Home >> Data Flow Diagrams

Contents

• Purpose
• Symbols
• Advantages
• Disadvantages
• Rules
• Example
  • Diagram 1
  • Diagram 2

Purpose:

To capture the processes of a system in a top/down manner.

Symbol	Description
	Process
	External
	Data File
	Flow of Data

1. Various levels of detail aid in communication with different interest groups.
2. The top/down approach often secures management endorsement.

1. Capabilities are lost between diagrams
2. Systemic myth and rhetoric are easily captured and stored

1. Processes must have input and output.
2. All symbols must have unique labels.
3. Data must flow in only one direction.
4. No recursion.
5. Processes and External Entities must be numbered.
6. There must be a process between:
   • files
   • external entities
   • file and external entities
7. Data flows must remain the same to all destinations
8. Joined data flows must be equal.

Diagram 1: The Context Diagram

Diagram 2