Page 279 - Mechanical Engineers' Handbook (Volume 2)

270 Analysis, Design, and Information Processing

structure knowledge elements such that they are capable of being better understood and
communicated.
We now discuss several formal methods appropriate for ‘‘asking’’ as a method of issue
formulation. Most of these, and other, approaches are described in Refs. 1, 3, and 4. Then
we shall very briefly contrast and compare some of these approaches. The methods associated
with the other three generic approaches to issue formulation also involve approaches to
analysis that will be discussed in the next section.
Several of the formal methods that are particularly helpful in the identification, through
asking, of issue formulation elements are based on principles of collective inquiry, in which
interested and motivated people are brought together to stimulate each other’s creativity in
generating issue formulation elements. We may distinguish two groups of collective-inquiry
methods:
1. Brainwriting, Brainstorming, Synectics, Nominal Group Technique, and Charette.
These approaches typically require a few hours of time, a group of knowledgeable
people gathered in one place, and a group leader or facilitator. Brainwriting is typi-
cally better than brainstorming in reducing the influence of dominant individuals.
Both methods can be very productive: 50–150 ideas or elements might be generated
in less than an hour. Synectics, based on problem analogies, might be appropriate if
there is a need for truly unconventional, innovative ideas. Considerable experience
with the method is a requirement, however, particularly for the group leader. The
nominal group technique is based on a sequence of idea generation, discussion, and
prioritization. It can be very useful when an initial screening of a large number of
ideas or elements is needed. Charette offers a conference or workshop-type format
for generation and discussion of ideas and/or elements.
2. Questionnaires, Surveys, and Delphi. These three methods of collective-inquiry mod-
eling do not require the group of participants to gather at one place and time, but
they typically take more time to achieve results than the first group of methods. In
questionnaires and surveys, a usually large number of participants are asked, on an
individual basis, for ideas or opinions, which are then processed to achieve an overall
result. There is no interaction among participants. Delphi usually provides for written
interaction among participants in several rounds. Results of previous rounds are fed
back to participants, who are asked to comment, revise their views as desired, and
so on. A Delphi exercise can be very instructive but usually takes several weeks or
months to complete.

Use of most structuring methods, in addition to leading to greater clarity of the problem
formulation elements, will also typically lead to identification of new elements and revision
of element definitions. As we have indicated, most structuring methods contain an analytical
component; they may, therefore, be more properly labeled analysis methods. The following
element-structuring aids are among the many modeling aids available:
• Interaction matrices may be used to identify clusters of closely related elements in a
large set, in which case we have a self-interaction matrix, or to structure and identify
the couplings between elements of different sets, such as objectives and alternatives.
In this case, we produce cross-interaction matrices, such as shown in Fig. 5. Interaction
matrices are useful for initial, comprehensive exploration of sets of elements. Learning
about problem interrelationships during the process of constructing an interaction ma-
trix is a major result of use of these matrices.
• Trees are graphical aids particularly useful in portraying hierarchical or branching-
type structures. They are excellent for communication, illustration, and clarification.
Trees may be useful in all steps and phases of a systems effort. Figure 6 presents an