Sumber: www.yourdon.com Edited by: Yudi Priyadi Konsep Data Flow Diagram IPO: Input →Process → Output Data→ Process → Information Data flow diagram is a graphical technique that depicts information flow and the transforms that are applied as data moves from input to output. Characteristics of DFD Graphic Partitioned Hierarchic Multidimensional Emphasize flow of data Viewpoint of data and process
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Konsep Data Flow Diagram - whyphi.staff.telkomuniversity.ac.id · •Gane and Sarson symbol set ... A DFD depicts information flow without explicit representation of procedural logic
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Konsep Data Flow Diagram
IPO: Input →Process → Output
Data→ Process → Information
Data flow diagram is a graphical technique that depicts
information flow and the transforms that are applied as
data moves from input to output.
Characteristics of DFD Graphic
Partitioned
Hierarchic
Multidimensional
Emphasize flow of data
Viewpoint of data and process
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The Symbols
DFDs use four basic symbols that
represent processes, data flows, data
stores, and entities•Gane and Sarson symbol set
•Yourdon symbol set
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Symbols for DFD
Data store
Process
name
External
Interactor
External Entity:
Source or destination of data
Process:
Action on data
Data Store:
Storage of data
Data Flow:
Data Transfer
Yourdon notation (sumber: www.yourdon.com)
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Context Diagrams
A context diagram is a top level (also known as Level 0) data flow diagram.
It only contains one process node (process 0) that generalizes the function of the entire system in relationship to external entities.
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Creating a Set of DFDs
Create a graphical model of the
information system based on your
fact-finding results
Performing three main tasks
Step 1: Draw a context diagram
Step 2: Draw a DFD level 1
Step 3: Draw the lower-level diagrams
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Draw a Context Diagram
Drawing Guidelines1. Draw the context diagram so it fits on one
page
2. Use the name of the information system as
the process name in the context diagram
3. Use unique names within each set of symbols
4. Do not cross lines
5. Provide a unique name and reference
number for each process
6. Obtain user input and feedback
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External Entity
External entity represents the sources and
destination of data created by the system.
External entity represents the immediate interface
of the system with the external world.
When an external source of data is also a
destination for data, a loop or occurrence number
may be used.
In case the destination or use of data created by
the process are not known, the flow simply points
outside the system. Similarly, data flows may
originate from “nowhere”.
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Process Boxes
Each processes box in a DFD describes an action
on data.
The Identifier. A number indicating the sequence
of the process.
The Action. A verb specifying the action on
which it is performed on the data.
The Actor or Place. A noun indicating who
performs the action or where it is performed.
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Data Flow Arrows
Data flow arrows link all the process boxes and
data stores in DFDs.
Data flows should be labeled, except in case the
data flows into and out of simple files.
DFDs show only the flow of data, not materials.
A DFD depicts information flow without explicit
representation of procedural logic (e.g.,
conditions or loops).
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Data Store Rectangles
Data stores can be manual files or computer files.
The type of file is not indicated.
Only in case the data store is altered the flow is
not indicated. A simple access is not indicated.
A data store is never the direct recipient of
unprocessed data from external sources or from
other data stores nor is data from a data store
ever directly delivered to an external sources.
There must be a process step in between.
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Examples of Data Stores
Read
Write
Read/
Write
A data item is created
or deleted or updated in the
data store by
a process
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Rules for Constructing DFD
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DFD Not Allowed Flows
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DFD Not Allowed Flows
If part of our system
If not part of our flow ignore
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Data Flows
Only one direction of flow between
processes
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Data Flows
Joins & forks allowed only if exactly the
same data
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Data Flows
Cannot go directly back to the process it
leaves
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Data Flows
Data which moves together should be
shown in a single data flow
itemised calls
invoice
invoicepayment
itemised callsAnd invoice
Pay
Invoice
Telephone
Company
Pay
Invoice
Telephone
Company
invoicepayment
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DFD Rules
Incorrect Correct
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DFD Rules
Incorrect
Correct
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DFD Rules
Incorrect Correct
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Level 0 CD
Origin #1
Destination 2
0
System
a
b
c
z
r
Destination 1
Origin #2
Keterangan:
a: .........
b:...........
c:.......... dst
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Level 1 DFD
1
a
b
c
z
r
2
3
4
5
d
e
f
g h
i
Origin #1
Origin #2
Destination 1
Destination 2
n
p
dtstore1
dtstore2
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Level 2 DFD
c
f
2.1 2.2
2.3
Origin #2
m
k
j
dtstore3
4
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Balancing
The conservation of input and output flows
through different levels
A
B
C
A
B
C
D
E
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Example of Context Diagram(Let’s check with the rules together ^^ ... Wrong? Right?)
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Example of DFD Level 1(Let’s check with the rules together ^^ ... Wrong? Right?)