Data Flow Diagrams: Understanding DFD Symbols
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Data Flow Diagrams
1
What is a Data Flow Diagram?
A data flow diagram (DFD) is a
graphical representation of the
movement of data between external
entities, processes and data stores within
a system.
Simply put, DFD’s show how data
moves through an information system.
2
DFD Symbols
3
Process
The work or actions performed on data so that they
are transformed, stored, or distributed.
Process labels should be
verb phrases!
4
A path for data to move from one part of the
system to another.
Data in motion!
Arrows depict the movement of data.
NO VERBS
5
Data Flow
Data Store
Used in a DFD to represent data that the system
stores
Data at rest!
Labels should be noun phrases
(NO VERBS)
6
External Entity aka Source/Sink
The origin or destination of data!
This represents things outside of the system.
Source – Entity that supplies data to the system.
Sink – Entity that receives data from the system.
The labels should be noun phrases!
7
General DFD Rules
8
Y
E
S
N
O
Advantages of DFDs
Simple graphical techniques which are
easy to understand
Helps define the boundaries of the
system
Useful for communicating current
system knowledge to users
Explains the logic behind the data flow
within the system
Used as the part of system
documentation file
Rottman makes you do these in design!
9
Group Exercise
Get into your project groups and figure
out the best solution for the level 0 DFD
for the National Merchandising Case!
When you are done have one team
member come and put your solution on
the board.
10
A data flow diagram (DFD) is a visual representation of data movement within a system, depicting the flow of data between entities, processes, and data stores. This content explains DFD symbols, process representation, data flow paths, and more. Learn how DFDs help in system analysis, documentation, and communication of data flow logic.
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Presentation Transcript
What is a Data Flow Diagram? A data flow diagram (DFD) is a graphical representation of the movement of data between external entities, processes and data stores within a system. Simply put, DFD s show how data moves through an information system. 2
Process 1.0 Grade Report Grade Detail Produce Grade Report The work or actions performed on data so that they are transformed, stored, or distributed. Process labels should be verb phrases! 4
Data Flow 2.1 Payment Detail Accounts Receivable D1 Post Payment Invoice Detail A path for data to move from one part of the system to another. Data in motion! Arrows depict the movement of data. NO VERBS 5
Data Store D1 Students Used in a DFD to represent data that the system stores Data at rest! Labels should be noun phrases (NO VERBS) 6
External Entity aka Source/Sink 1.0 Order Invoice CUSTOMER Verify Order The origin or destination of data! This represents things outside of the system. Source Entity that supplies data to the system. Sink Entity that receives data from the system. The labels should be noun phrases! 7
General DFD Rules YES NO A process to another process A process to an external entity A process to a data store An external entity to another external entity An external entity to a data store A data store to another data store 8
Advantages of DFDs Simple graphical techniques which are easy to understand Helps define the boundaries of the system Useful for communicating current system knowledge to users Explains the logic behind the data flow within the system Used as the part of system documentation file Rottman makes you do these in design! 9
Group Exercise Get into your project groups and figure out the best solution for the level 0 DFD for the National Merchandising Case! When you are done have one team member come and put your solution on the board. 10
