what is object-oriented? organization of software as a collection of discreet objects that...

What is Object-Oriented?

Organization of software as a collection of discreet objects that incorporate both data structure and behavior.

Characteristics of Object-Oriented Approach

IDENTITY CLASSIFICATION POLYMORHISM INHERITANCE


IDENTITY

Data is quantified into discrete, distinguishable entities called objects.


Classification

Objects with the same data structure and behavior are grouped into a class.

What is a Class?

A Class is an abstraction that describes properties important to an application.

Each object is an instance of its class.

Classification of Object Oriented Approach

Polymorphism The same operation may behave

differently on differently on different classes.

A specific implementation of an operation by a class is called method.

Classification of Object Oriented Approach

Inheritance Sharing of attributes and operations

among classes based on hierarchical relationship.

A class can be refined into sub-classes. Subclass inherits all the properties of its

superclass and can add own unique properties.

Object Modeling Techniques(OMT)

A methodology for representing the object oriented concepts and development.

Building a model of an application domain and then adding implementation details to it during the design of a system.

STAGES OF OMT

Analysis System Design Object Design Implementation

STAGES OF OMT

AnalysisA concise, precise abstraction of what the desired system must do, not how it will be done.

STAGES OF OMT

System DesignThe target system is organized into subsystems based on both the analysis structure and the proposed architecture.

STAGES OF OMT

Object DesignA design model based on the analysis model but containing implementation details.

STAGES OF OMT

ImplementationObject classes and relationships developed during object design are translated into a particular programming language, database or hardware implementation.

Models used by OMT for System Description

Object Model Dynamic Model Functional Model


Object Model Describes the static structure of the

objects in a system and their relationships.

Contains object diagrams, a graph whose nodes are object classes and whose arcs are relationships among classes.


Functional Model Describes the data value transformations

within a system. Contains data flow diagram, a graph

whose nodes are processes and whose arcs are data flows.


Dynamic Model Used to specify and implement the

control aspects of a system. Contains state diagram, a graph whose

nodes are states and whose arcs are transitions between states caused by events.

Object Oriented Themes

ABSTRACTION ENCAPSULATION COMBINING DATA AND

BEHAVIOUR SHARING


ABSTRACTION Focus on what an object is and does,

before deciding upon the implementation issues.

Allows the same model to be used at different stages of OMT.


ENCAPSULATION Separation of external aspects of an

object, accessible to external environment, from internal implementation details of the object.

It makes the object independent and immune to external changes in implementation.


Combining Data and behavior The caller of an operation need not

consider how many implementations of a given operation exists.


Sharing Object-oriented development allows

information to be shared within application.

It also offers the prospect of reuse of the code and design in future applications.

Difference from Traditional Methods

Places greater emphasis on data structure and lesser on procedural structure.

Adds the concept of class-dependent behavior.