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Simbol Dasar

Empat Simbol Dasar

Kotak rangkap dua digunakan untukmenggambarkan suatu entitas eksternal (bagian

lain, suatu perusahaan, seseorang, atau sebuahmesin) yang dapat mengirim data atau menerimadata dari sistem

Tanda panah menunjukkan perpindahan data dari

satu titik ke titik yang lain Bujur Sangkar dengan sudut membulat digunakan

untuk menunjukkan adanya proses transformasi

Bujur sangkar dengan ujung terbuka yang

menunjukkan penyimpanan data

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Entitas Eksternal

Entitas Eksternal mungkin

orang, seperti CUSTOMER atau STUDENT

Sebuah perusahaan atau organisasi,seperti BANK atau SUPPLIER

Departemen lain di dalam perusahaan

seperti ORDER FULFILLMENTSistem atau subsistem lainnya seperti

INVENTORY CONTROL SYSTEM

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Proses

Mewakili baik:

Keseluruhan sistem

sebuah subsystem

Pekerjaan yang diselesaikan, sebuah aktifitas

Nama harus dalam bentuk kata kerja-kata benda- kata sifat

Kata kerja menggambarkan jenis kegiatan seperti menghitung,menverifikasi, menyiapkan, mencetak atau menambahkan. Katabenda menunjukkan hasil utama proses seperti laporan, record.Kata Sifat mengilustrasikan keluaran yang mana seperti urutan ke

belakang atau inventarisasi. Contoh nama-nama proses yang lengkap ialah menghitung pajak

penjualan, memverifikasi status rekening konsumen, menyiapkaninvoice pengapalan, mencetak laporan yang diurutkan ke belakang,mengirim konformasi email ke konsumen, memverifikasi neracakartu kredit, menambah record inventaris

1

Add NewCustomer

2

CustomerInquiry

Subsystem

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Penyimpanan Data

Nama dengan sebuah kata benda, menggambarkandata

Penyimpanan data biasanya diberikan sebuah nomorreferensi unik seperti D1, D2, D3

Termasuk dalam penyimpanan data seperti:

Sebuah File Komputer atau database

Sebuah File Transaksi Sebuah kumpulan tabel

Sebuah file record manual

D1CustomerMaster

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Aliran Data

Menunjukkan data tentang orang, tempat,atau sesuatu bergerak diantara sistem

Nama harus sebuah benda menggambarkanpergerakan data di antara sistem

Kepala panah menunjukkan arah aliran

Gunakan double headed-arrows hanya ketikasebuah proses membaca data danmengupdate data pada tabel atau file yangsama

Customer Record

New Customer

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Developing Data FlowDiagrams

Use the following guidelines:

Create the context level diagram, including

all external entities and the major dataflow to or from them

Create Diagram 0 by analyzing the major

activities within the context processInclude the external entities and major data

stores

Create a child diagram for each complex

process on Diagram 0

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Creating Data Flow Diagrams

Detailed data flow diagrams may bedeveloped by

Making a list of business activities

Analyzing what happens to an input dataflow from an external entity

Analyzing what is necessary to create anoutput data flow to an external entity

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Data Flow Diagram Levels

Data flow diagrams are built in layers

The top level is the Context level

Each process may explode to a lowerlevel

The lower level diagram number is thesame as the parent process number

Processes that do not create a childdiagram are called primitive

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Diagram 0

Diagram 0 is the explosion of thecontext level diagram

Should include up to 7 or 9 processes

Any more will result in a cluttered diagram

Processes are numbered with an integer

The major data stores and all externalentities are included on Diagram 0

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Child Diagrams

Each process is numbered with theparent diagram number, a period, and a

unique child diagram numberExamples are:

3.2 on Diagram 3, the child of process 3

5.2.7 on Diagram 5.2, child of process 5.2

On Diagram 3, the processes would benumbered 3.1, 3.2, 3.3 and so on

3.2

Edit

Customer

5.2.7

CalculateCustomer

Discount

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Child Diagrams

External entities are usually not shownon the child diagrams below Diagram 0

If the parent process has data flowconnecting to a data store, the childdiagram may include the data store as

well

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Data Flow Diagram Errors

The following conditions are errors thatoccur when drawing a data flow

diagram:A process with only input data flow or

only output data flow from it

Add

New

Customer

1

Add

New

Customer

2

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Data Flow Diagram Errors

Data stores or external entities areconnected directly to each other, in anycombination

Customer D1 Customer

Vendor D2 Vendor Master

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Data Flow Diagram Errors

Omitting data flow from the diagram

Unbalanced decomposition between a

parent process and a child diagram

The data flow in and out of a parentprocess must be present on the child

diagram

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Logical Data Flow Diagrams

Logical data flow diagrams show howthe business operates

They have processes that would existregardless of the type of systemimplemented

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Data Flow DiagramProgression

The progression of creating data flowdiagrams is

Create a logical DFD of the current systemNext add all the data and processes not in

the current system which must be presentin the new system

Finally derive the physical data flowdiagram for the new system

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Logical Data Flow DiagramsAdvantages

Advantages of logical DFDs are

Better communication with users

More stable systems, since the design isbased on a business framework

Increased understanding of the business

by analystsThe system will have increased flexibility

and be easier to maintain

Elimination of redundancy

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Physical Data Flow Diagrams

Physical data flow diagrams include

Temporary data stores and transaction files

Specifying actual document and file names

Controls to ensure accuracy andcompleteness

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Triggers and Events

An input flow from an external entity issometimes called a trigger, since it

starts activitiesEvents are activities that happen within

the system

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Event Tables

An event table is used to create a dataflow diagram by analyzing each event

and the data used and produced by theevent

Every row in an event table represents

a unique activity and is used to createone process on the data flow diagram

C d l

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Use Case and Data FlowDiagrams

Creating a use case is another approachused to develop a data flow diagram

A use case