Data Flow Diagram (DFD) Overview

Data Flow Diagram (DFD)

• A visual representation of information flow within a system.

DFD Symbols

• Four basic symbols used to represent a DFD:

Process

• Receives input data and produces output with a different content or form.
• Can be simple (e.g., collecting input data and saving it in the database).
• Can be complex (e.g., producing a report containing monthly sales).
• Every process has a unique name identifying the function it performs.
• Process name consists of a verb followed by a singular noun.
• Examples: Apply Payment, Calculate Commission, Verify Order.
• At least one data-flow must enter and one data-flow must exit each process symbol.

External Entity

• A person, department, outside organization, or other information system.
• Provides data to the system or receives outputs from the system.
• Represented by a rectangle.
• Supplies or receives data, but does not process data.
• Components outside of the boundaries of the information system.
• Interacts with the outside world.