Data Flow Diagrams (DFDs) are graphical representations of the flow of data through an information system. They enable users to visualize how data moves from input to processing and finally to output. DFDs focus on the movement of data between various processes, data stores, and external entities.
There are typically two levels of DFDs: the Context Diagram (Level 0 DFD) and Level 1 DFDs.
Context Diagram (Level 0 DFD):
This is the highest level of DFD and provides an overview of the system. It illustrates the system as a single process with its interactions with external entities. It shows the system’s boundaries, the external entities that interact with the system, and the data flowing between them. No detailed process descriptions are included at this level.
Level 1 DFD:
This level provides a more detailed view of the system’s main functions or processes. It breaks down the single process from the Context Diagram into multiple sub-processes, showing how data flows between them. It also identifies internal data stores used within the system.
DFDs use specific symbols to represent processes, data storage, data flow, and external entities. Standard symbols often include squares or rectangles for external entities, circles or rounded rectangles for processes, open-ended rectangles for data stores, and arrows to show data flow direction.
DFDs offer several benefits, including aiding in the analysis of existing systems, assisting in the design of new systems, ensuring a clear understanding of system interactions, and providing documentation that can be referred to during the system’s life cycle. They are particularly useful during the requirements analysis phase of systems development for both analysts and stakeholders.
