Data Flow Diagram - Types of DFD


Physical and Logical DFDs

There are two types of data flow diagrams, namely physical data flow diagrams and logical data flow diagrams and it is important to distinguish clearly between the two:

Physical Data Flow Diagrams

An implementation-dependent view of the current system, showing what tasks are carried out and how they are performed. Physical characteristics can include:

Names of people
Form and document names or numbers
Names of departments
Master and transaction files
Equipment and devices used
Locations
Names of procedures

Logical Data Flow Diagrams

 

An implementation-independent view of the a system, focusing on the flow of data between processes without regard for the specific devices, storage locations or people in the system. The physical characteristics listed above for physical data flow diagrams will not be specified.

Comments

Post a Comment

Popular posts from this blog

Food Ordering System

Image
Food Ordering System 0 (Zero) level DFD context diagram for online food ordering system level 0 dfd for food ordering system er diagram for online food ordering system data flow diagram example for online shopping data flow diagram level 0 1 2 examples data flow diagram symbols level 2 dfd for online food ordering system data flow diagram for pizza ordering system
Read more

What is DFD ? or What is Data Flow Diagram?

A data-flow diagram ( DFD ) is a graphical representation of the "flow" of data through an information system. DFDs can also be used for the visualization of data processing ( structured design ). On a DFD , data items flow from an external data source or an internal data store to an internal data store or an external data sink, via an internal process . A DFD provides no information about the timing or ordering of processes, or about whether processes will operate in sequence or in parallel. It is therefore quite different from a flowchart, which shows the flow of control through an algorithm, allowing a reader to determine what operations will be performed, in what order, and under what circumstances, but not what kinds of data will be input to and output from the system, nor where the data will come from and go to, nor where the data will be stored (all of which are shown on a DFD ). ...
Read more

Rules for Stopping the Decomposition Process in DFD

Rules for Stopping the Decomposition Process in DFD (1) when you have reduced each process to a single decision or calculation or to a single database operation;  (2) when each data store represents data about a single entity;  (3) when the system user does not care to see any more detail or when you and other analysts have documented sufficient detail to do subsequent systems development tasks;  (4) when every data flow does not need to be split further to show that different data are handled in different ways;  (5) when you believe that you have shown each business form or transaction, computer on-line display, and report as a single data flow;  (6) when you believe there is a separate process for each choice on all lowest-level menu options for the system.
Read more