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Modeling Methods

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Modeling Methods

How to structure the

problem?

Model

Is a presentation of reality. Just a picture is worth a thousandof words, most system models are pictorial representations

of reality.

SAMP

LEFLO

ORPLAN

The answer is just

Simple, use MODELS

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Models

Logical Models Physical Models

Show what a systemis or does?

Show not only what asystem is or does? But

also how the system is

implemented.Other names:

Implementation Model

Technical model

Other names:

Essential modelConceptual model

Business model

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Process Modeling

Process ModelingIs a technique for organizing and documenting the

structure and flow of data through a systems Processes ,policies, and procedures to be implemented by a

systems Processes.

Context DiagramIllustrate the systems interface to the business and

outside world, including other information systems.

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Process Modeling

Context Diagram

Library System

Member

Librarian

SupplierAdmission card

Application

Whole system as one process

E.g. Context Diagram of a Library System

Shows the major data flows into

and from the application, and the

system boundaries.

System boundary

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Process Modeling

Shows the top level function defined to cover the scopeof the application. It also shows the major data flows into

and from the application, and the system boundaries.

Top level function is then decomposed to its component

functions (5-9 typically).

Context Diagram

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Process Modeling

Process ModelsDFD (data flow diagram)

Data flow diagram (DFD)DFD is a tool that depicts the flow of data through a

system and the processing performed by that system.

Order

Invoic

e

Delivery notes

Supplier

Purchasing

Dept.

Stores

Document Flow Diagram can be the

Starting point

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Process Modeling

Gane and Sarson Symbols

Pay a bill

Rounded rectangleRepresent processes or work to be

done. E.g.: pay a bill, withdraw money,etc..

BankSquareRepresent external agent. E.g.: bank,

supplier, creditor, etc..

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Process Modeling

Bank Accounts

Open end box

Represent data store which is sometimes called files.

E.g.: bank, supplier, creditor, etc..

ArrowsRepresent data flows or input and

output. E.g.: payment, bill, withdraw,etc

The above notation is called Gane and Sarson.There are several competing symbols set for DFDs.

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Process Modeling

processA process is work performed on, or in response to,

incoming data flows or conditions.

Input

Hrs. 52, Rtae Rs.20

Output

0

Salary Rs. 1040Payroll

Feed back

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Process ModelingProcess DecompositionIs a act of breaking a system into its component

subsystems, processes, and sub processes.

0

UCSC System

1

Payroll sub system

2

Registration sub System

1.1

Process2.1

Process

1.2Process

2.2Process

1.1.1Sub Process

1.1.2Sub Process

1.1.1.1

1.1.1.2

Therearedif

ferentstyleof

decompositio

ndiagrams.

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Process ModelingProcess Decomposition

AdvantagesImprovedCommunication

Analysis

Design.

Decomposition continues until the functions reach

elementary level. (cannot be further decomposed)

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Process Modeling

Example:Consider a system in a bank whereby account

holders get their withdrawals affected.

Whenever an account holder wants to withdraw

some cash, he presents a cheque or withdrawal slip.

The account is checked for appropriate balance.

If balance exists, the cash is paid and the account

is updated.

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Process ModelingProcess DescriptionThe name of the process is insufficient to explain the logic

to implement the process.

Processes in the system specification should be specified in

such a way that they can be converted to computer program.

I am Kamal.How can I?Hey! Not enough

tell more.

Use process

description methods.

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Process Modeling

Methods of process description Structured English Decision Tree

Decision Table

Process Description

If my IT marks more than 70 then grade is Distinction

Else if mark more than 40 then PassElse Fail

IT Subject

Distinction* >70

* >40Pass

Fail

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Process Modeling

Structured English

Syntax is very similar to block structured languages.

Process Descriptions

Example:

IF credit limit exceeded

THENIF Customer has bad payment history

THEN refuse credit

ELSE

IF PURCHASE ABOVE Rs.1000/=THEN refuse credit

ELSE refer to manager

ELSE allow credit

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Process Modeling

Decision Tree


Credit limitexceeded

Credit limit not

exceeded Allow credit

Bad payment history Refuse credit

Good payment

History

Purchase below Rs.1000/=

Purchase above

Rs 1000 Refuse credit

Refer to Manager

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Process Modeling

Decision Table


X

Y

NN

X

N

YN

XXXX

XRefer Manager

XRefuse

N

NN

Y

YN

N

NY

Y

NY

N

YY

YPurchase above Rs.1000/=

YGood payment history

Allow Credit

YCredit limit exceeded

Conditi

on

Actio

n

Y-TRUE N-NOT TRUE X-TAKE ACTION

Better way of describing logic involving multiple condition

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Process ModelingData flowsData flows are the communication between processes and thesystem environment.

Data flowRepresent an input of data to a process or the output of data (or

information) from a process

Data flow symbol

Data flow name

Data flow names should be descriptive noun and noun phrases

that are singular. E.g. Order not Orders

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Process ModelingControl flowRepresents a condition or non data event that triggers a process.

Control flow symbol

Control flow name

I have to get up@ 5.00 a.m.

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Process ModelingIllegal vs. legal data flow

548B1 B2

88B1

8B1DS1

8DS1 DS2

B1 B1P1

B1 DS1P1

B1DS1 P1

DS1 DS1P1

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Example : DFD

Consider a system in a bank whereby account holders

get their withdrawals affected.

Whenever an account holder wants to withdraw some

cash, he presents a cheque or withdrawal slip.

The account is checked for appropriate balance.

If balance exists, the cash is paid and the account is

updated.

Process Modeling

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Withdrawal

Acknowledge

Account

Holder

Cheque/Withdraw

al Slip

Account

Holder

Example

Step 1 - Context Diagram

Using Gane and Sarson, notation

Bank

Payment

System

Process Modeling

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Withdrawal Acknowledge

Account

Holder

Cheque/Withdrawal Slip

Account

Holder

Valid

Balance

Current

BalanceNew

Balance

1Verify

A/C

Balance

2

Debit

Withdrawal

AmountAccount Master

Example

Step 2 - First Level DFD

Process Modeling

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Data ModelingA model is a representation of reality.

Logical model Physical model

Logical functions describe any changes

of value made by the processes on logicaldata.

Whereas logical functions more closely

mirror the subject world.

Logical DFDs only illustrate what occurs

without showing how it occurs.

Physical-level functions are closer to the

usage world (real world).

Usually a physical device is used to

transform data. E.g. Computer, person,

etc.

Physical DFDs show things happen, or

the physical components.

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Data ModelingEntity Relationship DiagramsDepicts data in terms of the entities and relationships

described by data.

Entities

An entity is something about which the business needs tostore data. Synonyms entity type and entity class

Example:

Employee Paris Ball Payment Concepts

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Data Modeling

Entity:is a class of

Persons Places Objects Events Concepts

An entity instance is a single occurrence of an entity. Every

entity must have an identifier or key to uniquely identifyeach instance.

about which we need to capture and store data.

Entity Relationship Diagrams

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Data Modeling

Symbol:

Consider Martin notations.

DEPARTMENTEMPLOYEE

The named rounded rectangle represent the entity.

A line represent the relationship.


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Data Modeling

Attribute:is a descriptive property or characteristics of an entity.Sometimes called as element, property, and field.

A key is an attribute, or group of attributesthat assumes a unique value for each entity

instance. It is some time called an identifier.

EMPLOYEENIC_NO

Name

Address

Age

.

.

.

This person can be identified using his ID number.


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Compound Attribute is one that actually consist of otherattributes.

Synonyms- composite attribute,

concatenated attributedata structure.

Example : Address

Street Address

City

Country

Postal Code

Data Modeling


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The values for each attribute are defined in terms of threeproperties:

1. Data type What type of data can be stored in that

attribute.2. Domain What values an attribute can legitimately take on.

3. Default Is the value that will be recorded if not specifiedby the user.

Data Modeling


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RelationshipsNatural business association that exists between one or

more entities

May represent an event that links the entities or logicalaffinity that exits between the entities.

E.g.. an EMPLOYEE assigns to a JOB

EMPLOYEE Assigns

Data Modeling

Person married relationEntity Relationship Diagrams

JOB

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Cardinality

Defines the minimum and maximum number of occurrences

of one entity that may be related to a single occurrences of

the other entity.

or

Exactly one

Data Modeling

Person married relation

Exam

ple:


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I might bemarried or not

Data Modeling

I may havesome friends or

none

Entity Relationship DiagramsCardinality

Zero or one

Zero, one or more

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Data ModelingEntity Relationship Diagrams

Cardinality

I have to work at

least one, or more

projects.

I am working on

many projects.

One or more

More than one

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DegreeNumber of entities that participate in the relationship

Degree =1

Recursive Relationship Relationship that existsbetween different instances of the same entity.

Data Modeling

EMPLOYEE

Supervise


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Degree =2

Binary Relationship - When two different entitiesparticipates in a relationship

Data Modeling

DEPARTMENT EMPLOYEEWorks for


Degree

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Degree =3

Ternary or 3-ary Relationship -When more than two different

entities participates in a relationship.

Data Modeling

PROJECT EMPLOYEE

LOCATION

ASSIGNMENT


Degree

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Object Modeling

IntroductionThe object oriented approach differs from structured

systems analysis and design.

Thus, rather than modeling systems by data flows, E-Rdiagrams or process descriptions, all three components

are integrated together into objects.

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Object Modeling

Introduction

In Object Analysis you do not need to think in terms of

building one large system.

Instead we identify objects as independent entities having

their own local goals.

Such objects exchange messages between themselves

to achieve a global goal of the large system.

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Object Modeling

Introduction

What is an Object?

Objects are the elements through which we understand theworld around us.

Objects have

recognizable identities or properties (what it knows)

and

particular behaviors or methods (What an object does)

These identities and behaviors enables us to recognize

them as discrete things

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Object Modeling

Human is an object

Properties

Skin tone

Height

Weight

Etc

Behavior

Smile

Run

Walk

Etc

Ball,Sticka

reotherob

jects

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Introduction

The object oriented approach differs from structured

systems analysis and design.

Thus, rather than modeling systems by data flows, E-R

diagrams or process descriptions, all three components

are integrated together into objects.

Data model

E-R ModelData flow

Object Modeling

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Object Modeling

Object-oriented analysis (OOA)

OOA is a technique used to:

Reuse existing components

Define new or modified objects that will be

combined with existing objects

In order to produce useful business computing application.

Reuse

New Modify

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Object Modeling

Object modeling (OM)OM is a technique for identifying objects within the

systems environment and the relationships betweenthose objects.

Class room

Identified objects in class room

Teacher Book

Chair Student

Etc

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Object ModelingClassA class is a set of objects that share common attributesand behavior. A class is sometimes referred to as anobject class.

Smile ( )

Run ( )

Study ( )

Name

Age

Grade

Student

Stud

entC

lass

Open()

Close()

ISBNauthortype

title

copyright

Book

Book

Cla

ss

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Object Modeling

Generalization/Specialization

Person

Teacher Student

Smile ( )

Run ( )Eat ( )

Name

Age

Gender

PersonGeneralization/specializa

tion is a technique whereinthe attributes and

behaviors that are common

to several types of objectclasses are grouped into

their own class, called a

supertype. The attributes

and methods of thesupertype object class are

then inherited by those

object classes.

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Object Modeling


Person

Teacher Student

Smile ( )

Run ( )Eat ( )

Name

Age

Gender

Person

A class supertype is anobject class whose

instances store attributes

that are common to one ormore class subtypes of the

object.

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Object Modeling


Person

Teacher Student

Smile ( )

Run ( )Eat ( )

Name

Age

Gender

Person

A class subtype is anobject class whose

instances inherit some

common attributes from aclass supertype, and then

add other attributes that

are unique to an instance

of the subtype.

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Subtype

Supertype

Example:

Object Modeling


Non Academic

Staff

Academic Staff

Postgraduate Under Graduate

StudentStaff

Department

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UML Representation of Generalization/Specialization

Department

Name

ID

T.P No:

Address

Approval()

Sent()

Receive()

Staff

Name

IDT.P No:

Address

Submit()

Sent()

Student

Name

IDT.P No:

Address

Schedule set()

Lecture()

Arrowhead

indicates

Generalization/

Specialization

relationship

Object Modeling


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Object Modeling

Object/Class relationship

is a natural business association that exists between

one or more objects/classes. Although objects can be developed independently of

other objects, they also have a relationship to other

objects. One such relationship is to use a link directly from one

object to another : Association

Example: There are many student in the each class

Class Student1 1 *

Studies

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Multiplicity defines how many instances of one

object/class can be associated with one instance of

another object/class.

Multiplicity

Library Books1 1 *

Object Modeling

Allthelibra

ryhavi

ngalo

tofbo

oks

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Multiplicity

Object Modeling

Works for

DepartmentEmployee1Works for

DepartmentEmployee

1 orleave blank

I am working for

one and only

departmentExactly one - 1

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Object Modeling

Some customers

are paying much

but some are not

0..*Makes PaymentCustomer

PaymentCustomerMakes *

Zero or more 0..*

Multiplicity

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Object Modeling

I am married

0..1HasSpouseEmployee

I am not married

Zero or one 0..1

Multiplicity

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Object Modeling

CourseUniversityOffers

1..*

We offer one or more

courses

One or more 1..*

Multiplicity

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Object Modeling

GameTeam7..9Has

sch

eduled

Brazil 2004

We have to play 7 to

9 games in 2004

In year 2004 BRAZIL have to play 7, 8, or 9 games

Specific range 7..9

Multiplicity

Games

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Aggregation Relationship

Object Modeling

ChapterBook

Composition Aggregation Relationship

- Indicates Composition Aggregation Relationship

1..*

SADforBIT

There are no books

without chapter

1..*

Black filled diamond

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Object Modeling

PlayerTeam

Shared Aggregation Relationship

Indicates shared


0..*

0..*Team may have

Ronaldo or not

Diamond without filled

0..*

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Message

Object Modeling

A Message is passed when one object invokes one or

more of another objects methods to request informationor some action.

Dog can run & catch

Catch the cat

The catch message callcatch() method of dog

then the catch method

automatically call the run

method.

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Polymorphism

Object Modeling

It mean that the same named behavior may be completed

differently for different objects.

Polymorphism means many forms applied to object

oriented technique.

Op

enaslid

ingdoo

r

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ARCHITECTURAL PLAN

Object Modeling

Unified Modeling Language (UML)Only a notation that is now widely accepted as a standard

for object modeling.

UML DiagramsGives five different groups of diagrams to model a system.

These deferent diagrams provides the development team adeferent perspective of the information system.

ELEVATIONFLOOR PLAN

Example: Well known Housing industry where they use lot of diagrams.

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Object Modeling

UML Diagrams

Use Case Diagrams

Graphically describe who will use the systems and in whatways the user expects to interact with the system.

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Object Modeling

UML Diagrams

Class Diagrams

Shows object classes that the system is composed of as wellas the relationship between those objects.

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Object Modeling

UML Diagrams

Object Diagrams

Similar to class diagrams, but instead of depicting objectclasses, they model actual object instances.

Provide snap shot of the systems objects at one point in time

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Object Modeling

UML Diagrams

Sequence Diagram

Graphically depict how object interact with each other viamessages in the execution of a use case or operation.

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Object Modeling

UML Diagrams

Collaboration Diagrams

Similar to sequence diagrams but do not focus on the timingor sequence of messages. Instead they represent the

interaction between the objects in a network format.

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Object Modeling

UML Diagrams

State Diagrams

Use to model the dynamic behavior of particular model. Theyillustrate an objects life cycle. During the life cycle the object

can change to various states.

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Object Modeling

UML Diagrams

Activity Diagrams

Graphically depict the sequential flow of activities of either abusiness process or use case.

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Object Modeling

UML Diagrams

Components Diagrams

Used to graphically depict the physical architecture of thesystem.

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Object Modeling

UML Diagrams

Deployment Diagrams

Describe the physical architecture of the hardware andsoftware in the system.

Documents

IT1402e