Mata kuliah Analisis dan Desain Sistem Informasi

Data Flow Diagram{Diagram Arus Data}

Arif Akbarul Huda, S.Si, M.Eng

3

● DFDs describe the flow of data or information into and out of a system– what does the system do to the data?

● A DFD is a graphic representation of the flow of data or information through a system

Data Flow Diagrams (DFD)

Flow chart shows “ flow of Control “ . DFD shows “ flow of Data The flowchart describes boxes that

describe computations, decisions, interactions & loops.

It is important to keep in mind that data flow diagrams are not flowcharts and should not include control elements .

DFD is not a “flow chart”

TYPES OF DFD

Data flow diagrams (DFDs) are categorized as either logical or physical. 1) LOGICAL DFD:- A logical DFD focuses on the business and how the business operates. It describes the business events that take place and the data required and produced by each event.

2) PHYSICAL DFD:- A physical DFD shows how the system will be implemented.

DFD COMPONENTS Data Flow Diagrams are composed of the four

basic symbols shown below:-

Process box

D Data Store

ExternalEntity

Data Flow

external entity - people or organisations

that send data into the system or receive data from the system

process - models what happens to the data i.e. transforms incoming data into outgoing data

data store - represents permanent data that is used by the system

data flow - models the actual flow of the data between the other elements

4 Main Elements

1)External Entity:-

The sharp cornered rectangles(or simply

boxes) in a DFD indicates entities.

The External Entity symbol represents sources

of data to the system or destinations of data

from the system.

Entities are people things, organizations etc

EntityEntity

ENTITIES

StudentStudent

DoctorDoctor

TeacherTeacherManagerManager

CashierCashier

UserUserCustomerCustomer

The rounded cornered rectangles in a DFD

indicate processes

The Process symbol represents an activity

that transforms or manipulates the data

(combines, reorders, converts, etc.).

2) Process:-

ProcessProcess

Processes

Accounting System

Accounting System

Grading SystemGrading System

Reservation System

Reservation System

Patient Administration

System

Patient Administration

System

Marketing System

Marketing System

3) Data Store:-

Opened sided rectangles in DFD indicates data store.

The Data Store symbol represents data that is not moving (delayed data at rest).

A Data Store is a repository of data.

Data can be written into the data store. This is depicted by an incoming arrow.

Two data stores cannot be connected by a data flow.

Data can be read from a data store. This is depicted by an outgoing arrow.

External entity cannot read or write to the data store.

Data Store

4) Data Flow:-

Arrow symbol in DFD indicate data flow

The Data Flow symbol represents

movement of data

Data

RULES OF DATA FLOW

• Data can flow from -external entity to process -process to external entity -process to store and back -process to process

• Data cannot flow from -external entity to external entity -external entity to store -store to external entity -store to store

This diagram represents a banking process, which maintains customer accounts.

In this example, customers can withdraw or deposit cash, request information about their account or update their account details.

The five different symbols used in this example represent the full set of symbols required to draw any business process diagram.

EXAMPLE 1

Level 0 DFD• The level 0 DFD (also known as the

context level DFD ) is the simplest DFD.• The outermost level (Level 0) is

concerned with how the system interacts with the outside world.

• This level basically represents the input and output of the entire system.

LEVELS OF DFD LEVELS OF DFD

1. Identify your main system

2. Identify the external people who interact with

the system

3. Decide what data these entities will enter into

the system

4. Determine what these entities expect as

output from the system

How to create Level 0 DFD

Context Level DFD for a Mail Order Business

ORDER PROCESSINGORDER PROCESSINGCUSTOMERCUSTOMERORDER

DELIVERY

The basic module of the system are

represented in this phase and how data

moves through different module is shown.

The level 1 DFD provides a high –level view

of the system that identifies the major

processes and data stores.

Level 1 DFD

1. Focus on your process and break it into 2

or more sub-processes

2. Identify what data flows between these

processes and between the entities

3. Identify What permanent data files are

used in this system

4. Note that no new entities can be

introduced

How to create Level 1 DFD

Delivery

Credit

Status

Level 1 DFD for a Mail Order Business

CUSTOMERCUSTOMERSALES

PROCESSINGSALES

PROCESSING

ACCOUNTING SYSTEM

ACCOUNTING SYSTEM

CUSTOMER DATABASE

Customer no.

Credit Status

ORDERS

Order

Order

Order

Each process from level 1 is exploded even

more into sub processes. This decomposition

continues for each level.

The number of levels possible depends on the

complexity of the system

2-Level DFD and other level of DFD

LEVELLING DFD A context diagram is expanded into a

number of inter-related processes. Each

process may be further expanded into a set of

inter-connected sub processes. This

procedure of expanding a DFD is known as

leveling.

1. With a dataflow diagram, users are able to visualize how the system will operate, what the system will accomplish, and how the system will be implemented

2. Data flow diagrams can be used to provide the end user with physical idea of how the data they input ultimately has an effect upon the structure of the whole system.

3. The old system’s dataflow diagrams can also be drawn up and compared with the new system’s dataflow diagrams to draw comparisons in order to help implement a more efficient system.

The value of a DFD

Order SystemOrder System

OrderSystemCustomer Warehouse

Order

Invoice

New customer

Picking Slip

Order

Ship Statement

New customer

Order SystemOrder System

1

AddCustomer

New info D Customer

1 Master

Customer

2

ProcessCustomer

Order

OrderCust Info

D Back 3 Order

D Inventory 2 Master

BackorderProc Info

3Warehouse Picking

Slip Produced

Pending Order

Packing slip Warehouse

4

Shipping Prepare

D Customer 1 Master

Ship N/A

5

CustomerBill

Produce

Bill N/A

Bill Info

Shipping B/O info

Order

Picked

CustomerShip statement

Cust Bill

Customer

2.1

VerifyCustomer

OrderD Customer 1 Master

Need to establish

Customer

2.2

Verify Item

OrderD Inventory 2 Master

Notify

Valid

2.3

CheckAvailable

2.4

UpdateCommit

2.5

Create Order

D Inventory 2 Master

D Shipping 4 Taxes

D Back 3 Order

Valid Item

Order SystemOrder System

Back Order

Avail

Update

Tax

Ord

Pending Order

Questions ?

Your Assignment

http://en.wikipedia.org/wiki/Physical_Data_Flow

http://www.visual-paradigm.com/product/bpva/tutorials/dfd.jsphttp://www.civil.utm.my/staff/file/141/file/CIMLectureNotes2011.pdfhttp://spot.colorado.edu/~kozar/DFDtechnique.html

http://www.fbk.eur.nl/PRJ/MEETEYEES/dfd.htm

Http://ratandon.mysite.syr.edu/cis453/notes/DFD_over_Flowcharts.pdfhttp://www.slideshare.net/mohit4192/dfd-examples

http://ecourses.vtu.ac.in/nptel/courses/Webcoursecontents/IIScBANG/System%20Analysis%20and%20Design/pdf/module5.pdf

References