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Data Flow Diagrams (DFD)

Data Flow Diagrams - DFD (also called data flow graphs) are commonly used during problem analysis. Data Flow Diagrams (DFDs) are quite general and are not limited to problem analysis for software requirements specification. They were in use long before the software engineering decipline begin. DFDs are very useful in understanding a system and can be effectively used during analysis.

A DFD shows the flow of data through a system. It views a system as a function that transforms the inputs into desired outputs. Any complex system will not perform this transformation in a "single step", and a data will typically undergo a series of transformations before it becomes the output. The DFD aims to capture the transformations that take place within a system to the input data so that eventually the output data is produced. The agent that performs the transformation of data from one state to another is called a process (or a bubble). So a DFD shows the movement of data through the different transformation or process in the system.

DFDs are basically of 2 types: Physical and logical ones. Physical DFDs are used in the analysis phase to study the functioning of the current system. Logical DFDs are used in the design phase for depicting the flow of data in proposed system.

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