1. The OO Solution The OO model closely resembles the problem domain
Base your model on the objects in the problem domain
Iteratively refine the high-level model until you have an implementation
Attempt to avoid big conceptual jumps during the development process
CSE 435: Software Engineering

2. Objects VISA State of Michigan J. Q. Public 123 4567 887766 998
Drivers License
State of Michigan A
CSE 435: Software Engineering

3. Attributes and Operations
Person class
J. Q. Public
VISA
Drivers License
State of Michigan A
Attributes
name
age
height
weight
Operations
move
change-job
width
id-number
issue
change
Person objects
Card objects
Card class
abstracts to

4. Characteristics of Objects
Identity
Discrete and distinguishable entities
Classification
Abstract entities with the same structure (attributes) and behavior (operations) into classes
Polymorphism
The same operation may behave differently on different classes
Inheritance
Sharing of attributes and operations based on a hierarchical relationship
CSE 435: Software Engineering

5. The Class Diagrams
CSE 435: Software Engineering

6. Objects
Something that makes sense in the application context (application domain)
J.Q. Public
Joe’s Homework Assignment 1
J. Q. Public’s drivers license
All objects have identity and are distinguishable
NOT objects
Person
Drivers license
CSE 435: Software Engineering

7. Classes
Describes a group of objects with similar properties (attributes), common behavior (operations), common relationships to other classes, and common semantics
Person
J. Q. Public
Joe Smith
D. Q. Public
Card
Credit card
Drivers license
Teller card
CSE 435: Software Engineering

8. Class Diagrams Class diagram Instance diagram D. Q. Public: age= 32
Person
J. Q. Public:
age= 35
Person
Person
age: integer
Class with attributes
Objects with values
Objects have an identity
Do not explicitly list
object identifiers
SSN OK!
CSE 435: Software Engineering

9. Examples
CSE 435: Software Engineering

10. Operations and Methods
Transformation that can be applied to or performed by an object
May have arguments
CSE 435: Software Engineering

11. Object Notation - Summary
CSE 435: Software Engineering

12. Associations Conceptual connection between classes Class diagrams
A credit card is issued-by a bank
A person works-for a company
Issued-by
Credit Card
Bank
Class diagrams
Works-for
Person
Company
J.Q. Public:
Person
Michigan State Univ:
Company
Works-for
Instance diagram
Age=35
CSE 435: Software Engineering

13. Associations are Bi-directional
There is no direction implied in an association (Rumbaugh - OMT)
Country
name
City
name
Has-capital
Person
name
Drivers-license
lic.-number: integer
Is-issued
CSE 435: Software Engineering

14. Associations Have Direction
Unified adds a direction indicator
Inconsistently used
Country
name
City
name
Has-capital
Person
name
Drivers-license
lic.-number: integer
Is-issued
CSE 435: Software Engineering

15. Multiplicity
One person holds one credit card
name: String
Person
card-number: integer
Credit-card
Holds
One object can be related to many objects through the same association
One person can hold zero or more credit cards
Person
Holds
0..*
Credit-card
name: String
card-number: integer
CSE 435: Software Engineering

16. Multiplicity (Cont.)
One person can hold zero or more credit cards (0..*)
Each card has zero or one holder (0..1)
Person
Credit-card
0..1
Holds
0..*
name: String
age: integer
card-number: integer
card-number=
Card789:Credit-Card
:DQPublic:Person
name= D. Q. Public
age=32
:JQPublic:Person
name= J. Q. Public
age=35
Holds
Holds
card-number=
Card456:Credit-Card
card-number=
Card123:Credit-Card
CSE 435: Software Engineering

17. Higher order associations
Ternary association
Project, language, person
Seldom needed (and should be avoided)
1..*
1..*
Language
Project
1..*
Person
Compiler: Project
C++ :Language
Note: hexagons should be
rectangles to represent
instances
J. Q. Public:Person
Age=35
TicTacToe:Project
LISP:Language
CSE 435: Software Engineering

18. Link Attributes How to represent salary and job title?
Associations can have properties the same way objects have properties
How to represent salary and job title?
Person
Company
name: String
0..*
Works-for
age: integer
name: String
SSN: integer
address: String
address: String
Person
Company
name: String
0..*
Works-for
age: integer
name: String
Use a link attribute!
SSN: integer
address: String
address: String
salary: integer
job-title: String
CSE 435: Software Engineering

19. Folding Link Attributes
Why not this?
Salary and job title are properties of the job not the person
Person
name: String
Company
age: integer
0..*
Works-for
SSN: integer
name: String
address: String
address: String
salary: integer
job-title: String
Person
Company
name: String
0..*
Works-for
0..*
age: integer
name: String
In this case, a link attribute is the only solution
SSN: integer
address: String
address: String
salary: integer
job-title: String
CSE 435: Software Engineering

20. Role Names
Attach names to the ends of an association to clarify its meaning
name: String
age: integer
SSN: integer
address: String
Person
Company
Works-for
0..*
salary: integer
job-title: String
employer
employee
boss
worker
Manages
0..1
CSE 435: Software Engineering

21. Aggregation A special association, the is-part-of association
A sentence is part of a paragraph (a paragraph consists of sentences)
A paragraph is part of a document (a document consists of paragraphs)
0..*
0..*
Document
Paragraph
Sentence
Aggregation symbol
CSE 435: Software Engineering

22. Aggregation (Cont.) Often used in parts explosion Car 4 Wheel Body
Gearbox
Engine
1..*
1..*
0..*
Door
Hood
Trunk
Piston
Valve
Crankshaft
CSE 435: Software Engineering

23. Generalization and Inheritance
The is-a association
Cards have many properties in common
Generalize the common properties to a separate class, the base-card
Let all cards inherit from this class, all cards is-a base-card (plus possibly something more)
issue()
revoke()
height: integer
width: integer
thickness: integer
id-number: integer
Card
expire()
class: vehicle
issued: date
expires: date
Drivers License
ID Card
validate()
credit-limit: integer
Credit Card
CSE 435: Software Engineering

24. Example Owns Pilot City Airline Works-for Based-In 0..* name name name
license
Located-In
Offers
1..*
Certified-On
Pilots
0..*
0..*
Airport
0..*
Plane
0..*
name
Departs
0..*
Flight
model
date
serial #
heat()
Arrives
Used-For
flight #
hours flown
clean()
0..*
cancel()
heat()
delay()
refuel()
clean()
30..*
0..*
Seat
Passenger
location
name
Confirmed-for
reserve()

25. Aggregation Versus Association
Can you use the phrase is-part-of or is-made-of
Are operations automatically applied to the parts (for example, move) - aggregation
Not clear what it should be……
0..*
0..*
Company
Division
Department
Works-for
0..*
Person
CSE 435: Software Engineering

26. Aggregation Versus Inheritance
Do not confuse the is-a relation (inheritance) with the is-part-of relation (aggregation)
Use inheritance for special cases of a general concept
Use aggregation for parts explosion 4
Wheel
Body
Car
Gearbox
Engine
Minivan
Compact
Jeep
Roll Bar
CSE 435: Software Engineering

27. Recursive Aggregates
A recursive aggregate contains (directly or indirectly) an instance of the same kind of aggregate
Program
Simple
Statement
Compound
Block
0..*
CSE 435: Software Engineering

28. Class diagram Metamodel I
Eclipse.org
CSE 435: Software Engineering

29. Class diagram Metamodel II
CSE 435: Software Engineering
Science direct

30. Use Case Metamodel I uu: use case association relationship
_i: includes
_e: extends
_g: generalization
aa: actor relationship
Image: Science Direct: ``Visual Modeling for Software Intensive Systems, Kooper et al, 2006.
CSE 435: Software Engineering

31. Use Case Metamodel II
CSE 435: Software Engineering
Image: Jot.fm

32. Object Modeling Summary
Classes
Name
Attributes
Operations
Associations
Roles
Link attributes
Aggregation
Inheritance
CSE 435: Software Engineering