Dataflow Diagrams

Basic Dataflow Notation

Circles ("bubbles") labeled with actions represent functions that transform inputs into outputs.
Data Flows
Directed arrows labeled with data type represent data moving through the system
Data Stores
Bars (also boxes and ellipses) labeled with data type represent data or aggregates of data that must be remembered for a period of time (typically implemented as files or database)
Boxes represent external entities (source/sink) with which the system communicates (e.g., individuals, groups, external computer systems)

A Typical Dataflow Diagram

Figure 4.2

Levels in a Set of Diagrams

The Context Diagram
Diagram/Figure 0
Subdiagrams / Process Descriptions
Data Dictionary

Leveled Dataflow Diagram

Figure 9.21

Rules for Drawing Dataflow Diagrams

Drawing Diagrams

Naming in Diagrams

Strategies for Drawing Dataflow Diagrams

The process may be unstructured, tedious, and iterative, but the result must be well-organized.

Evaluation and Refinement of a System Description

Evaluation Criteria


A Complex Dataflow Diagram

Figure 9.20

Refinement of Dataflow Diagrams

Independence of Transformations
Aggregation of Related Transformations

From Perlman, Ohio State University, 1996