graph TD
A[Functionality of a System] --> B[Hierarchy of Data Flow Diagrams]
B --> C[Data Flow]
B --> D[Persistent Data]
E[Data Dictionary] --> C
E --> D
F[Context Diagram] --> G[Sources of Incoming Data Flows]
F --> H[Destinations of Outgoing Data Flows]
style A fill:#f9d2de,stroke:#f17c91,stroke-width:2px;
style B fill:#eaf9d4,stroke:#85c467,stroke-width:2px;
style E fill:#fceee3,stroke:#fcb6b2,stroke-width:2px;
style F fill:#d0f0fd,stroke:#71c0e2,stroke-width:2px;
An approach for specifying the Functionality of a system based on a hierarchy of Data Flow Diagrams. Data flows as well as persistent data are defined in a data dictionary. A Context Diagram models the sources of incoming and the destinations of outgoing Data Flows.
