01. object web - ooad i

8/8/2019 01. Object Web - OOAD I

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Object Oriented Programming

Object WebBapayya Choudhary Maganti

2-2-647/182/J, C. E. Colony, New Nallakunta, Hyderabad

- 500 013.- - -


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Course Contents

Object Oriented BackgroundObject Oriented Programming Concepts

Analysis

Use Case Modeling

DesignObject Modeling

CRCClass Diagrams

Dynamic ModelingSequence Diagram

Collaboration DiagramState Diagrams

Activity Diagrams

Component Diagram

Deployment DiagramCase Stud Drawin Editor Problem


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Background


2-2-647/182/J, C. E. Colony, New Nallakunta, Hyderabad

- 500 013.- - -


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What Is Object Orientation?

Term Object-Orientation means.The organization of software as a collection of discrete

objects that incorporate both data structure and behavior.

A new technology based on objects and classes.Use of objects and classes in analysis.

Everything here is object and process is sending a

message to objects.

A language is object oriented if supports the following

four proprieties:

Abstraction.

Polymorphism.

Encapsulation.

Inheritance.


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Object-based Vs Object-oriented

Object-based programming usually refers toobjects without inheritance and hence without

polymorphism.

These languages support abstract data types

and not classes, which provide inheritance and

polymorphism.Object-oriented programming refers to the

objects with inheritance and polymorphism.


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What Is the Background?

Arrived from Process.

Talk about the Behavior Centric not Data Centric.

Simula 67 the first Object Oriented Language, 1967.

Objects, Classes, Inheritance, Dynamic Typing.

Smalltalk first Pure Object Oriented Language, 1969.

Classes, Objects, Inheritance.Dynamic Typing.

First Graphics Environment.

First Use of Mouse in Programming Environment.

Introduced first Multi Threaded Environment.

Form Parc of Xerox Corporation.

For more info look at parc.xerox.com.


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OO Programming Languages

Statically-typed:Memory allocation at compile time

No Runtime Class, Objects

Type Defined.

Example: C++

Dynamically-typed:

Memory Allocation at Run-time

Runtime Classes, Object

Runtime Inheritance

No Data types

Example: Smalltalk

Both:

Example: Java


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Statically-Typed:

C++

Classic-Ada

Dragoon

Emerald/Jade

Object Pascal

Trellis/Owl


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Dynamically-Typed:

Actors Language

C+@

Flavors

Python

Self

Smalltalk


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Both:

Actor

Ada95

BETA

C++ (With RTTI)

Cecil

CLOS

Eiffel

Java

Modula-3

Objective-C

Sather


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Object-Oriented Operating Systems

Object-Oriented Operating Systems provideresources through objects, sometimes all the

way down to to the machine.

These are almost always distributed systems

(DOS or DPOS), allowing objects to be passed

freely between machines.


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Object-Oriented Operating Systems

Some of the Object-Oriented OperatingSystems:

Apertos.

Chorus Micro-kernel.

Choices.

GEOS.Mach.

NachOS.

Ouverture Project.

Peace.

Spring.


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Object-Oriented Databases

Object-oriented databases are databases thatsupport objects and classes.

They are different from the more traditionalrelational databases because they allow

structured sub objects, each object has its own

identity, or object-id and because of support formethods and inheritance.


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Object-oriented Databases

It is also possible to provide relationaloperations on an object-oriented database.

OODBs allow all the benefits of object-orientation, as well as the ability to have a

strong equivalence with object-oriented

programs, an equivalence that would be lost ifan alternative were chosen, as with a purely

relational database.


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List of Object-oriented Databases:

Research Systems AVANCE

CLOSQL

ConceptBase*

COOL/COCOON

Encore*

Exodus*

Machiavelli

MOOD4-PC*

OBST/STONE*

Ode*

Oggetto

Orion

OTGen

PLOB

VODAK

Commercial Systems ArtBASE, EasyDB

GemStone

ITASCA, Matisse

NeoAccess

OBST+

O2, Objectivity

ObjectStore

Ontos

Odapter/OpenODB program (HP)

Unisys Universal Repository

Versant VisualWorks

OOFILE

Phyla, POET

Statice UniSQL


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Object-oriented Methodologies

List of Methodologies:Bernard

BON

BoochCoad/Yourdon

Colbert

de ChampeauxEmbley

EVB

Rebecca WirfsFUSION

HOOD

IBM

Jacobson

Martin/OdellOoram

Room

RumbaughShlaer and Mellor

Open

UMLWasserman

Wirfs-Brock


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UML

Collection of concepts from variousmethodologies.

From:BOOCH.

RUMBAUGH.

JACOBSON.

Started in 1995.

Adapted by OMG.

Current Version 1.3.

Can be adapted for any application.


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UML, Stepping ahead

Unified Method 0.8

Start 1/95, OOPSLA 10/95

Booch OMT

UML 0.9, 0.916/96, 9/96

OOSE Others

UML 1.0OMG Submission 1/97

UML Partners Expertise

UML 1.1

OMG Revision 9/97Adoption 11/97

Others

UML 1.3RTF report 4/99

OMG Feedback

UML 1.?Expected Shortly

OMG/RTF Revisions


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Object Oriented Programming

Concepts - Fundamentals


2-2-647/185, C. E. Colony, New Nallakunta, Hyderabad - 500 013.

Phone: +9140-7422414, E-mail: [email protected], Web: www.objweb.com


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What is an Object?

The entity which represents somethingObjects is having a concrete physical form as

well as intelligence, because we not onlyperceive them but also make them do

something.

Physical ObjectAn object may be invisible to the human eye

but having some basic form of intelligence.

Conceptual Object


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SBI/K

Object have State, Behavior, Identity andKnowledge about Other Objects

State is attributes

Behavior is methods

Identity is uniqness

Knowledge is message sent between to objects.

State

BehaviourIdentity

x=50, y=50

isFirstQuadrantPoint ( )Point Object at memory AF00Knowledge


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Identity

Each Object is different form other.All Objects Have Identity.

Identity is that property of an object thatdistinguishes it from all other objects. (Booch).

An object is a reality and it is an entity which

exists in time and space. We are able toidentify it as an object because of its

IDENTITY. This is true for all objects in the real

world.

We see a lion as a lion and not a horse

because of its identity.


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Identity

If we look at any two similar object, thepossible outer look may be same but there may

be lot of difference between them.

My be two pens are appearing same, but the

are different.

Similarly, two identical twins are nothing buttwo distinct objects.


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Objects Know Each Other

Objects can't behave independentlyLike humans objects need to know about other

objects in the system.

All objects are intelligent

We give them levels of intelligence we would

normally associate with humans.Objects are not in isolation

We share the world around us with other objects.


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Objects Communicate With Each Other.

Objects live in a dynamic world where theyexchange information and communicate with anumber of objects getting certain things done.

When a object receives the messages and ifthe object cannot understand the informationthen it searches for the object which can

understand this and send this message to theother object.

There are two types of communicationsbetween objects.The direct communication.

The indirect communication.


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Behavior

By communication an operation was achieved.The operation placed a certain

RESPONSIBILITY.

A property is gives uniqueness to Object.

The term property denotes attributes.

Both property and attribute may be used

interchangeably.

Properties are usually static, which means thatthey do not change over a period of time.


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Behavior

Attributes have values.An attribute is a data value held by the objects

in a grouping of similar objects.

It is important to note here that ATTRIBUTE

SHOULD BE A PURE DATA VALUE NOT AN

OBJECT. (Not valid for pure object orientedprogramming languages.)

Unlike objects, data values have no identity.


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State

Preceding each of these state - change is a stimulus(Booch) or event (Rumbaugh) or action (Booch).

Therefore, the current state of any object depends on:

Preceding State.

Object's inherent properties (or attributes).

Stimulus received by the object. Which may cause the

properties to undergo changesCurrent Status =

Inherent Properties +

Preceding State +

Stimulus received +

Argument Passed with Stimulus.


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State

The State of an object may be defined as:The state of an object at any given instance is determined

by the combination of its precedent status, its internalproperties, the current values of these properties and the

stimulus it receives.The fact that every object has a state implies that every

object takes up some amount of space (either in thephysical world or in computer memory).

Now we can define Behavior of an object as:Behavior is how an object acts or reacts in terms of its state

changes and message passing.

Colloquially the word object is also used to indicate agroup of similar objects.Instance Object -> Instance.

Class Object -> Class.


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Important Aspects

An object with the same name may occur incompletely different domains.

Ex: Customer.

An object is characterized by what it is used for

and by the information that is attached to it.

i.e., attributes.Use of an object is captured by its behavior.

i.e., by the operation that it can offer to other object

in its environment.

C S f O


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Client Server Nature of Objects

An object uses another object for performingan operation by sending a stimulus.

Each stimulus has an unique name that clearly

determines the operation to be performed.

The requirements placed on the server object may

have several responsibilities depending upon its

use.

Client Object Server Object

Cli t S N t f Obj t


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Client Server Nature of Objects

When a client objects sends a stimuli to a server object, theonly information that is available to the client object is the

type of operation that can be performed by the server

object.

The client knows only the name of the operation to be

performed by the server which is sent as the stimuli along

with various types of information each operation needs in

order to perform the task.The names and types of information are called the

operations 'signature'.

Remember an object can perform different operations

depending upon usage, and, therefore will have different

'signatures'.

The combination of all such signatures of an object is called

the objects protocol.

Obj t D i ti


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Object Description

An object can be described in two different, butrelated ways.

The external description, which shows how

others can use the object and the responsibilitiesthe objects has towards others. This description

contains only the objects protocol (how it can be

used). This is also sometimes called the objectsspecification.

The internal description specifies the objects

various attributes and how each operation isrealized. This description is called the objects

implementation.

A di t B h


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According to Booch

Without this conception framework, you maybe programming in a language such asSmalltalk, object Pascal, C++, CLOS, Eiffel,

Ada, but your design is going to smell like aFORTRAN, Pascal or C application.

You will have missed out on or otherwise

abused the expressive power of the object-oriented language you are using forimplementation.

More importantly, you are not likely to havemastered the complexity of the problem athand.

R l t d C t


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Related Concepts:

Important concepts & Related Topics:Abstraction.

Encapsulation.

Generalization.Concurrence.

Persistence.

Polymorphism.

Composition.

Factorization.

Delegation.

Refinement.

Multi-layer Architecture.


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Abstraction

View of the ObjectObject Web, Bapayya Choudhary Maganti

Abstraction


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Abstraction

One of the two ways humans cope withcomplex problems to spot

Similarities between objects, processes, situations.

Break down large problems into manageable level.

A viewer abstracts objects in relation to the problem

perspective.

Let us consider an example of how 'human beings' may

be viewed in different domains.

Domain Viewer Abstraction

Biology Biologist SpeciesPolitics Politician Vote Bank

Industries Manager Resource

Food habits Man-eater Food

Abstraction


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Abstraction

Abstraction is a phenomenonBy which a viewer is able to identify unique

features or characteristics of an object which

separate the object from all other objects in a givenproblem domain.

There are four metrics to ensure the design of

class hierarchy and relations are:

Coupling

CohesionSufficiency

Completeness


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Cohesion


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Cohesion

Cohesion measures the extent of connectivityamong the elements of a single object or class.

The most desirable form of cohesion is the

FUNCTIONAL COHESION.i.e. We check if elements comprising an abstraction

are truly representative of the behaviors.

You can't abstract an animal and a vehicle ifthey don't serve the same semantic purpose.Both animal and vehicle may be abstracted in the

class LoadCarrier but cannot be abstractedtogether if we are looking at a race horse and apassenger car.

Sufficiency


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Sufficiency

This means that the class captures in itsabstraction all the expected behavior of the

class for meaningful interaction.

For example

if we are designing a class 'UpdateItem', it makes

sense to include an operation that will add an itemor remove an item or modify an item.

Though this may sound very routine, it has been

noticed that many times we neglect or miss out toinclude all the operations.

Completeness


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Completeness

This has two formsExtension of sufficiency

A complete class or module is one whose interface is

general enough to be commonly usable to any client.In other words the interface should be such that it covers

all aspects of the abstraction.

Extension of generalizationThe class should have implemented all the expected

abstract or virtual functions of the super class.

The class hierarchy is considered to complete when allthe sub classes are defined and the sub-classes are

defined as per the minimum expectations of the super

class.

The Process of Abstraction


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The Process of Abstraction

Booch saysClasses and objects should be at the right level of

abstraction;

Neither too high nor too low.

The process of abstraction, is incremental anditerative.We study the problem domain

Identify objects which may seem disparate in the beginning Identify their relationship and group them in different classes

based on their common characteristics.

The identification of abstractions involvesKnowledge of the problem domain

Discovery

Invention.


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Encapsulation

Hide for right Abstraction & CouplingObject Web, Bapayya Choudhary Maganti

Encapsulation


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Encapsulation

Encapsulation actually means to capsulate.A capsule means something held in a covering.

What is inside can not be seen.Enclose something or Encapsulate something

inside the object.

Public

PrivateProtected

... Encapsulation


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... Encapsulation

Abstraction takes care of what an object cando i.e., the various operations it can perform

Encapsulation takes care of how it does it i.e.,

the attributes and the implementation details.

All objects have two parts

The abstracted visible part - INTERFACEThe encapsulated hidden - IMPLEMENTATION

What Is Achieved by Encapsulation?


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What Is Achieved by Encapsulation?

Encapsulation is the process of hiding therepresentation of an abstraction that make up

the structure of a class of objects and their

behavior.

If the implementation is modified we continue

to use the object without any modifications tothe interface.

According to Booch.

Intelligent encapsulation localizes design decisionsthat are likely to change.

Refactoring


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Refactoring

In Refactoring is the process of changing theobject without changing the Interface.

Interface is public method defined in Class

Note:

If an Object need implementation to be modified

without changing the interface it is terms adRefactoring.

This may not be possible always.

Refactoring minimizes the changes on other object.This process ensures that the classes have right

level of coupling and will have minimum/no impact

on the collaborating classes.

Achieving Encapsulation


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Achieving Encapsulation

Smalltalk.By default all attributes are private and methods are public.

It is only documentation process to achieve private

methods.Java.

Variables and methods can be declared as private public

and protected.Can have package level access modifiers and can mark

classes as private to package.

Can define inner classes, which have class scope.

C++.

Variables and methods can be declared as private, public

and protected.

Can have private, protected, public inheritance.

Why Public, Protected and Private


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Why Public, Protected and Private

Attributes of classMake sure that all attributes are declared as private

and give protected or public access modifiers (get

and set methods)

Methods of class

Make sure that all methods are declared as

protected (never private) and only those required

as public.

Different levels of EncapsulationCollaboration level

Inheritance level

Package level

Level of Encapsulation


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p

Collaboration levelBetween two classes there exists public and private

methods where the collaborating class can access

only the public behavior of other class but not theprivate behavior.

Inheritance level

Sub class is extension to the existing behavior ofthe super class and it should be able to access allthe behavior of the super class.

Package levelClasses can be defined as public or private to

package and this should minimize the couplingbetween the packages.


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Inheritance

Specialization & GeneralizationObject Web, Bapayya Choudhary Maganti

Generalization and Inheritance.


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Generalization and Specialization areimportant aspects of Object Orientation which

give rise to the concepts of HIERARCHY and

INHERITANCE.

Each individual object in a class is called an

INSTANCE of its class.The terms 'instance' and 'object' are

interchangeable (for C++)

Car Van

FourWheeler

... Generalization


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An instance of a subclass is simultaneously aninstance of all its ancestor classes.

Each subclass not only inherits all the features

of its superior class, but adds its own specific

attributes and operations as well. It may

augment or restrict the existing structure andbehavior of a super-class.

Classes are related to one another via

inheritance relationships.

... Generalization


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The most specialized class in a hierarchy isknown as the leaf class.

The most generalized class is known as the

base class.

The leaf classes are also known as concrete

classes.Only the leaf class (or concrete class) will have

instances.

The base class and other intermediary classes

usually do not have any instances.

... Generalization


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Abstract classes are not expected to haveinstances of their own.

Abstract classes are written with the

expectation that its subclasses will add to itsstructure the behavior which implements

methods.Single inheritance means each subclass has

exactly one super-class.

Multiple inheritance means each such classhas more than one super-class.

... Generalization


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The terms Generalization, Inheritance andSpecialization refer to the same underlying

idea, and are many a time used

interchangeably.Generalization is used while modeling and

implementation. It facilitates modeling bystructuring classes and capturing what is

similar and what is different amongst classes.

Identify the behavior of different classes


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ShortInteger

Integer Float

Number

LongInteger

Magnitude

CharacterPoint

Solution


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ShortInteger

Integer Float

Number

LongInteger

Magnitude

CharacterPoint

Abstract Methods: +, -, , =, !=

Concrete Methods: +, -,


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Build the hierarchy/classes for the following.

Identify all classes in a coordinate system.

Identify the major responsibilities of the classes.

For a drawing editor problem define the elements.Rectangle.

Has start point, stop point, the diagnoll opposite corners

Line.Has start point, stop point.

Circle.

Has center and radius.

Ellipse.

Has center, major radius, minor radius.

Solution


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ShapeLine

Rectangle

Ellipse

Point

Shape

Line Rectangle Ellipse

Point

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