A Data Flow Diagram (DFD) is a traditional visual representation of the information flows within a system.It shows how data enters and leaves the system, what changes the information, and where data is stored.
The DFD is also called as a data flow graph or bubble chart.
Some important points:
- All names should be unique. This makes it easier to refer to elements in the DFD.
- Remember that DFD is not a flow chart. Arrows is a flow chart that represents the order of events; arrows in DFD represents flowing data. A DFD does not involve any order of events.
Symbol used in DFD
Levels in Data flow Diagram
DFDs may be partitioned into levels that represent increasing information flow and functional detail.
Levels of DFD are as follows:
- 0-level DFD
- 1-level DFD:
- 2-level DFD:
0 Level DFD
- It is also known as fundamental system model, or context diagram represents the entire software requirement as a single bubble with input and output data denoted by incoming and outgoing arrows.
- Then the system is decomposed and described as a DFD with multiple bubbles.
- Parts of the system represented by each of these bubbles are then decomposed and documented as more and more detailed DFDs.
1 Level DFD
In 1-level DFD, a context diagram is decomposed into multiple bubbles/processes. In this level, we highlight the main objectives of the system and breakdown the high-level process of 0-level DFD into subprocesses.
2-level DFD goes one process deeper into parts of 1-level DFD. It can be used to project or record the specific/necessary detail about the system's functioning.
Other Examples
Hospital Management System
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