Data Flow Diagram (DFD)
Flow Diagram (DFD) is a graphical representation of the flow of data through an
information system. It enables you to represent the processes in your
information system from the viewpoint of data. The DFD lets you visualize how
the system operates, what the system accomplishes and how it will be
implemented, when it is refined with further specification.
diagrams are used by systems analysts to design information-processing systems
but also as a way to model whole organizations. You build a DFD at the very
beginning of your business process modeling in order to model the functions
your system has to carry out and the interaction between those functions
together with focusing on data exchanges between processes. You can associate
data with conceptual, logical, and physical data models and object-oriented
two types of DFDs, both of which support a top-down approach to systems
analysis, whereby analysts begin by developing a general understanding of the
system and gradually break components out into greater detail:
Logical data flow diagrams - are
implementation-independent and describe the system, rather than how activities
Physical data flow diagrams - are
implementation-dependent and describe the actual entities (devices, department,
people, etc.) involved in the current system.
also be grouped together to represent a sub-system of the system being
Power Designer support for DFD
Support for the Gane & Sarson and
Yourdon notations, which you choose between by selecting Tools > Model
Automatic processes and data stores
numbering (see Process and Data Store Numbering).
Data flow diagram balancing (see Data
Flow Diagram Balancing).
Data Flow Diagram specific validation
rules (F4) – Power Designer may perform automatic corrections to your model or
output errors and warnings that you will have to correct manually.