Presenting Using Different Forms of Notation

Presenting a Data Flow Diagram (DFD)

A DFD shows how data moves through a system. It focuses on where data comes from, what process uses it, where it is stored, and where it goes next. It is about the movement of data — not the logic of decisions.

Step 1: Identify the DFD parts

Read the scenario once and sort what you find into four lists:

• External entities — people or systems outside the boundary that send or receive data
• Processes — steps that transform or use data
• Data stores — databases or files where data is held
• Data flows — the data that moves between components, named precisely

No drawing yet.

Step 2: Build the Skeleton

Place the components on the page without arrows:

• External entities sit on the far left and right, outside the system boundary
• Processes sit in the middle, roughly in the order they happen
• Data stores sit close to the process that uses them

Planning the layout first prevents the diagram from becoming cluttered once arrows are added.

Step 3: Add Labelled Arrows

Connect the components by following the scenario in order:

• Draw an arrow each time data is sent, stored, or returned
• Label each arrow with the name of the data — not a vague action word
• Keep the general flow as entity → process → data store → process → entity, avoiding direct links between an entity and a data store