IE Analysis: Data flow diagram |
Data
flow diagram (DFD):
A graphic model of the flow, and transformation of data through a set of processes..
DeMarco(1978), Gane and Sarson(1979) and Yourden suggest that the data flow diagram should be the first tool used by the systems analyst.
Symbols: |
The following symbols are commonly used in these methodologies;
External Entity |
An object representing the source or destination of data outside the system | |
Process |
An object representing a modification of data within a system | |
Data Flow |
A line showing the movement of data between two objects. | |
Data store |
An object representing a repository of data. | |
Import connector |
An object representing an external entity or data store defined in an upper level. | |
Duplicates |
If more than one occurrence of an object are required on a
diagram; Gane & Sarson follows the conventions at left. Note: the bar does not indicate the actual number of duplicates of that object. |
[Rev 13/6/97] © 1997 V/2-Com (Verhaart), P O Box 8415, Havelock North, New Zealand.
