Explain Data flow design

The data flow model is a set of “policies and diagrams representing the design requirements" that you need to implement in order to meet the goals in your solution proposal. Data flow model policies are simple statements of the business requirements found in your solution proposal. You refine each statement so that it evolves into a precise policy of your business requirements.

Data-flow-design is concerned with designing a sequence of functional transformations that convert system inputs into the required. The design is represented as data flow diagrams. A data flow diagram (DFD) is a graphical representation of the "flow" of data through an information system, modelling its process aspects. Often they are a preliminary step used to create an overview of the system which can later be elaborated. DFDs can also be used for the visualization of data processing (structured design).

A DFD shows what kinds of information will be input to and output from the system, where the data will come from and go to, and where the data will be stored. It does not show information about the timing of processes, or information about whether processes will operate in sequence or in parallel.