A Data Flow Diagram (DFD) is a graphical representation of the flow of data through a system. It shows the input and output data to the system, where data is stored, and how data is processed. DFDs do not show the timing or sequence of data processing. There are several elements to a DFD including processes, data stores, entities, and data flows. Processes transform input data into output data. Data stores represent where data is stored. Entities are sources or destinations of data outside the system. Data flows show the direction of data movement. DFDs can be physical or logical and have different levels of abstraction.

1. Data Flow Diagrams
(DFD)
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2. DFD
• Software design involves activities, in which transformation of
Requirement specification into abstract view of system is one of them.
• A Data Flow Diagram (DFD) is a graphical representation of the "flow" of
data through an information system.
• DFDs are also used to represent How data is Processed.
• DFD Shows
• Input Data to the system
• Output Data from the system
• Where data is stored
• DFD does not shows
• Timings of data process operations
• Sequence or parallel operations of data process
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3. Elements of Data Flow Diagrams
• Process – functions of a system to transform input data into output
data. (How data is processed)
• Represented by “circle”.
[name]
Process
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4. Elements of Data Flow Diagrams
• Data Store – Where data is stored. E.g Files, Database.
[Name]
Data Store
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5. Elements of Data Flow Diagrams
• Entity – source and destination of data to/from the system.
• Represented by “Rectangle”
• Source – Entity that supplies data to the system.
• Sink – Entity that receives data from the system.
[name]
Entity
Source Sink
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6. Elements of Data Flow Diagrams
• Data Flow – represent data flow along with direction of flow
(source/sink).
[Name]
Data Flow
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7. Types of DFD
• Physical DFD
• Graphical representation of the system showing system’s internal and
external entities and flow of data in and out of these entities
• Describes entities involved in the system
• Does not describe how processes are performed in the system
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8. Types of DFD
• Logical DFD
• Describes System and how processes are performed on data in the system
• Logical DFD represents system’s activities where are Physical DFD represents
system’s structure.
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9. Levels of DFD
• Level 0
• Highest abstraction level DFD.
• All components within the system boundary are included within a DFD
• External entities lie outside the system boundary.
• The data flow arrows to and from the external entities will indicate the
system’s relationship with its environment
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10. Thank you
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