What are the four elements of a Data Flow Diagram (DFD)?

Question

Accepted Answer

Process (circle), Data Store (parallel lines), Source/Sink (rectangle), and Data Flow (labelled arrow).

* Standard DFD notation: process, data store, external entity (source/sink), and data flow. — wooptoo, Public domain, via Wikimedia Commons. *
DFD Element Notation:

Element
Symbol
Description

Process
Circle/Oval
Transforms data (e.g., "Calculate route")

Data Store
Open rectangle/parallel lines
Stores data (e.g., "Route data")

Source/Sink
Rectangle
External entity (e.g., "GPS satellite system", "Driver")

Data Flow
Arrow with label
Shows data movement direction

Example from Navigation System:

External entities: GPS satellite system, Driver, Traffic information server
Processes: Calculate route, Determine next waypoint, Recalculate route
Data stores: Route data
Data flows: Location data, Destination, Traffic information, Current route

Go deeper:

Data-flow diagram (Wikipedia) — the four symbols and the rules (no store-to-store flow, 3–9 processes per diagram).

Element	Symbol	Description
Process	Circle/Oval	Transforms data (e.g., "Calculate route")
Data Store	Open rectangle/parallel lines	Stores data (e.g., "Route data")
Source/Sink	Rectangle	External entity (e.g., "GPS satellite system", "Driver")
Data Flow	Arrow with label	Shows data movement direction