1. CHAP-1 OBJECT ORIENTED SYSTEM DESIGN (IT-703)
Text Books: 1. Object Oriented System Development Ali Bahrami (TMH)
2. Object-Oriented Modeling & Design with UML
Blaha & Rambaugh (Pearson)
3. Object-Oriented Analysis & Design using UML
D Jeya Mala, S Geetha(TMH)
4. Object-Oriented Analysis, Design and Implementation
Brahma Dathan, Sarnath Ramnath (University Press)
OOSD- Introduction

2. An overview of object-Oriented Systems Development
OOSD- Introduction

3. Project estimation (under estimation) Time, effort estimation
Q. What major problems have you encountered during past software projects?
Project estimation (under estimation)
Time, effort estimation
Premature implementation
Quick prototyping the problem
Feeling of understanding problem but really not
Changing requirements
(Waterfall model,
Incremental model,
Evolutionary development model,
Agile model)
OOSD- Introduction

4. System development activity consists of
Introduction
Software development is dynamic
1. Always undergoes major changes Current and future practice will be different Anticipate the methods and tools to succeed Can not predict the future
Today, vast number of tools and methodologies are available for systems development.
System development activity consists of
Systems analysis,
modeling,
design,
testing,
implementation, and
maintenance.
OOSD- Introduction

5. A software (SW) development methodology is a series of processes, if followed, can lead to the development of an application.
Each process consists of number of steps and rules to be followed during development.
Unified Approach is the methodology used by Dr. Ali Bahrami for learning OOSD.
OOSD- Introduction

6. Two Orthogonal views of the SW
Object-Oriented systems development differs from Traditional development techniques. Traditional technique view the SW as a collection of programs (or functions) and isolated data.
What is a program?
Niklaus Writh, inventor of Pascal, sums it up
Algorithm + Data Structure = Program
A SW system is a set of mechanism for performing certain action on certain data
There are two different ways to view software constructions either on functions or on data
OOSD- Introduction

7. Data centered - data store (e. g
Data centered - data store (e.g. file or database) lies at the center of this architecture and is accessed frequently by other components that modify data

8. Data flow - input data is transformed by a series of computational or manipulative components into output data

9. Object-oriented - components of system encapsulate data and operations, communication between components is by message passing
Layered - several layers are defined, each accomplishing operations that progressively become closer to the machine instruction set

10. The distinction between Traditional system development methodologies and newer Object-oriented methodologies lies in their primary focus.
1. Traditional approach focuses on the functions of the system
– What is it doing ?
2. Data is free flowing.
OOSD Methodology:
Object-oriented system development centers on the object.
Views software in the form of objects which are discrete and grouped.
OOSD focuses on the object, which combines data and functionality
3. Primary focus is on data.
4. Data security is given utmost attention.
OOSD- Introduction

11. OOSD Methodology
OOSD is a way to develop software by building self-contained modules or objects that can be easily replaced, modified and reused.
OOSD encourages views of the world as a system of cooperative and collaborating objects. (e.g. Window)
In an O-O environment software is a collection of discrete objects that encapsulate their data as well as the functionality, to model real-world entity.
In an O-O system everything is an object and each object is responsible for itself.
Don’t say “system is computing the payroll of employee”, you tell the employee object “ compute your payroll”.
OOSD- Introduction

12. Why an Object Orientation?
O-O systems are :
Easier to adapt to changing requirements
Easier to maintain
More robust and promote greater design
Code reuse
Say
System, compute the payroll of this employee (Traditional way)
Now tell the employee object
Compute your payroll (In object orientation way)
OOSD- Introduction

13. Object Orientation is appropriate
To develop complex systems
Systems that are prone to change
Systems with user interfaces
Systems that are based on client/server model
To build e-commerce / web based applications
For enterprise application integration (EAI)
OOSD- Introduction

14. Reasons why object orientation works:
Higher level of abstraction. (at object level)
Traditional: Top down approach supports abstraction at function level)
Data is now attributes and function is method
Seamless transition among different phases of software development.
O-O uses same language like UML (Unified Modeling Language) to talk about all phases of software development.
It reduces complexity, redundancy, and creating a robust system.
Encouragement of good programming technique.
Promotion of reusability.
Seamless approach reduces the level of complexity and redundancy and makes for clearer, more robust system development.
OOSD- Introduction

15. Overview of the Unified Approach
The Unified Approach (UA) is a methodology for software development that is proposed by the author Dr. Ali Bahrami. (and used in this book of OOSD)
The UA is based on methodologies by Grady Booch, James Rumbaugh & Ivar Jacobson. They tried to combine the best practices, processes & guidelines along with OMG’s(Object Management Group’s) UML.
The heart of UA is Jacobson’s use-case. Use case represents a typical interaction between a user and a computer system to capture the user’s goals and needs.
This book of OOSD uses a Layered Architecture (LA) to develop applications.
OOSD- Introduction

16. Layered Architecture (LA)
LA is an approach to software development that allows us to create objects, that represents tangible elements of the business, independent of how they are represented to the user through an interface or physically stored in a database.
Layered Approach consists of:
i. View or UI (User Interfaces) Layer
ii. Business Layer
iii. Access Layer
OOSD- Introduction

17. The Unified Approach Road Map
Analysis Design
Identify the user 6. Apply design axioms
Develop a simple to design classes
business model 7. Design the access
3. Develop use case layer
Interaction diagram 8. Design view layer
Develop sequence diagrams classes
Develop collaboration diagram Macro level UI design
5. Classification Micro level UI design
Identify classes Usability and user satisfaction
Identify relationships Refine and iterate
Identify attributes
Identify methods (Fig.1.1 pg.7, Ali Bahrami)
OOSD- Introduction

18. The software development process Building high-quality software
Goals for OOSD
The software development process
Building high-quality software
Object-oriented systems development
Use-case driven systems development
Prototyping
OOSD- Introduction

19. Advantages of OOSD Code and design reuse Increased productivity
Ease of testing (?) and maintenance
Better understandability
Elegant design:
Loosely coupled, highly cohesive objects
Essential for solving large problems.
OOSD- Introduction

20. Initially incurs higher costs
After completion of some projects, reduction in cost become possible
Using well-established OO methodology and environment:
Projects can be managed with 20% to 50% of traditional cost of development.
OOSD- Introduction

21. The Journey of OOSD begins....
Summary
The OOSD is an iterative process and is divided into analysis, design, prototyping/implementation, and testing.
The UA, Layered Architecture and UML are used by Dr. Ali Bahrami for OOSD.
The Journey of OOSD begins....
OOSD- Introduction