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Levels of Abstraction in IDEF0 Models

As stated, the breakdown approach used in IDEF0 modeling decomposes selected activities into finer and finer levels of detail. The resultant model set includes sufficient detail to plan and control the implementation of changes to the enterprise.

An IDEF0 model may also contain multiple levels of abstraction. To understand what is meant by “level of abstraction,” let’s consider a typical enterprise. Each level of management has its natural level of abstraction. Top management must think in broad terms, taking into account many viewpoints as well as abstractions of the details of what is going on in the enterprise. An upper-level manager cannot possibly understand every detail of all of the activities in the entire enterprise, but he must abstract business processes and characteristics that are important at his level of abstraction. He must consider such things as overall profit, hiring policies, or the quality of the enterprise’s product line, rather than the specific factors that go into these high-level abstractions.

Conversely, a manager at a lower level needs fine-level detail about a specific topic from a single viewpoint, and he may get uneasy thinking in general terms. His level of abstraction is concerned with such things as the cost of raw materials, the capabilities of specific staff members, or the quality of the service for which he is responsible.

The model’s level of abstraction is independent of its level of detail. That is, after selecting a level of abstraction to model, the author may decompose the activities to whatever level of detail he requires to satisfy the purpose of the model. However, if the purpose of the model requires information at a different level of abstraction, no amount of further detailing at the present level of abstraction will provide the needed information. Modeling at all required levels of abstraction must be completed to satisfy the enterprise analysis requirements.

The IDEF0 concept of a mechanism is different from the concept of level of abstraction. In IDEF0, a mechanism represents who performs the activity and what tools (software packages and equipment) are required to perform the activity. In other words, the mechanism identifies the resources needed to perform the function. A mechanism is therefore at a lower level of abstraction than the activity box it implements.

The fact that the mechanism depicts a lower level of abstraction does not mean that it cannot be modeled in IDEF0. It just means that the mechanism is shown as an arrow entering the bottom of the box, and that a separate model must be examined to understand how the mechanism works (see Figure 3-9).

Figure 3-9

Figure 3-9: Mechanism at a Lower Level of Abstraction.

The IDEF0 diagram in Figure 3-9 shows Activity A23 (Edit Document) using the word processor support mechanism. The IDEF0 model for the word processor is shown at the lower-right corner of Figure 3-9. What this tells us is that any word processor mechanism may be modeled and plugged into the diagram to show the precise activity performed when editing a document with any variety of word processors. This shows how the editing is done using the mechanism, and therefore indicates that there is a drop in level of mechanization from what is done to the document by the EDIT activity.

To accomplish the reengineering of an enterprise, an analyst may need to show multiple levels of abstraction and several levels of mechanism, as well as how those are integrated to perform the processes of the enterprise. Showing all this provides a clear, accurate big picture of the overall operation of the enterprise.

In addition to an IDEF0 process-oriented analysis, various additional analysis methods may be applied, using the IDEF0 model as a baseline. For example, the analyst may need to know where costs and labor are being expended, in order to estimate the return on investment of potential changes or to understand the impact of introducing new technology. Various analyses, such as activity-based costing (ABC) and work flow simulation, are typically applied using the IDEF0 model as a baseline.

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