Data Flow Diagram - Validating DFD


Validating the DFD

Before moving on from this initial high-level DFD, we must ensure it is consistent. Below is a checklist of points to watch out for before moving on to a detailed investigation which will take us to lower levels.

1.   Has each process a strong imperative verb and object?
2.   Are data flows in related to data flows out? Data should not be swallowed up by a process, only transformed in some way. A data store is the only place data is allowed to rest. Similarly, data cannot be generated by a process. A document may be, but the data on the document comes from a data flow into that process.
3.   Can the flows be reduced? If a process is too busy, it can perhaps be broken down into two or more processes: six data flows in or out of a process should be enough.
4.   Do all data stores have flows both in and out? A one-way data store is of little use, unless it is a reference file. If the Current Physical DFD should identify such a data store, confirm with the User that you have correctly understood the procedures.
5.   Are symbols correctly labelled and uniquely referenced?
6.   Do all external entities communicate with a process? No entity should be allowed direct access to data, either to read or to update it.

Comments

Popular posts from this blog

Food Ordering System

Rules for Stopping the Decomposition Process in DFD