The main difference between Logical DFD and Physical DFD is that Logical DFD focuses on business and related activities while Physical DFD focuses on how the system is implemented.
Data Flow Diagram (DFD) explains the flow of data of an information system. There are two types as Logical DFD and Physical DFD. Logical DFD provides an insight into what the system is while Physical DFD defines the implementation of the system. Both these diagrams help to represent the system, understand it and to improve it further.
Key Areas Covered
1. What is DFD
– Definition, Functionality
2. What is Logical DFD
– Definition, Functionality
3. What is Physical DFD
– Definition, Functionality
4. Difference Between Logical DFD and Physical DFD
– Comparison of Key Differences
Key Terms
Data Flow Diagram (DFD), Logical DFD, Physical DFD
What is DFD
DFD is a graphical representation of how data flows from one component to another in an information system. It does not cover details by going in depth. Instead, it provides only an overview of the system. DFD has symbols for processes, data stores, data flow, and external entities.
A DFD has the following features.
- A process should have at least one input and output.
- Stored data should go through a process.
- One process can go to another process of a data store.
- Also, a data store must have at least one data flow in and one data flow out.
Overall, DFD is used in various fields such as Software Engineering, Business Analytics, Re-Engineering, Structured Analysis, etc.
What is Logical DFD
Logical DFD focusses on business and business activities. It is the basis for the physical DFD. Furthermore, it describes the business events and data necessary for those events. Also, it provides a solid basis for physical DFD, which depicts how the data system will work; for example, hardware, software, paper files, and people involved.
Logical DFD allows mapping the flow of business actions as it is. It helps to emphasize the shortcomings and inefficiencies. Also, it helps to identify the process steps in order to eliminate or modify them. Besides, it is also easier for non-technical people to understand logical DFD. Therefore, it is a common diagram in business activities. Moreover, it provides information about the functionality without implementations.
Furthermore, Logical DFD allows getting a thorough understanding of the system. It also helps to identify mistakes and shortcomings. Moreover, logical DFD is an essential diagram as it helps to minimize the associated risks. It elaborates the data flow to create better functionalities regardless of the technical solutions or how the system is going to implement.
What is Physical DFD
The next diagram to draw after creating a logical DFD is physical DFD. It explains the best method to implement the business activities of the system. Moreover, it involves the physical implementation of devices and files required for the business processes. In other words, physical DFD contains the implantation related details such as hardware, people and other external components required to run the business processes.
Difference Between Logical DFD and Physical DFD
Definition
Logical DFD is a type of DFD that depicts how the business operates while physical DFD is a type of DFD that depicts how the system is implemented.
Main Focus
Thus, while logical DFD focuses on business activities, physical DFD focuses on system implementation. Hence, this is the main difference between Logical DFD and Physical DFD.
Processes
In a Logical DFD, a process is a business activity. However, in Physical DFD, a process is a software program or manual procedures.
Data stores
Data stores are another difference between Logical DFD and Physical DFD. In a Logical DFD, a data store is a collection of information, which explains how the data is stored. However, in a Physical DFD, data stores are databases, computer files and paper files.
Complexity
Even a non-technical person can understand Logical DFD as it is simpler than Physical DFD. But, physical DFD is more complex.
Conclusion
DFD is a representation of a data flow of a process or a system. There are two types of DFD as Logical DFD and Physical DFD. The main difference between Logical DFD and Physical DFD is that logical DFD focuses on business and related activities while Physical DFD focuses on how the system is implemented. In brief, Logical DFD is the basis for Physical DFD.
References:
1.“Data-Flow Diagram.” Wikipedia, Wikimedia Foundation, 8 Mar. 2019, Available here.
2.“Logical vs. Physical Data Flow Diagram.” Lucidchart, Available here.
Image Courtesy:
1. “Data Flow Diagram Example” By John Azzolini – Introduction to Systems Engineering Practices, Public Domain via Commons Wikimedia
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