Discuss in details about Functional Modeling.

• This model describes the computations that take part within a system.
• This model is helpful when the conversion from the inputs to outputs is complex.
• The functional model of a system can be shown by a data Flow Diagram (DFD).

Data Flow Diagrams/Data Flow Graph/Bubble chart

• A DFD is a graphical diagram that depicts the information flow and the change that are applied when the data shift from input to output.
• Level 0 DFD also known as fundamental system model or context model which describes the total software act as a single bubble with input and output data indicated by incoming and outgoing arrows.
• Level 1 DFD contains 5 or 6 bubbles. Every bubble can be refined at Layers to depict more details.

Extensions to Real Time Systems

• Ward and Meller extensions
• Hatley and Pirbhai extension.