PRESENTED BY- RISHABH SONI

Object – Oriented Design Methodologies

Contents

IntroductionObject-orientationObject-oriented ParadigmObject-oriented developmentObject-oriented methodologiesThe 3 ModelsObject-oriented themesAdvantages of OODReferences

INTRODUCTION

It is a new way of thinking about problems using models based on real world concepts.

The basic construct is object which combines both data structure and behavior in a single entity.

Rumbaugh presents an object oriented software development methodology, the Object Modeling Technique (OMT) which extends from analysis through design to implementation.

INTRODUCTION

Analysis model is built to abstract essential aspects of application domain which contains objects found in application, their properties and behavior.

Then design model is made to describe and optimize the implementation.

Finally the design model is implemented in a programming language, database or hardware.

Graphical notation is used for expressing object-oriented models.

Object - Orientation

The term object-oriented (OO) means that we organize software as a collection of discrete objects that incorporate both data structure and behavior.

Includes 4 aspects:

- Identity

- Classification

- Inheritance

- Polymorphism

OO - Paradigm

An approach to solution to problems in which all computations are performed in the context of objects

A running program can be seen as a collection of objects collaborating to perform a given task.

An OO-paradigm emphasizes modularity and re-usability.

The goal of an object-oriented approach is to satisfy the "open closed principle".

Open Closed principle

The goal of an object-oriented approach is to satisfy the "open closed

principle".

A module is open if it supports extension. If the module provides

standardized ways to add new behaviors or describe new states. In the

object-oriented paradigm this is often accomplished by creating a new

subclass of an existing class.

A module is closed if it has a well defined stable interface that all other

modules must use and that limits the interaction and potential errors

that can be introduced into one module by changes in another. In the

object-oriented paradigm this is accomplished by defining methods that

invoke services on objects.

Object-oriented development

The theme is the identification and organization of application concepts rather than final representation in a programming Language.

OOD approach encourages software developers to work and think in terms of the application domain through most of the software engineering life cycle.

It is a conceptual process independent of a programming language until the final stage.

Object – Oriented Methodologies / OO SDLC stages

The OO methodology has the following stages: System Conception: Software

development begins with business analysts or users conceiving an application and formulating tentative requirements.

Analysis: The analyst scrutinizes and rigorously restates the requirements from the system conception by constructing models. The analysis model is a precise abstraction of what the desired system must do, not how it will be done. Domain & application model

System Conception

Analysis

System Design

Class Design

Implementation

Object – Oriented Methodologies(Contd.)

System Design: the development team devise a high-level strategy – the system architecture – for solving the application problem

Class Design: The class designer adds details to the analysis model in accordance with system design strategy.

Implementation: Implementation translate the classes and relationships developed during class design into a particular programming language, database, or hardware.

3 Models

Object modelDynamic modelFunctional model

Object model

Describes basic structure of objects and their relationship

Contains object diagram

Object diagram is a graph whose nodes are object classes (Classes) and whose arcs are relationships among classes.

Dynamic model

Describes the aspects of a system that change over time.

It specifies and implement control aspects of a system.

Contains state diagram.

State diagram is a graph whose nodes are states and whose arcs are data-flows.

Functional Model

Describes data value transformation within a system.

Contains data flow diagram.

Data Flow Diagram is a graph whose nodes are processes and whose arcs are data flows.

Object-oriented themes/OO Concepts

Abstraction Focus on essential aspects ( what an object does ) Ignore details ( such as how to implement)

OO Themes (Contd.)

Encapsulation Separates external aspects of an object, which are accessible to other

objects, From the internal implementation details, which are hidden from other objects

Prevents ripple effect

OO Themes (Contd.)

Combining Data and Behavior (Polymorphism) Operator polymorphism shifts the burden of deciding what implementation to

use from the calling code to the class hierarchy. The caller of an operation need not consider how many implementations

exist.

Sharing Via inheritance OO development offers the prospect of reusing design and code on future

projects.

Emphasis on the Essence of an object Stresses on what an object is, rather than how it is used Software systems built on object are more stable in the long run.

Synergy Identity, classification, polymorphism, etc. each of these concepts can be

used in isolation, but together they complement each other synergistically.

Advantages of OOD

Used in developing Compilers, Graphics, UI, databases, Object oriented languages, CAD systems, simulations, etc.

Used to document existing programs that are ill-structured and difficult to understand.

Not reduces development time; it may take more time than conventional development because it is intended to promote future reuse and reduce downstream errors and maintenance.

REFERENCES

Object-oriented design and modeling with UML – Michael Blaha and James Rumbaugh

Object-oriented design and analysis – Wikipedia

www.authorstream.com

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