Difference Between Physical DFD and Logical DFD

To understand the differences between a physical and logical DFD, we need to know what DFD is. A DFD stands for data flow diagram and it helps in representing graphically the flow of data in an organization, particularly its information system. A DFD enables a user to know where information comes in, where it goes inside the organization and how it finally leaves the organization. DFD does give information about whether the processing of information takes place sequentially or if it is processed in a parallel fashion. There are two types of DFD’s known as physical and logical DFD. Though both serve the same purpose of representing data flow, there are some differences between the two that will be discussed in this article.

Any DFD begins with an overview DFD that describes in a nutshell the system to be designed. A logical data flow diagram, as the name indicates concentrates on the business and tells about the events that take place in a business and the data generated from each such event. A physical DFD, on the other hand is more concerned with how the flow of information is to be represented. It is a usual practice to use DFD’s for representation of logical data flow and processing of data. However, it is prudent to evolve a logical DFD after first developing a physical DFD that reflects all the persons in the organization performing various operations and how data flows between all these persons.

What is the difference between Physical DFD and Logical DFD?

While there is no restraint on the developer to depict how the system is constructed in the case of logical DFD, it is necessary to show how the system has been constructed. There are certain features of logical DFD that make it popular among organizations. A logical DFD makes it easier to communicate for the employees of an organization, leads to more stable systems, allows for better understanding of the system by analysts, is flexible and easy to maintain, and allows the user to remove redundancies easily. On the other hand, a physical DFD is clear on division between manual and automated processes, gives detailed description of processes, identifies temporary data stores, and adds more controls to make the system more efficient and simple.