[Level 1 Data Flow Diagram -] this highlights the main functions carried out by the system. As a rule, we try to describe the system using between two and seven functions. SQA
What is a data flow diagram (DFD)?
Data flow diagrams or DFDs help the analysis of systems by showing:
Data sources
What processing happens and by whom
Who uses the data
Where data is stored and when
Outputs produced
Representing the complete business system often requires multiple levels of diagram.
The top level, is referred to Level 0 or the Context Diagram, it represents the system as one process box. Level 1 data flow diagrams show incoming data flow, processes and output data flows.
Level 1 DFDs should show a process to handle each incoming data flow and a process to generate each output data flow.
Example Data Flow Diagrams
This example of a level 1 data flow diagrams is free to copy, download and use.