke() OR
An interface does not have attributes. Only operations.
The computer's keyboard is a reusable interface. Its keystroke operation has been reused from the typewriter. The placement of keys is the same as on a typewriter, but the main point is that the keystroke operation has been transferred from one system to another. Also on computer's keyboard you'll find a number of operations that you won't find on a typewriter (Ctrl, Alt, PageUp, PageDown...) 
The relationship between a class and an interface is called realization.

18. Realization - Implementation
public interface TypeWriter {
void keyStroke() }
public class KeyBoard implements TypeWriter {
public void keyStroke(){
………

19. Class Relationships
Association
Generalization
Realization
Dependency

20. Dependency
Change in specification of one class can change the other class. This can happen when one class is using another class.
Circle
Point
Move(p:Point)

21. Dependency cont
Dependency relationship can be used to show relationships between classes and objects.
circleA:Circle
<<instanceOf>>
Circle
circleB:Circle
<<instanceOf>>

22. Class Diagrams
The UML class diagram consists of several Classes, connected with Relationships.

23. Class Diagram - Example
Draw a class diagram for a information modeling system for a school.
School has one or more Departments.
Department offers one or more Subjects.
A particular subject will be offered by only one department.
Department has instructors and instructors can work for one or more departments.
Student can enrol in upto 5 subjects in a School.
Instructors can teach upto 3 subjects.
The same subject can be taught by different instructors.
Students can be enrolled in more than one school.

24. Class Diagram - Example
School has one or more Departments.
School
Department
has 1
1..*
Department offers one or more Subjects.
A particular subject will be offered by only one department.
Department
Subject
offers 1
1..*

25. Class Diagram - Example
Department has Instructors and instructors can work for one or more departments.
assigned to
1..*
Instructor
Department
Student can enrol in upto 5 Subjects.
Student
Subject
takes *
0..5

26. Class Diagram - Example
Instructors can teach up to 3 subjects.
The same subject can be taught by different instructors.
Instructor
Subjects
teaches
1..*
1..3

27. Class Diagram - Example
Students can be enrolled in more than one school.
Student
School
member *
1..*

28. Class Diagram Example Department School 1…* Instructor Subject Student
has
School
Department 1
1..*
1..*
1…* 1
offeres
assignedTo
member
1..*
1..* *
Instructor
Student
attends
Subject
teaches *
1..5
1..3
1..*

29. Object Diagram Object Diagram shows the relationship between objects.
Unlike classes objects have a state.

30. Object Diagram - Example
c1: Company
name=“UniMelb”
c1: Company
d1: Department
d2: Department
name=“Sales”
name=”CSSE”
manager
employee
p2: Person
p1: Persont
name=“Raj”
name=“Rao”

31. Summary
We have discussed the following concepts and UML notations related:
Association
Generalization
Realization
Dependency
How to create a Class Diagram that contains all the above relationships
Object Diagram for Uni.Dept.system.