What is a Data Flow Diagram (DFD)

DFD, which stands for Data Flow Diagram, provides a visual representation for the flow of data across a system. Ideally, there are three major components in a DFD – entity, database, and process. An input or output unit can be defined as an entity and processes establish a relationship between entities/database units. Ideally, a data flow diagram acts as a flowchart for business processes and information systems. Since it has such a wide range of application, it is commonly used in numerous sectors these days. Let’s get to know what is a Data Flow Diagram and how to create it in this informative guide.

What is a Data Flow Diagram?

As the name suggests, a Data Flow Diagram represents how data is passed through a system. To do this, it provides information about the input, output, and the processes related to the system. In simple words, it depicts the flow between different entities in a system and how data is processed. Mostly, it looks like a flowchart and helps us work on database management and system analysis.

What is Data Flow Diagram

History of Data Flow Diagram

Before we get to know what a Data Flow Diagram is, let us quickly discuss its history. The concept was originally derived from graph theory and gained popularity in the 1970s when Ed Yourdon and Larry Constantine released their Structured Design book. Though, it was David Martin and Gerald Estrin that coined these graphs as “data flow models” with their academic research.

Gradually, the concept was linked with Object-oriented Analysis and Design as it makes it easier for developers to visualize their system’s data flow. As of now, it is considered as a part of structured analysis modeling and is closely related to UML’s activity diagram.

Applications of DFD

Since DFDs are so easy to make and have a universal appeal, they are used in numerous ways. Following are some of the major applications of Data Flow Diagrams.

Database designing

With the help of a complete Data Flow Diagram, we can come up with the overall design of the database. Ideally, a DFD is drawn before database creation as it provides the conceptual and physical structure of the database that can later be used.

System analysis

Apart from designing the database, DFD can help us understand how the overall system works. By examining the flow of data from one entity to another, we can further analyze the working of the system and its input/output entities.

Decision making

Engineers need to make tons of decisions during the creation, implementation, and deployment stages of the database. A DFD can help us make better decisions by providing an overall visual representation of the system.

Error detection

In case if there is an issue with your system, then you can scan the DFD. This will help you detect any error and even resolve it in the long run.

Other applications

There are numerous other organizational and management applications of a DFD. This is why they are so extensively used in business processing and management sectors.

The Advantages and Limitations of DFD

Now when you know what a Data Flow Diagram is, let’s dive into its details. If you want to make DFDs regularly, then you should be aware of their advantages and limitations as well.

Advantages of DFD
  • Data flow diagrams are pretty simple and considered easy to make. No thorough training is needed to work on them.
  • They are extremely diverse and can be used to depict the flow of data in almost every possible system.
  • Apart from databases, DFD can also be used to depict input and output entities. This helps us draw comparisons with the real-world entities.
  • There are all kinds of levels and structures in DFD. This can help us get an extensive representation of the system.
  • It provides a precise and clear representation of the data flow, without involving any unwanted entities.
  • It lets us understand the logic and concept behind the system and helps with its organizational management.
Limitations of DFD
  • It does not provide a complete picture of the system and leaves some vital physical entities.
  • Sometimes, a DFD can be confusing and programmers might not differentiate between its levels.
  • At times, it can be tough to conceptualize an object-oriented structure in a hierarchical format.

Data Flow Diagram Symbols and Rules

One of the best things about Data Flow Diagrams is that they are extremely easy to make. To start with, you need to consider the following symbols to represent entities and the flow of data.

Process:This represents any task that is performed by the system on the input data. It results in a processed output of data. A process can be related to the modification, storing, deletion, creation, or any other operation on data. It is represented by a circle or a round-edged rectangle.

DFD Process Symbol

Database:This is where data is stored in a system. It can also be the input or output of a process as well. It is represented by a rectangle, which can sometimes have a small section for its ID.

DFD Database Symbol

Entities:They are either the source or the termination of the DFD. Ideally, they represent an external source from where data is taken or processed in the end. Entities are represented by a closed square/rectangle.

DFD Entities Symbol

Data Flow:Lastly, we use directional arrows to represent the flow of data from one entity/database to another. The line would have a directional arrow in the end to depict the source and the destination units.

DFD Data Flow Symbol

Apart from the Data Flow Diagram symbols, also consider the following common rules in mind:

  • A DFD has to be complete and includes all the vital components of the system.
  • It should be consistent in nature. That is, if you are working on one level, it should only be nested with another level.
  • There should be no direct link between one entity/database to another entity/database. A process should be present in the middle of entity-database, database-database, and database-entity connection.
  • Each component in the system should have at least one data flow linked to it.
  • There should be one specific source and an output unit in a DFD.

DFD Levels and Layers

A Data Flow Diagram can be created at different levels and layers. Before you work on a DFD on your own, it is important to know how extensive it can be used.

Physical vs Logical Layer

A logical diagram provides an overview of the business activities in a system. It doesn’t focus on how the data is stored rather it lets us know how it is implemented. It provides business controls and the flow of data from a user perspective.

Logical Data Flow Diagram

On the other hand, a physical layer provides a more low-level representation of how the data is stored. It consists of databases and physical entities that are needed in a system. There are all kinds of manual processes and core data-driven decisions that we can make out at a physical level.

Physical Data Flow Diagram
Different levels of Data Flow Diagrams

Apart from their physical and logical layers, a DFD can also be distinguished on the basis of several levels.

Level 0:This is the highest level of the DFD that simply provides the overall representation of the system at a glass. It is also known as a context diagram.

Highest Level of Data Flow Diagram

Level 1:This is a more detailed version of the previous level that includes database and different vital entities.

Level 1 of Data Flow Diagram

Level 2 and beyond:As we dig deeper into the system and provide a more detailed visual representation of it, the DFD’s level would automatically keep increasing.

Level 2 of Data Flow Diagram

Classical Examples of DFD

To further understand what a Data Flow Diagram is, let’s further discuss the following examples.

Ticket Booking

This Data Flow Diagram has been inspired by the real-world activity of booking flight tickets. Either passengers or agents can log-in to the system, verify their information, and book tickets. It also includes accounting and ticket processing entities.

Ticket Booking Data Flow Diagram
ATM Withdrawal

Another simple DFD that you can see is related to money withdrawal from the ATM. Once the action is verified, users can withdraw money and check the balance of their account. It also prints the receipts and updates the balance.

ATM Withdrawal Data Flow Diagram
Online Shopping

This is a more complex DFD that depicts the entire flow of online shopping. Once the orders are made, the products are shipped from the warehouse to the customer. The funds are transferred, invoices are generated, and the warehouse is updated.

Online Shopping Data Flow Diagram

How to Create a Data Flow Diagram with EdrawMax?

To create all sorts of Data Flow Diagrams, you can consider following this stepwise process.

Step 1: Pick the DFD level

Firstly, you need to identify how you are going to represent the system. Just pick between the physical or logical layers and the level at which you will represent the process.

Step 2: Identify key entities and processes

A Data Flow Diagram is all about key entities and the processes connecting them. Therefore, you need to identify the input and output sources of the system and how they would be processed.

Step 3: Use EdrawMax to make a DFD

Once you have everything ready, you can take the assistance of a dedicated tool like EdrawMax. It has readily available templates for DFD that you can choose to save your time and efforts.

A canvas would be loaded in the center while you can view different vectors and options on each side. Simply drag a vector from the sidebar and drop it to your canvas. There are readily available vectors for entities, processes, data flows, etc.

Without any prior designing experience, you can easily customize them. Double click the vector to add your own text, draw connections between different entities, and change the overall appearance of the diagram. In the end, you can simply export it in the format of your choice.

Who knew it would be so easy to work on Data Flow Diagrams, right? With the help of a professional tool like EdrawMax, you can come up with lots of useful DFDs in no time. It has a friendly interface and has included several templates to pick from. Also, with its numerous editing features, you can draft a customized DFD on any topic. There is no prior designing experience needed to work on EdrawMax. The best part is that it offers a free trial version as well. So what are you waiting for? Go ahead and try this remarkable tool for free and be the judge of it yourself!

Related Articles

download EdrawMax EdrawMax online
main page