17. Data Flow Diagrams (cont)

Practice makes perfect

It takes a bit of organisation and practice to learn how to break down a system into well-separated processes and data flows.

For example, a company hires a management consultant to improve the efficiency of a department. She may use a Data Flow Diagram to show how the department works at the moment. The DFD can be used as a tool for a discussion with the team to show where duplication of effort is happening or redundant, dead-end processes are taking place because 'We have always done it that way'.

The consultant may then show a new DFD to show the improved processes and data flows.

There are no hard-and-fast way of analysing a system, but an approach is sketched out below.

1. If possible, interview everyone within the system to find out what data they use, what do they do with that data, what data stores do they use and which external systems / departments / people do they need to liaise with.

2. Draw an outline DFD for each person / team. Check back with them to ensure that all the relevant data flows are in place along with the correct process handling.

3. Take two of the DFDs and note common processes / data flows / stores / external entities and combine them.

4. Take the next DFD and combine that one as well.
Gradually an overall picture of the system emerges.

If it is complicated, then some processes may include sub-processes as Level 1 and Level 2 DFDs.

If the exercise is to spot inefficiencies, then does the DFD show redundant work being carried out, is there duplication of effort going on, are there bottlenecks happening? Can they be avoided or removed? And so on.

Summary

The Data Flow Diagram is an excellent analysis tool for understanding how a system or organisation works.