Introduction to the Object-Oriented Paradigm

Object-Oriented Paradigm and UML 1

Introduction to the Object-Oriented Paradigm


Objectives

• To explain the essential difference between the procedural and object-oriented (OO) paradigms

• To summarize the advantages and disadvantages of the OO paradigm

• To explain the basics concepts of the OO paradigm: objects, classes, attributes, and operations


The Procedural Paradigm• Operations are

separate from data but manipulate it.

• Example: A stack data type– Data store (array,

linked list)– Separate operations

for pushing, popping, etc.

Data

Operations


The Object-Oriented Paradigm• Data is packaged

(encapsulated) with the operations that manipulate it.

• Example: a stack object– Data store within a

stack object– Operations within the

stack object

Operations

Data


Encapsulation Advantages 1• Problem and solution similarity—

Software objects are like real-world things.

• Abstraction—Data structures and algorithm details are ignored in design.

• Information hiding—Implementations can be truly hidden.(Shielding the internal details of a program unit’s processing from other program units)


Encapsulation Advantages 2• Coupling—Operations are not related

through shared data structures.(The degree of connection between pairs of modules)

• Cohesion—It’s easier to keep related operations and data together.(The degree to which a module’s parts are related to one another)


Encapsulation Advantages 3• Reusability—It’s easier to reuse objects

than collections of operations and various data structures.

• Scalability—Objects can be of arbitrary size.

• New features—The object-oriented paradigm offers new and powerful ways of doing things, as we will see.


Problems with the OO Paradigm

• It’s a lot more complicated than the procedural paradigm.– Harder to learn– Harder to use properly


Objects

An object is an entity that has properties and exhibits behavior.An object is an entity that has

properties and exhibits behavior.

• Things are encapsulated when they are packaged together in a container.

• Objects encapsulate properties and behavior.• Ideally, objects model things in the world.

– Example: Traffic simulation


Attributes and Operations

An attribute is a named data value held by an object or a class.

An operation is a named object or class behavior.

A feature is an attribute or operation.

An attribute is a named data value held by an object or a class.

An operation is a named object or class behavior.

A feature is an attribute or operation.


Attribute and Operation Examples

lane1

maxSpeed = 25length = 2.3

addVehicle()getClearDistance()getMaxSpeed()

lightA

NSgreenTime = 35EWGreenTime = 65amberTime = 10

tick()getAmberTime()getNSColor()

car54

color = redlocation = lane1distance = 1.22

tick()stop()go()


Object Characteristics

• Every object has its own attributes and operations, though these may be the same as some other objects.

• Every object has a unique identity.– Two objects with the same attributes

holding the same values and behaviors are distinct.


Messages

• Objects communicate by sending one another messages.

• Messages are abstractions of function calls, signals, exceptions, etc.

• Ideally, objects send messages that model real-world communications between things.– Example: Traffic simulation


Classes

• Classes have attributes and operations.• A class is not a set of objects—it is more

like a blueprint or a specification.• Objects are said to be instances of classes.

An class is an abstraction of a set of objects

with common attributes and operations.

An class is an abstraction of a set of objects

with common attributes and operations.


Examples of Classes

Lane

maxSpeedlength

addVehicle()getClearDistance()getMaxSpeed()

TraficLight

NSgreenTimeEWGreenTimeamberTime

tick()getAmberTime()getNSColor()

Vehicle

colorlocationdistance

tick()stop()go()


Classes and Abstract Data Types• ADT: a set of values (the carrier set) and

a collection of operations to manipulate them

• A class forms a type but not an ADT• Mathematical entities that can be

implemented procedurally or using the OO paradigm

• OO techniques provide an excellent way to implement ADTs


UML Class and Object Diagrams


UML

• Unified Modeling Language• Developed by Grady Booch, Ivar

Jacobson, and James Rumbaugh (the three amigos) at Rational Software Corporation (1994)– Goal to produce a standard OO analysis

and design notation

• Now a standard controlled by the Object Management Group (OMG)


UML Names

• A name in UML is character string that identifies a model element.– Simple name: sequence of letters, digits, or

punctuation characters– Composite name: sequence of simple names

separated by the double colon (::)

• Examples– Java::util::Vector– veryLongNameWithoutPunctuationCharacters– short_name


UML Class Symbol

Phone

numbercolor

java::util::Random

nextBoolean()nextDouble()nextFloat()nextInt()nextLong()setSeed()

Table

Book

authortitleISBN

ring()dial()redial()hangUp()

ExceptionsnoNumberExceptionlowPowerException


Attribute Specification Format

name : type [ multiplicity ] = initial-value

• name—simple name, cannot be suppressed• type—any string, may be suppressed with the :• multiplicity—number of values stored in attribute

– list of ranges of the form n..k, such that n <=k– k may be *– n..n is the same as n– 0..* is the same as * – 1 by default– if suppressed, square brackets are omitted

• initial-value—any string, may be suppressed along with the =


Examples

• weight

• weight : real = 40.0

• signal[*] : real = { 0.0 }

• charge[3,5,7..10]

• hour = 12


Operation Specification Format

name( parameter-list ) : return-type-list

• name—simple name, cannot be suppressed• parameter-list

– direction param-name : param-type = default-value– direction—in, out, inout, return; in when suppressed– param-name—simple name; cannot be suppressed– param-type—any string; cannot be suppressed– default-value—any string; if suppressed, so is =

• return-type-list—any comma-separated list of strings; if omitted (with :) indicates no return value

• The parameter-list and return-type-list may be suppressed together.


Examples

• rotate()

• rotate( degrees : real )

• rotate( in degrees : real = 0.0 ) : Boolean

• rotate( inout degrees : real )

• print( s : String[*] ) : void

• split( s : String ) : int, String[*]


Attribute and Operation Examples

Player

roundScore : int = 0totalScore : int = 0words : String[*] = ()

resetScores()setRoundScore( in size : int )findWords( in board : Board )getRoundScore() : intgetTotalScore() : intgetWords() : String[*]

WaterHeaterController

mode : HeaterMode = OFFoccupiedTemp : int = 70emptyTemp : int = 55

setMode( newMode : Mode = OFF )setOccupiedTemp( newTemp : int )setEmptyTemp( newTemp : int )clockTick( out ack : Boolean )


Class Diagram Uses

• Central static modeling tool in object-oriented design

• Can be used throughout both the product and engineering design processes


Object Diagrams

• Object diagrams are used much less often than class diagrams.

• Object symbols have only two compartments:– Object name– Attributes (may be suppressed)


Object Name Format

• object-name—simple name• class-name—a name (simple or composite)• stateList—list of strings; if suppressed, the

square brackets are omitted• The object-name and class-name may both

be suppressed, but not simultaneously.

object-name : class-name [ stateList ]


Object Attribute Format

• attribute-name—simple name

• value—any string

• Any attribute and its current value may be suppressed together.

attribute-name = value


Examples of Object Symbols

:Rectangle

a1 t:Telephone

b:Book[checked out]

width = 720height = 320color = blue

title = “Ivanhoe”author = “Sir Walter Scott”

x = 10y = 14

number = 8792460color = blackstatus = ONHOOK


Object Diagram Uses

• Show the state of one or more objects at a moment during execution

• Dynamic models as opposed to class diagrams, which are static models(A static model represents aspects of a program that do not change during execution.)(A dynamic model represents aspects of a program that change during execution.)


UML Diagram Tree

Diagram

StructureDiagram

BehaviorDiagram

Class Diagram

ComponentDiagram

Composite StructureDiagram

Deployment Diagram

Object Diagram

Package Diagram

Interaction Diagram Activity Diagram Use Case DiagramState Machine

Diagram

Sequence Diagram

CommunicationDiagram

Interaction OverviewDiagram

Timing Diagram


Procedural vs. Object-Oriented Thinking


Stack of int ADT

• Carrier set: set of all stacks of ints– Empty stack– #0, #1, #2, …– #00, #01, #10, …– …

• Operations: push(), pop(), top(), isEmpty(), isFull(), …


Procedural Approach

• Determine a way to represent the elements of the carrier set (a data structure)

• Determine how to implement the operations (procedures)

• Implement the data structure and procedures in code


C stackOfInt Implementation

struct StackOfInt

int store[CAPACITY]topIndex = 0

createStackOfInt()deleteStackOfInt()push()pop()top()isEmpty()isFull()

• stackOfInt.h• stackOfInt.c• main.c


Object-Oriented Approach• Encapsulate the carrier set and the

operations in a class

• Determine how to implement the carrier set and operations

• Implement the class in code


Class Design

IntStack

store

push()pop()top()isEmpty()isFull()


C++ IntStack Implementation

• IntStack.h• IntStack.cpp• main.c

IntStack

int store[CAPACITY]topIndex = 0

push( v : int )pop() : inttop() : intisEmpty() : BooleanisFull() : Boolean


Example: Ph Monitor

• pH sensors in a vat are monitored

• A control chart is generated


Procedural Approach

• Make a context diagram

• Make data flow diagrams

• Make ERDs

• Make a structure chart

• Implement the code


pH Monitor Context Diagram

UserVat Sensors

control chart

chart parameters

Process pH Monitoring

System

pH readings


pH Monitor Data Flow Diagram

pH readings

1CollectSample

sample sample

window size

chart parameters

current chartparameters

control chart

new chartparameters

new sample sequence

Vat Sensors

2Form Sample

Sequence

Chart Parameters

Samples Sample-Sequence

3Create Control

Chart

sample sequence

User

4Update Chart Parameters


pH Monitor Structure Chart

main

collect sample

read sensor

create chart

display chart

get chart paramters

change chart

parameters

get sample

sequence

pH readingsensor num

window sizechart

parameters

sample sequence

control chart control

chart


How to describe Requirement Result on OO?• Use UML diagram

• Sometime you can use Use Case diagram as the first diagram.

• Move into another diagram as needed.


Use Case Diagram

Change Chart

Display Chart

Collect Sample


pH Monitor Class Diagram

UserPanel

alterUCL( )alterLCL( )alterCL( )alterSize( )

ChartUCL : realLCL : realCL : realsize : integer

setUCL( )setLCL( )setCL( )setSize( )display( )

SysClock

getTime( )

SampleList

size : integer

append( )getSize( )getTail( )setToFirst( )getNext( )

SampleMgr

wakeUp( )

SensorphReading : real

getReading( )

Samplepoint : integer[*]time : TimeisFailed : Booleanmean : real

takeReadings( )getTime( )isFailed( )getMean( )


Thank you

Documents

Introduction to the Object-Oriented Paradigm