Types and Components of Data Flow Diagram (DFD)

Data Flow Diagrams (DFDs) are powerful visual tools representing information flow within systems. Understanding their types and components is important as each type has a different purpose, and components help in creating an accurate Data Flow Diagram (DFD).

Data Flow Diagram (DFD) is a graphical representation of data flow in any system. It is capable of illustrating incoming data flow, outgoing data flow, and stored data. Data flow diagram describes anything about how data flows through the system.

Sometimes people get confused between a data flow diagram and a flowchart. There is a major difference between a data flow diagram and a flowchart. The flowchart illustrates flow of control in program modules. Data flow diagrams illustrate the flow of data in the system at various levels. The data flow diagram does not have any control or branch elements.

There are two types of Data Flow Diagram (DFD)

1. Logical DFD
2. Physical DFD

Logical Data Flow Diagram

Logical data flow diagram mainly focuses on the system process. It illustrates how data flows in the system. In the Logical Data Flow Diagram (DFD), we focus on the high-level processes and data flow without delving into the specific implementation details. Logical DFD is used in various organizations for the smooth running of system. Like in a Banking software system, it is used to describe how data is moved from one entity to another.

When to use Logical Data Flow Diagram

Logical Data Flow Diagram are mostly used during the requirement analysis phase, user communication, and high-level system design

1. Requirement Analysis: Logical Data Flow Diagram plays a important role during Requirement analysis. It provides a clear understanding of data flow between end-user, processes and data warehouse without getting deep into technical terminology. They help in identifying what the system needs to do and how data moves within the system.
2. User Communication: Logical Data Flow Diagram is very useful communication tools between system analyst and end users. It provide a clear understanding of system requirements and functionalities to non-technical stakeholders.
3. High-Level System Design: Logical Data Flow Diagram helps in creating a high level system design for the system’s architecture . Logical Data Flow focus on processes and data flow that helps in the further development of software.

Why Logical DFDs

Logical Data Flow Diagram provide Abstraction from Technical Details, Clarity and Simplicity and excellent tools for user communication.

1. Abstraction from Technical Details: Logical Data Flow Diagram (DFD) provides a abstraction to complex model i.e. DFD hides unnecessary implementation details and show only the flow of data and processes within information system.
2. Clarity and Simplicity: Logical Data Flow Diagram provides clarity and simplicity as it uses symbols and notation for data flow, data store, processes and external entity that can be easy understand by stakeholders.
3. User Communication: Logical Data Flow Diagram is very useful communication tools between system analyst and end users.

Physical Data Flow Diagram (DFD)

Physical data flow diagram shows how the data flow is actually implemented in the system. In the Physical Data Flow Diagram (DFD), we include additional details such as data storage, data transmission, and specific technology or system components. Physical DFD is more specific and close to implementation.

When to use Logical Data Flow Diagram

Physical Data Flow Diagrams (DFDs) are used in the following situations:

1. Detailed Design Phase: Physical DFDs are helpful during the detailed design phase of a system. Logical DFD provide system processes and data flow at higher level of abstraction while physical DFD provides a more detailed view of data flow and processes within the information system.
2. Implementation Planning: Physical DFD helps developer during Implementation planning as it provides a detailed view of how data flow within the system’s physical components, such as hardware devices, databases, and software modules. Physical DFD helps the developers in identifying the correct technologies and resources required to implement the system.
3. Integration with Existing Systems: Physical DFD are important for understanding data flow when integrating a new system with existing systems or external entities,
4. Documentation and Maintenance: Physical DFDs can be referred as documentation for system architecture and data flow patterns, that helps in system maintenance and troubleshooting.

Why Physical DFDs

Physical Data Flow Diagram provides Implementation Guidance and also helps in performance optimization.

1. Implementation Guidance: Physical Data Flow Diagram provide Implementation Guidance as it provide a clear understanding of how data is flow within physical component of system. This helps the developers in identifying the correct technologies and resources required to develop and deploy the system.
2. Performance Optimization: Physical DFDs are used to optimize system performance by identifying potential bottlenecks and inefficiencies in data processing. By visualizing the physical flow of data, system architects and developers can streamline processes, reduce processing times, and improve overall system efficiency.

Following are the components of the data flow diagram that are used to represent source, destination, storage and flow of data.

• External Entity: External entity also known as Terminator, Actor, is the component of Data flow Diagram (DFD) that stands outside of the system and communicates with the system. It can be, for example, organizations like banks, groups of people like customers or different departments of the same organization, which is not a part of the model system and is an external entity. Modeled systems also communicate with terminator.
• Process: Input to output transformation in a system takes place because of process function. The symbols of a process are rectangular with rounded corners, oval, rectangle or a circle. The process is named a short sentence, in one word or a phrase to express its essence
• Data Flow: Data flow describes the information transferring between different parts of the systems. The arrow symbol is the symbol of data flow. A relatable name should be given to the flow to determine the information which is being moved. Data flow also represents material along with information that is being moved. Material shifts are modeled in systems that are not merely informative. A given flow should only transfer a single type of information. The direction of flow is represented by the arrow which can also be bi-directional.
• Warehouse (Data Store) : The data is stored in the warehouse for later use. Two horizontal lines represent the symbol of the store. The warehouse is simply not restricted to being a data file rather it can be anything like a folder with documents, an optical disc, a filing cabinet. The data warehouse can be viewed independent of its implementation. When the data flow from the warehouse it is considered as data reading and when data flows to the warehouse it is called data entry or data updating.

What symbols and notations are used to represent Components of DFD?

In Data-Flow Diagrams (DFDs), symbols and notations vary depending on the methodology being used. Here’s a summary of symbols and notations commonly associated with each methodology:

The different methodologies or approaches used for creating Data-Flow Diagrams (DFDs) are:

• Gane and Sarson
• Yourdon and De Marco
• SSADM
• UML

Each methodology provides its own set of guidelines, symbols, and notations for representing system components and their interactions.

Data Flow Diagram ( DFD) are visual maps that provides a clear understanding of how information moves within a information system. There are two types of Data Flow Diagrams (DFD) that are physical and logical DFD. Logical DFDs provides a clear understanding of system functionality and high-level data flows, that helps in requirement analysis, user communication, and high-level system design. On the other hand, Physical DFDs provide a detailed view of how data is flow and processed within the system’s physical components. Data Flow Diagram (DFD) consist of four component i.e. Processes that represent system’s functionality, External Entities that represent the end users, data store that represent database or data ware house and data flow that represent how data are flow among these three components.

What are the components of a DFD?

Four Components of DFD are:

• Process
• Data Flow
• Data Store
• External Entity

What are the features of DFD?

• DFD helps us to understand the functioning and the limits of a system.
• DFD is a graphical representation which is very easy to understand as it helps visualize contents.

What are the objectives of DFD?

The main objectives of Data Flow Diagrams (DFDs) are to visually represent how data moves through a system and to help stakeholders understand system requirements and functionalities in a clear, straightforward manner.

What is Level 3 DFD?

Level 3 DFD is the the most detailed level of DFDs, which provides a detailed view of the processes, data flows, and data stores in the system.