Page 267 - Mechanical Engineers' Handbook (Volume 2)

258 Analysis, Design, and Information Processing

that lead to the engineering of trustworthy systems. These activities result in the making of
decisions and associated resource allocations through enhanced efficiency, effectiveness, eq-
uity, and explicability as a result of systems engineering efforts.
This set of action alternatives is selected from a larger set, in accordance with a value
system, in order to influence future conditions. Development of a set of rational policy or
action alternatives must be based on formation and identification of candidate alternative
policies and objectives against which to evaluate the impacts of these proposed activities,
such as to enable selection of efficient, effective, and equitable alternatives for implemen-
tation.
In this chapter, we are concerned with the engineering of large-scale systems, or systems
1
engineering. We are especially concerned with strategic-level systems engineering, or sys-
tems management. We begin by first discussing the need for systems engineering and then
2
providing some definitions of systems engineering. We next present a structure describing
the systems engineering process. The result of this is a life-cycle model for systems engi-
neering processes. This is used to motivate discussion of the functional levels, or consider-
ations, involved in systems engineering efforts: measurements, systems engineering methods
and tools, systems methodology or processes, and systems management. Considerably more
details are presented in Refs. 1 and 2, which are the sources from which most of this chapter
is derived.
Systems engineering is an appropriate combination of mathematical, behavioral, and
management theories in a useful setting appropriate for the resolution of complex real-world
issues of large scale and scope. As such, systems engineering consists of the use of man-
agement, behavioral, and mathematical constructs to identify, structure, analyze, evaluate,
and interpret generally incomplete, uncertain, imprecise, and otherwise imperfect informa-
tion. When associated with a value system, this information leads to knowledge to permit
decisions that have been evolved with maximum possible understanding of their impacts. A
central need, but by no means the only need, in systems engineering is to select an appro-
priate life cycle, or process, that is explicit, rational, and compatible with the implementation
framework extant and the perspectives and knowledge bases of those responsible for decision
activities. When this is accomplished, an appropriate choice of systems engineering methods
and tools may be made to enable full implementation of the life-cycle process.
Information is a very important quantity that is assumed to be present in the management
technology that is systems engineering. This strongly couples notions of systems engineering
with those of technical direction or systems management of technological development,
rather than exclusively with one or more of the methods of systems engineering, important
as they may be for the ultimate success of a systems engineering effort. It suggests that
systems engineering is the management technology that controls a total system life-cycle
process, which involves and which results in the definition, development, and deployment of
a system that is of high quality, trustworthy, and cost-effective in meeting user needs. This
process-oriented notion of systems engineering and systems management will be emphasized
here.
Among the appropriate conditions for use of systems engineering are the following:
• There are many considerations and interrelations.
• There are far-reaching and controversial value judgments.
• There are multidisciplinary and interdisciplinary considerations.
• The available information is uncertain, imprecise, incomplete, or otherwise flawed.
• Future events are uncertain and difficult to predict.