Introduction to DFDs
Preparing a DFD is more of an art than a science. This series of exercises provides one set of guidelines for creating a top level logical DFD which will provide a general overview of the information processing that takes place within a system. These exercises do not address how top level DFDs can be decomposed into a series of more detailed, lower level DFDs.
A DFD is comprised of four components namely:
- entities (represented by
), - files (represented by
), - processes (represented by
) where X.0 is a number, - data flows (represented by arrows).
Note that
- there is no one set of unchanging rules for creating DFDs
- there can be a number of equally acceptable DFDs for a system.
- There are a number of different symbol sets in use.