1. Object Oriented Modeling and Design
Agenda
Object Oriented Philosophy
Developing an Object-Oriented application
How do you organize a business & OOAD?
Example
Flight booking system
An Object-Oriented Approach
A Payroll Program
Structured Approach

2. Object Oriented Philosophy :
Object basics:
Object Oriented Philosophy :
When developing an Object-Oriented application, two basic questions always arise:
What objects does the application need?
What functionality should those objects have?
OOAD can be illustrated by analogy to how to organize a business

3. Object Oriented Philosophy :
Object basics:
Object Oriented Philosophy :
How do you organize a business & OOAD?
Business Analogy
OOAD
What are the business processes?
Requirements analysis
What are the employee roles?
Domain analysis
Who is responsible for what? How do they interact?
Responsibility assignment, interaction design

4. Object Oriented Philosophy :
Object basics:
Object Oriented Philosophy :
What objects does the application need?
Identifying Objects:
Example
Flight booking system
Assume that the following sentences are summarized by domain experts
Airline companies offer various flights
A flight is open to booking and close again by order of the company
A customer can book one or more flights and for different passengers

5. Object Oriented Philosophy :
Object basics:
Object Oriented Philosophy :
What objects does the application need?
A booking concerns with a single passenger and a single flight.
A booking can be cancelled or confirmed.
A flight has a departure airport and an arrival airport.
A flight has a departure day and time and an arrival day and time.
A flight may involve stopovers in airports.
A stopover has an arrival time and a departure time.
Each airport serves one or more cities.

6. Object Oriented Philosophy :
Object basics:
Object Oriented Philosophy :
What objects does the application need?
Objects : Sentence 1
Airline companies offer various flights
 Airline company, Flight (real world entities)
Objects : Sentence 2
A flight is open to booking and close again by order of the company
 Airline company, Flight (real world entities), Booking
Objects : Sentence 3
A customer can book one or more flights and for different passengers
 Booking, Flight ,Customer
Distinction between customer and passenger?

7. Object Oriented Philosophy :
Object basics:
Object Oriented Philosophy :
What objects does the application need?
Objects : Sentence 4
A booking concerns with a single passenger and a single flight
Booking, Flight , Passenger
Objects : Sentence 5
A booking can be cancelled or confirmed
 Booking
Objects : Sentence 6
A flight has a departure airport and an arrival airport
Airport, Flight

8. Object Oriented Philosophy :
Object basics:
Object Oriented Philosophy :
What objects does the application need?
Objects : Sentence 7
A flight has a departure day and time and an arrival day and time
 Flight
Objects : Sentence 8
A flight may involve stopovers in airports
Flight , Airport, Stopover
Objects : Sentence 9
A stopover has an arrival time and a departure time
Stopover
Objects : Sentence 10
Each airport serves one or more cities
Airport, City

9. Object Oriented Philosophy :
Object basics:
Object Oriented Philosophy :
What functionality should those objects have?
OPERATIONS : Sentence 2
A flight is open to booking and close again by order of the company
Flight:
openBooking
closedBooking
OPERATIONS : Sentence 5
A booking can be cancelled or confirmed
 Booking:
cancel
confirm
Similarly we find all operations

10. A Case Study - A Payroll Program:
Object basics:
A Case Study - A Payroll Program:
Consider a payroll program that processes employee records at a small manufacturing firm. This company has three types of employees:
Managers: Receive a regular salary.
Office Workers: Receive an hourly wage and are eligible for overtime after 40 hours.
Production Workers: Are paid according to a piece rate.

11. A Case Study - A Payroll Program :
Object basics:
A Case Study - A Payroll Program :
Structured Approach:
FOR EVERY EMPLOYEE DO
BEGIN
IF employee = manager THEN
CALL computeManagerSalary
IF employee = office worker THEN CALL computeOfficeWorkerSalary
IF employee = production worker THEN CALL computeProductionWorkerSalary
END

12. A Case Study - A Payroll Program :
Object basics:
A Case Study - A Payroll Program :
Structured Approach:
What if we add two new types of employees?
Temporary office workers ineligible for overtime
Junior production workers who receive an hourly wage plus a lower piece rate.

13. A Case Study - A Payroll Program :
Object basics:
A Case Study - A Payroll Program :
Structured Approach:
FOR EVERY EMPLOYEE DO
BEGIN
IF employee = manager THEN
CALL computeManagerSalary
IF employee = office worker THEN
CALL computeOfficeWorker_salary
IF employee = production worker THEN
CALL computeProductionWorker_salary
IF employee = temporary office worker THEN
CALL computeTemporaryOfficeWorkerSalary
IF employee = junior production worker THEN
CALL computeJuniorProductionWorkerSalary
END

14. A Case Study - A Payroll Program :
Object basics:
A Case Study - A Payroll Program :
An Object-Oriented Approach :
What objects does the application need?
The goal of OO analysis is to identify objects and classes that support the problem domain and system's requirements.
Some general candidate classes are:
Persons
Places
Things

15. A Case Study - A Payroll Program :
Object basics:
A Case Study - A Payroll Program :
An Object-Oriented Approach :
What are some of the application’s classes?
Employee
Manager
Office Workers
Production Workers
Identify class hierarchy
Identify commonality among the classes
Draw the general-specific class hierarchy

16. A Case Study - A Payroll Program :
Object basics:
A Case Study - A Payroll Program :
An Object-Oriented Approach :
FOR EVERY EMPLOYEE DO
BEGIN
employee computePayroll()
END

17. A Case Study - A Payroll Program :
Object basics:
A Case Study - A Payroll Program :
An Object-Oriented Approach :
If a new class of employee were added
FOR EVERY EMPLOYEE DO
BEGIN
employee computePayroll()
END