The Psychology of Quality and More

IDEF0 - Part 2 (doing it)

Quality Tools > Tools of the Trade > 20: IDEF0 - Part 2 (doing it)

Last time, we discussed the approach and structure of IDEF0 as a method for process documentation. This month we are taking the logical next step of getting into the practicalities of actually doing it.

How to do it

1. Identify the system to be documented and how the diagrams will be used in the future. Also decide from whose viewpoint the diagrams will be drawn. Each of these points is likely to affect later decisions about what to include and emphasise in the diagrams.

2. Gather information about the system, both reading available documentation and by interviewing people who work in and with the process. Use a series of interviews, developing the process from the top down.

Identify first the ICOM items around the process (Inputs, Controls, Outputs and Mechanisms) in a Data List, then identify the activities that produce and use them. Start to build the diagram through a structured note-taking method as below.

3. Start drawing the process from the top, A-0 diagram, as below, indicating purpose and main viewpoint on the diagram to help set the overall context. As this simple diagram defines the boundaries of the process, it can take a long time to complete.

4. Break down each activity box into lower-level activity diagrams, preserving the ICOM arrows in the lower-level diagrams (show any change from this with tunnelling, as described last time). At any level, it may be decided not to break any box down further.

Draw inputs and outputs first, then add controls and mechanisms. Combine and split arrows to help simplify the diagram and ease understanding for the reader.

Place boxes in diagrams in order of dominance, with higher-dominance diagrams top left and other boxes cascading diagonally down to the bottom right. This will help arrows to flow tidily.

Name and number the finished diagram.

5. Include text pages within the system to describe aspects of the diagram in more detail. Each ICOM item may have a few lines of text to describe it. Such pages are usually numbered with a G number (for 'Glossary'). Glossary pages for activities have a 'T' number.

6. Verify diagrams after each layer with the people involved in the process. This is typically done with the reviewer writing on the diagram in red ink. Write your own counter-comments in blue ink (indicating either agreement or reasons for disagreement.

Next time: Voting variants

This article first appeared in Quality World, the journal of the Institute for Quality Assurance