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ObjectObject--Oriented Software EngineeringOriented Software Engineering
Chapter 1
An Introduction to
Object-Oriented Software
Engineering
Object-Oriented Systems Development Bahrami © Irwin/ McGraw-Hill
What is Object-Oriented Software
Engineering ?....
Object-Oriented Software Engineering is the process of
solving customers’ problems by using the Object-Oriented
concepts and the systematic development and evolution of
large, high-quality software systems within cost and time.

3
Two Orthogonal views of software
 The StructuralStructural
 "part of" hierarchy, functions
 concentrate on actual components
 concrete
 The Object OrientedObject Oriented
 "is a" hierarchy
 concentrate on kinds of components
 abstract
4
A View of the Two paradigms

5
A View of the Two paradigms
6

What is a Software development
methodology?
•Practices, procedures, and rules
used to develop software.
Systems Development
Methodologies
• Systems Development methodology is
a way to develop system.
• A Comprehensive System
Development methodology utilizes sets
of tools as well as the style in which they
are to be used.

Object Oriented System
Development methodology
• Object-Oriented Systems Development is a
way to develop software by building self-
contained modules that can be more easily:
• Replaced
• Modified
• and Reused.
Traditional Systems
Development Methodology
• Traditional or Structured approach is
based on the idea that a system can be
thought of as a collection of modules
or subsystems.
• It is much easier to work with a
smaller cohesive (inter-related)
module than a complex system.

Object-Oriented Systems
Development Methodology
•In an O-O environment, Software
is a collection of discrete objects.
•These objects encapsulate their
data and functionalities to model
real world "objects."
Development Approach
Iteration and Reuse
Build use-case
model
Validate/ Test
O-O Analysis
Build
Use-Cases
Design classes,
define
attributes and
methods
O-O Design
O-O
Implementation
Using TOOLS
CASE and/or
OO programing
languages
User
satisfaction
Usability &
QA Tests
Build object
& dynamic
model
Object
analysis
Build UI
and
prototype
User satisfaction test,
usability test
quality assurance test
Validate/
test

Object-Oriented Environment
In an object-oriented environment,
software is a collection of discrete
objects that encapsulate their data
and the functionality to model
real-world objects
Development Methodology (Con’t)
•An object-oriented life cycle
encourages a view of the world as
a system of cooperative and
collaborating agents.

15
What Object Oriented…?
Object Orientation
is about viewing and modelling the real
world / system as a set of interacting
and interrelated objects
Features of OO Approach:
 The universe consists of interacting
objects
 Describes and builds systems
consisting of objects
Benefits of Object Orientation
• An Object orientation produces
systems that are easier to evolve
(develop), more flexible, more robust,
and more re-usable than other
Traditional approaches
• Faster development,
• Re-Usability,
• Increased quality,
• and easier maintenance.

Towards Object Orientation
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Unified Approach
•The unified approach (UA) is a
methodology for software
development.
•The UA, based on methodologies
by Booch, Rumbaugh, Jacobson,
and others, tries to combine the
best practices, processes, and
guidelines.

Unified Approach (Con’t)
•UA utilizes the Unified Modeling
Language (UML) which is a set of
notations and conventions used to
describe and model an
application.
Layered Architecture
•UA also uses a layered architecture
to develop applications.
•The layered approach consists of
view (or) user interface, business,
and access layers.

Layered Architecture (Con’t)
•This approach reduces the inter-
dependence of the user interface,
database access, and business control.
•Therefore, it allows for a more robust
(healthy/ strong) and flexible system.
An object oriented philosophy

Class and Object
Class and Object
24

Class and Object

27
Identification of Attributes
• Attributes express some important aspects of the
objects in the problem domain
Leg
Leg
Body
Arm
Arm
Head
A model of a B
Body can be
composed of
these objects.
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JohnJohn
Identification
of Attributes
Identification
of Behaviors
ShafiShafi JohnJohn MaryMary

29
Identification
of Attributes
Identification
of Behaviors
ShafiShafi JohnJohn MaryMary
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Inheritance
Class of PersonsClass of Persons

31
Inheritance
Class of PersonClass of Person
AttributesAttributes
Name
Address
Age
Profession
BodyBody
Left Leg
Right Leg
Left Hand
Right Hand
Head
BehaviorBehavior
Tell Age
Store Age
Jump
Walk
Dance
…….
Create an InstanceCreate an Instance
Create Left Leg
Create Right Leg
Create Head
Create Left Hand
Create Right Hand
Class PersonClass Person
Instance of
Instance of
Instance of
3 November 2014R. MD. Shafi, Associate Professor in CSE
32
Step-4: Inheritance Contd…
Class BodyClass Body
Left Leg
Right Leg
Left Hand
Right Hand
Head
BehaviorBehavior
Move Right Hand
Move Left Hand
Stretch Right Leg
Bend Left Leg
…………...
Create A BodyCreate A Body
Create Left Leg
Create Right Leg
Create Head
Create Left Hand
Create Right Hand

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Class of PersonClass of Person
Name
Address
Age
Body
Profession
BehaviorBehavior
Tell Age
Store Age
Jump
Walk
Dance
…….
Create A PersonCreate A Person
Create A Body
Class PersonClass Person
Instance of
Instance of
Instance of
Inheritance
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Inheritance: Person-Man-Woman
Husband
BehaviorBehavior
Store Age
Jump
Walk
Dance
…….
Create A WomanCreate A Woman
Create A Person
Female ClassFemale Class
Derived fromDerived from
Person ClassPerson Class
Wife
BehaviorBehavior
Tell Age
Store Age
Jump
Walk
Dance
…….
Create A ManCreate A Man
Create A Person
Male ClassMale Class
Derived fromDerived from
Person ClassPerson Class

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Object Technology Principles
Common Methods of Organization
Abstraction
Encapsulation (Information Hiding)
Inheritance
Polymorphism
Message Communication
Associations
Reuse
36
• Common Methods of Organization
People are accustomed to thinking in terms of...
• color
• price
• weight
• engine
• options...
Objects & Attributes
• number of doors
• number of wheels
• number of windows
• number of lights
• number of bolt type 1
• number of bolt type 2
• etc....
Wholes and PartsGroups & Members
VANS:
• light utility
• utility
• passenger
• etc...

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Abstraction
A mental ability that permits people to view real-world
problem domains with varying degrees of detail
depending on the current context of the problem.
• Helps people to think about what they are doing
• Functional and Data abstraction
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Encapsulation (Information Hiding)
A technique in which data are packaged together with
their corresponding procedures.
 In Object-Oriented Technology the “package” is called an OBJECT
 The interface to each object is defined in such a way as to reveal as little as
possible about its inner workings
 Encapsulation allows [software] changes to be reliably made with limited effort
[Gannon, Hamlet, & Mills, 1987]

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Inheritance
A mechanism for expressing similarity
between things thus simplifying their definition.
• looks
• behavior
•Attitudes etc...
Person
Student Faculty Staff
Inheritance
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Polymorphism (“many forms”)
The ability to hide different implementations
behind a common interface.
The ability for two or more objects to respond
to the same request, each in its own way.
• H2 O = water, ice, steam (liquid, solid, vapor)
• Carbon compound crystallizes as graphite &
diamond

41
Message Communication
OBJECT
OBJECT
OBJECT
OBJECT
Objects communicate via messages

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