A Data Flow Diagram (DFD) is a graphical representation of the flow of data within a system or process. It is a popular tool in system analysis and design to visualize how data moves through various processes, data stores, and external entities. DFDs are particularly useful for understanding and documenting the data flow in information systems. They are often used in the early stages of system development to clarify requirements and gain a better understanding of the system's data processing.
Here are some key components and symbols commonly used in a Data Flow Diagram:
Processes (Rectangles): Processes represent activities or functions that manipulate, transform, or process data. They are typically labeled with a verb-noun phrase to describe what they do.
External Entities (Rectangles with Double Lines): External entities are sources or destinations of data that interact with the system but are not part of it. They can be users, other systems, or organizations that send or receive data from the system.
Data Stores (Open Rectangles): Data stores represent where data is stored within the system. This can be a database, file system, or any other data repository.
Data Flows (Arrows): Data flows represent the movement of data between processes, data stores, and external entities. Arrows indicate the direction of data flow.
Data Stores (Open Rectangles): Data stores represent where data is stored within the system. This can be a database, file system, or any other data repository.
Data Flow Labels: Data flows are typically labeled to describe the data being transmitted. These labels help clarify what kind of data is being passed between elements in the diagram.
Data Flow Descriptions: Each data flow can have a description or additional information to provide context and details about the data being exchanged.
DFDs come in different levels of detail, from high-level context diagrams that show the system's interactions with external entities to more detailed diagrams that break down processes into sub-processes and depict finer-grained data flows.
Here's a simple example of a context-level DFD for an online shopping system:
[Customer] <--(Order)--> [Online Shopping System] --(Payment Details)--> [Payment Gateway]
In this example:
[Customer]is an external entity representing the users of the system.[Online Shopping System]is the main system or process.(Order)and(Payment Details)are data flows between the customer and the system, representing the order information and payment details being exchanged.
DFDs are valuable tools for communication between stakeholders, understanding data flow within a system, and identifying areas for system improvement or optimization. They are commonly used in combination with other modeling techniques during the system development process.
