BIS - IDEF0

IDEF0 is a static modelling paradigm that represents a system as a network of inter-connected activities. It uses a mix of graphics and natural language to capture and communicate process details. By adding explanations in a glossary it is possible to capture a very rich set of process knowledge.

It suits business, data processing and manufacturing systems because these systems generally consist of a network of inter-connected activities. The models are hierarchical. They start with a single activity at the highest level. This activity is then decomposed into three to six activities on the next page. If it is helpful for the purpose of the model, those activities in turn are decomposed. IDEF0 is a public domain modelling system and in fact it is an American standard (FIPS 183). IDEF0 can be used to produce structured documentation suitable for ISO 9000.

The hierarchical structure means that each page of the model contains a relatively small amount of information. This is a contrast to flow charts that can have many different activities on the one page - IDEF0 models do not lend themselves to papering walls! Another feature that makes IDEF0 models easy to understand is that the methodology only contains two elements - boxes and arrows. The boxes represent the activities.

The arrows represent the inputs, outputs, controls and mechanisms of those activities. The inputs are transformed in the activity using, but not consuming, mechanisms or resources such as staff and machines to produce outputs. Typically the operation of the activity will be moderated by controls such as policies and procedures. An example of the top level of an IDEF0 model is shown right.

Although the actual decomposition page is not shown in this way the following diagram illustrates how activities are decomposed.

As well as providing an excellent communication medium so that changes are understood widely in an organisation the rigour of the methodology has major benefits. The question, 'if these inputs undergo this activity are they transformed into these outputs by these mechanisms?' is a simple but powerful check of reality. Answering this question satisfactorily for each activity leads to an overall model that is correct.