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Simbol Dasar
Empat Simbol Dasar
Kotak rangkap dua digunakan untuk menggambarkan 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
Customer Inquiry
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
D1Customer Master
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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 Diagrams Advantages
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 is used to create a data flowdiagram by providing a framework forobtaining processes, input, output, and
data stores required for user activities A use case shows the steps performed
to accomplish a task
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Use Case
The major sections of a use case are
Use case name
DescriptionTrigger
Trigger type
Input name and sourceOutput name and destination
Steps performed
Information required for each step
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Partitioning
Partitioning is the process of analyzinga data flow diagram and deriving a
series of manual procedures andcomputer programs
A dashed line is drawn around a group
of processes that are included in eachcomputer program or manual procedure
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Manual Procedures
A manual procedure is performed bypeople
Manual processes have manual inputand manual output
Computer processing not used with
manual processes
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User Interface
A user interface represents a screen, adata entry operation, a report, or some
other means for persons to interact witha computer
It occurs when the data flow links a
manual and an automated process
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Reasons for Partitioning
The reasons for partitioning a data flowdiagram into separate computer
programs areDifferent user groups should have different
programs
Processes that execute at different timesmust be in separate programs
Processes may be separated into differentprograms for security
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Reasons for Partitioning
Similar tasks may be included in thesame program
Several batch processes may beincluded in the same program forefficiency
Several processes may be included inthe same program or job stream forconsistency of data
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Using Data Flow Diagrams
Data flow diagrams can be used forseveral different purposes:
Unexploded data flow diagrams are usefulto identify information requirements
Exploded data flow diagrams can be used
for presentation, education, and gatheringfeedback information from users
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