What is the full form of DFD?

Introduction

Data Flow Diagram (DFD) is a perspective model of the flow of data through the process by which the user can understand it easily.

By this DFD the system is represented graphically and aimed to reach the concept for both computer specialists and non-specialists in the same way. During specification and analysis of the requirements, DFD helps software engineers, users, and customers to work together.

What is DFD?

The full form of DFD is Data Flow Diagram. It was made popular by Larry Constantine and Edward Yourdon in the late 1970s. The computational base model “Data Flow Graph” given by David Martin and Gerald Estrin is the basis for DFD. The system’s data flow is represented by DFD in a graphical manner. In this, a limited set of constructs is used and the designing rules are simple and easier to follow. This methodology was raised by a few, such as Tom DeMarco, Trish Sarson, and Chris Gane. All of them worked together and defined symbols and notations for DFD.

It may be logical or physical. Logical DFDs show information such as system processes and activities and do not provide information on technology. They are used by line organisations and enterprise architects. Physical DFD provides more information physically and it is used by the development team.

Elements of DFD

The four basic elements of DFD are process, data flow, data storage or warehouse, and the external entity or terminator.

Process

The process function is responsible for the input and output transformation in the system. The symbols used in the process are mostly circles, rectangles, ovals, or rectangles with their corners rounded. The essence of the process is clearly given by a single word or phrase or sentence.

Data flow

The data information that is transferred from one part of the system to the other is described by the data flow. The symbol used for data flow is an arrow symbol. It shows the direction of data flow and it shows both directions. It also represents the materials with their information to be moved.

A data store or Warehouse

Warehouses are used to store the data for later use. The symbol that is used to represent the data store is the symbol of two horizontal lines. It is not only like a data file but also a filing cabinet, document folder, and optical disc. The data that flow from the data store is given as data reading and the data that flows into the data store is denoted as data updating or data entry.

The external entity or terminator

The external entity that stands outside the system and has communication with it is known as a terminator. It may be a business system or a computer system which is a source and destination of information. It is probably at the edge of the diagram.

Levels of DFD

There may be many levels in DFD according to the scope of the work. But generally, it is categorised as levels 0, 1, 2, and 3.

Level 0

Zero level is the basic outline of the entire system. It is also called a context diagram and it gives the overall picture of the system. This level is the highest and should be easy to understand by all. It is the top view of the system.

Level 1

The main function of the system and the interactions between them are represented by level 1. It is the broad view of the system which includes more details and sub-processes.

Level 2

Level 2 is a much deeper step than Level 1. If there is a need for more information on the system's functioning, then this level is used.

Level 3

Level 3 and beyond level 3 are needed only when the system is complicated. These levels are not used commonly.

Uses of DFD

• The technical development team on the software side uses DFD to understand the approach.

• DFD is used by business analysts for analysis of existing systems and their inefficiencies.

• As it is easy to understand it is used for the analysis of any system and its progress.

Conclusion

DFD is known as the data flow diagram. It is represented by using many symbols and notations to easily understand the data flow through the system. There are four elements such as data in and out, data storage, and process. This is carried over in different levels using symbols. DFD makes the possibility of understanding the system by both technical and non-technical persons.

FAQs

Q1. What are the rules that are used for the creation of DFD?

• The entity names should be in a comfortable and easy manner. The flow of the process should be in order.

• There may be many processes in a single DFD. The limit may be between three to nine.

• The data should not flow between two entities or two stores.

Q2. What are the symbols that are used in DFD?

DFD symbols vary according to the methodology. The methodology was named after the creators such as Gane and Sarson, Yourdon and Coad, and Yourdon and DeMarco. There are slight changes in the usage of symbols like circle rectangle etc. Circle was used for denoting the processes in DFD by both Yourdon and Coad and Yourdon and DeMarco methods. But in Gane and Sarson's methodology, it was denoted by a rectangle with its corners rounded.

Q3. What are the steps involved in creating a Data Flow Diagram?

The creation of DFD is divided into five steps.

• The system’s input and output identification

• Simply building a context diagram

• Expansion of context diagram into level 1 DFD

• Expansion to level 2 of DFD

• Final diagram’s accuracy confirmation