Data Flow Diagram Symbols

In this guide, you will learn what a data flow diagram is and explore standard symbols and notation. For those looking to create a data flow diagram, an intuitive diagramming tool can help you achieve professional results quickly, offering multiple editable DFD templates. Discover how easy it can be!

Businesses consist of numerous moving parts and departments, making it challenging to track each aspect of their contributions. Continuously identifying processes or areas for improvement enhances business efficiency and productivity. Data flow diagrams (DFD) are among the most straightforward yet effective tools for businesses to understand, refine, and implement new systems. DFD symbols provide visual representations of an organization's processes or systems, making them easy to comprehend and optimize.

The data flow diagram offers insights into the process itself, the inputs and outputs of each entity, and the various subprocesses through which data moves. Visualizing each element within the process makes it easy to identify inefficiencies and develop optimal systems.

Data flow diagrams originated from their use in operational research to model organizational workflows. DFDs evolved from the Activity Diagram used in Structured Analysis and Design Technique (SADT) in the late 1970s. They quickly gained popularity as a way to visualize process data and steps. Although initially used to illustrate data flow in computer systems, DFDs soon became valuable for documenting significant data flows across various domains.

Learn how to create a data flow diagram with an intuitive tool through our step-by-step video tutorial. Watch now!

Before creating a data flow diagram, it's essential to determine whether a physical or logical DFD best suits your needs.

Physical DFD focuses on how processes occur by specifying the files, software, hardware, and people involved in an information flow.

Logical DFD focuses on the information being transmitted, the entities receiving it, and the general processes that occur. It describes business activities without delving into technical details.

Using both physical and logical data flow diagrams to describe the same information flow can provide more comprehensive details than each could independently.

Data Flow Diagram Symbols

DFD symbols are standardized notations that depict a system or process. They utilize short-text labels, arrows, circles, and rectangles to illustrate data flow direction. DFDs also include various sub-processes, data storage points, and data inputs and outputs.

A data flow diagram consists of four fundamental elements: external entities, data stores, processes, and data flows. These elements are best represented using the two primary notation methodologies: Yourdon & Coad and Gane & Sarson. While DFD symbols vary slightly between methodologies, the core concepts remain consistent.

Data Flow Diagram

Data Flow Model Diagram

Yourdon and Coad

Download Data Flow Diagram Symbol Legend

Data Flow Diagram Notations

External Entity - An external process or system that sends or receives data to and from the diagrammed system. Also known as sources, terminators, sinks, or actors, represented by squares.

Process - A procedure that manipulates data by processing incoming data into an output. Processes (typically involving input-processing-output) are depicted by rectangles with rounded corners, containing three descriptive elements:

First, an identification number appears in the upper left corner, assigned arbitrarily at the top level as a unique identifier.

Second, a location description to the right of the identifier specifies where the process occurs within the system (e.g., a department or hardware component). Finally, a descriptive title is centered in the box, typically a simple imperative sentence with a specific verb, such as 'maintain customer records' or 'locate driver.'

Data Store - A repository for information within the system, represented by an open-ended narrow rectangle. Data stores can be long-term files like sales ledgers or short-term accumulations, such as batches of documents awaiting processing. Each data store should have a reference followed by an arbitrary number.

Data Flow - Illustrates the movement of information from its source to its destination, represented by a line with arrowheads indicating direction. Information always flows to or from a process and can be written, verbal, or electronic. Each data flow can be referenced by the processes or data stores at its head and tail, or by a description of its contents.

Resource Flow - Depicts the flow of physical materials from their source to their destination, sometimes referred to as physical flows.

The physical material should be clearly labeled. Resource flows are usually included in early, high-level diagrams when describing the physical movement of materials is crucial for analysis.

To create a valid DFD, follow these four essential guidelines. They provide the best framework for creating effective data flow diagrams.

With this background knowledge and the fundamental rules, you can build your own DFD. The process involves these five steps:

1. Identify major inputs and outputs in your system

This step provides a macro view of your system and clarifies the primary tasks it should accomplish. These elements form the foundation of your DFD.

2. Develop a context diagram (Level 0 DFD)

Create a single process node and connect it to relevant external entities. This node represents the general process information undergoes from input to output within the system.

3. Expand the context diagram into a Level 1 DFD

Level 1 DFDs provide a more detailed overview than context diagrams. Break down the single process into specific subprocesses to illustrate where information originates and what transformations it undergoes.

4. Expand to Level 2+ DFD

Further decompose processes into more detailed subprocesses. Include any necessary data stores and flows at this stage.

5. Verify the accuracy of your final DFD

Review your diagram carefully, focusing on information flow. Ensure it is logical, includes all necessary data stores, and is comprehensible to other stakeholders.

See how these symbols are applied in practical data flow diagrams. Create clear and effective DFDs with EdrawMax!

1. Sales Data Flow Template

2. Warehouse Data Flow Diagram Template

3. Train Tickets Reservation DFD

Businesses rely on systems and processes for efficient operation. How team members interact with these systems significantly impacts overall efficiency.

Data flow diagrams provide essential insights into a system's inputs, outputs, and processes, offering valuable information for analysis and improvement. Whether optimizing existing processes or implementing new ones, a DFD simplifies your task. Download relevant templates from EdrawMax and create your own professional DFDs.

Related Resources

How to Create a Data Flow Diagram

DFD Examples

Data Flow Diagram

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