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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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