Page 277 - Mechanical Engineers' Handbook (Volume 2)

268 Analysis, Design, and Information Processing

issue formulation effort is concerned primarily with identification and description of the
elements of the issue under consideration, with, perhaps, some initial effort at structuring
these in order to enhance understanding of the relations among these elements. Structural
concerns are also of importance in the analysis effort. The systems process is iterative and
interactive, and the results of preliminary analysis are used to refine the issue formulation
effort. Thus, the primary intent of issue formulation is to identify relevant elements that
represent and are associated with issue definition, the objectives that should be achieved in
order to satisfy needs, and potential action alternatives.
There are at least four ways to accomplish issue formulation, or to identify requirements
for a system, or to accomplish the initial part of the definition phase of systems engineering:

1. Asking stakeholders in the issue under consideration for the requirements
2. Descriptive identification of the requirements from a study of presently existing sys-
tems
3. Normative synthesis of the requirements from a study of documents describing what
‘‘should be,’’ such as planning documents
4. Experimental discovery of requirements, based on experimentation with an evolving
system
These approaches are neither mutually exclusive nor exhaustive. Generally, the most appro-
priate efforts will use a combination of these approaches.
There are conflicting concerns with respect to which blend of these requirement iden-
tification approaches is most appropriate for a specific task. The asking approach seems very
appropriate when there is little uncertainty and imprecision associated with the issue under
consideration, so that the issue is relatively well understood and may be easily structured,
and where members of the client group possess much relevant expertise concerning the issue
and the environment in which the issue is embedded. When these characteristics of the
issue—lack of imprecision and presence of expert experiential knowledge—are present, then
a direct declarative approach based on direct ‘‘asking’’ of ‘‘experts’’ is a simple and efficient
approach. When there is considerable imprecision or a lack of experiential familiarity with
the issue under concern, the other approaches take on greater significance. The asking ap-
proach is also prone to a number of human information-processing biases, as will be dis-
cussed in Section 4.5. This is not as much of a problem in the other approaches.
Unfortunately, however, there are other difficulties with each of the other three ap-
proaches. Descriptive identification, from a study of existing systems of issue formulation
elements, will very likely result in a new system that is based or anchored on an existing
system and tuned, adjusted, or perturbed from this existing system to yield incremental
improvements. Thus, it is likely to result in incremental improvements to existing systems
but not to result in major innovations or totally new systems and concepts.
Normative synthesis from a study of planning documents will result in an issue for-
mulation or requirement identification effort that is based on what have been identified as
desirable objectives and needs of a client group. A plan at any given phase may well not
exist or it may be flawed in any of several ways. Thus, the information base may well not
be present or may be flawed. When these circumstances exist, it will not be a simple task
to accomplish effective normative synthesis of issue formulation elements for the next phase
of activity from a study of planning documents relative to the previous phase.
Often it is not easily possible to determine an appropriate set of issue formulation
elements or requirements. Often it will not be possible to define an appropriate set of issue
formulation efforts prior to actual implementation of a preliminary system design. There are
many important issues where there is an insufficient experiential basis to judge the effect-