A structural analysis method

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Levels of DFD

Level 0 - Highest abstraction level DFD is known as Level 0 DFD, which depicts the entire

information system as one diagram concealing all the underlying details. Level 0 DFDs are

also known as context level DFDs.



Level 1 - The Level 0 DFD is broken down into more specific, Level 1 DFD. Level 1 DFD

depicts basic modules in the system and flow of data among various modules. Level 1 DFD

also mentions basic processes and sources of information.

Issue item


Finance verification

Customer data





Level 2 - At this level, DFD shows how data flows inside the modules mentioned in Level 1.

Higher level DFDs can be transformed into more specific lower level DFDs with deeper level

of understanding unless the desired level of specification is achieved.


The Waterfall Model was first Process Model to be introduced. It is also referred to as a linear sequential life cycle model. It is very simple to understand and use. In a waterfall model, each phase must be completed before the next phase can begin and there is no overlapping in the phases.

Following is a diagrammatic representation of different phases of waterfall model.

The sequential phases in Waterfall model are:

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