Data Flow Diagram - How to Evaluate DFD for Correctness

Evaluating Data Flow Diagrams for Correctness

It is essential to evaluate all DFDs carefully to determine if they are correct. Errors, omissions and inconsistencies can occur for several reasons, including mistakes in drawing the diagrams. But the presence of what appears to be an error may in fact point out a deficiency in the system or a situation in which users are not aware of how certain processes operate.

These questions are useful in evaluating data flow diagrams:

·   Are there any unnamed components in the data flow diagram (data flows, processes, stores, inputs or outputs)?

           

·   Are there any data stores that are input but never referenced?

           

·   Are there any processes that do not receive input?

           

·   Are there any processes that do not produce output?

           

·   Are there any processes that serve multiple purposes? If so, simplify by exploding them into multiple processes that can be better studied).

           

·   Are there data stores that are never referenced?

           

·   Is the inflow of data adequate to perform the process?

           

·   Is there excessive storage of data in a data store (more than the necessary details)?

           

·   Is the inflow of data into a process too much for the output that is produced?

           

·   Are aliases introduced in the system description?

           

·   Is each process independent of other processes and dependent only on the data it receives as input?