30079_26a.pdf

PART 2

SYSTEMS AND CONTROLS

CHAPTER 26

SYSTEMS ENGINEERING:

ANALYSIS, DESIGN, AND

INFORMATION PROCESSING

FOR ANALYSIS AND DESIGN

Andrew P. Sage

School of Information Technology and Engineering

George Mason University

Fairfax, Virginia

26.1 INTRODUCTION

763

26.5 SYSTEMDESIGN

784

26.5.1 The Purposes of Systems

Design

26.2 THESYSTEMLIFECYCLE

AND FUNCTIONAL

ELEMENTS OF SYSTEMS

ENGINEERING

784

26.5.2 Operational Environments

and Decision Situation

Models

765

785

26.5.3 The Development of Aids

for the Systems Design

Process

26.3 SYSTEMS ENGINEERING

OBJECTIVES

786

770

26.5.4 Leadership Requirements

for Design 789

26.5.5 System Evaluation 790

26.5.6 Evaluation Test Instruments 791

26.4 SYSTEMSENGINEERING

METHODOLOGY AND

METHODS

771

26.4.1 Issue Formulation

771

26.4.2 Issue Analysis

775

26.6 CONCLUSIONS

792

26.4.3 Information Processing by

Humans and Organizations 779

26.4.4 Interpretation

782

26.4.5 The Central Role of

Information in Systems

Engineering

783

26.1 INTRODUCTION

Systems engineering is a management technology. Technology involves the organization and delivery

of science for the (presumed) betterment of humankind. Management involves the interaction of the

organization, and the humans in the organization, with the environment. Here, we interpret environ-

ment in a very general sense to include the complete external milieu surrounding individuals and

organizations. Hence, systems engineering as a management technology involves three ingredients:

science, organizations, and their environments. Information, and knowledge, is ubiquitous throughout

systems engineering and management efforts and is, in reality, a fourth ingredient. Systems engi-

neering is thus seen to involve science, organizations and humans, environments, technologies, and

information and knowledge.

The process of systems engineering involves working with clients in order to assist them in the

organization of information and knowledge to aid in judgment and choice of activities. These activities

result in the making of decisions and associated resource allocations through enhanced efficiency,

effectiveness, equity, and explicability as a result of systems engineering efforts.

Mechanical Engineers' Handbook, 2nd ed., Edited by Myer Kutz.

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 implementation.

In this chapter, we are concerned with the engineering of large-scale systems, or systems engi-

neering. l We are especially concerned with strategic level systems engineering, or systems manage-

ment. 2 We begin by first discussing the need for systems engineering and then 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 engineering processes. This is used to

motivate discussion of the functional levels, or considerations, involved in systems engineering efforts:

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 management, behavioral, and math-

ematical constructs to identify, structure, analyze, evaluate, and interpret generally incomplete, un-

certain, imprecise, and otherwise imperfect information. 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 appropriate 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 tech-

nology 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.

• Institutional and organizational considerations play an important role.

• There is a need for explicit and explicable consideration of the efficiency, effectiveness, and

equity of alternative courses of action.

There are a number of results potentially attainable from use of systems engineering approaches.

These include:

• Identification of perceived needs in terms of identified objectives and values of a client group

• Identification or definition of a set of user or client requirements for the product system or

service system that will ultimately be fielded

• Enhanced identification of a wide range of proposed alternatives or policies that might satisfy

these needs, achieve the objectives of the clients in a high-quality and trustworthy fashion,

and fulfill the requirements definition

• Increased understanding of issues that led to the effort, and the impacts of alternative actions

upon these issues

• Ranking of these identified alternative courses of action in terms of the utility (benefits and

costs) in achieving objectives, satisfying needs, and fulfilling requirements

• A set of alternatives that is selected for implementation, generally by a group of content

specialists responsible for detailed design and implementation, and an appropriate plan for

action to achieve this implementation

Ultimately the action plans result in a working product or service and are maintained over time in

subsequent phases of the post-deployment efforts that also involve systems engineering.

To develop professionals capable of coping satisfactorily with diverse factors involved in wide-

scope problem-solving is a primary goal of systems engineering and systems engineering education.

This does not imply that a single individual or even a small group can, despite its strong motivation,

solve all of the problems involved in a systems study. Such a requirement would demand total and

absolute intellectual maturity on the part of the systems engineer and such is surely not realistic. It

is also unrealistic to believe that issues can be resolved without very close association with a number

of people who have stakes, and who thereby become stakeholders, in problem-solution efforts. Con-

sequently, systems engineers must be capable of facilitation and communication of knowledge be-

tween the diverse group of professionals, and their publics, that are involved in wide-scope

problem-solving. This requires that systems engineers be knowledgeable and able to use not only the

technical methods-based tools that are needed for issue and problem resolution, but the behavioral

constructs and management abilities that are also needed for resolution of complex, large-scale prob-

lems. Intelligence, imagination, and creativity are necessary but not sufficient for proper use of the

procedures of systems engineering. Facility in human relations and effectiveness as a broker of

information among parties at interest in a systems engineering program are very much needed as

well.

It is this blending of the technical, managerial, and behavioral that is a normative goal of success

for systems engineering education and for systems engineering professional practice. Thus, systems

engineering involves

• The sciences and the various methods, analysis, and measurement perspectives associated with

the sciences

• Life-cycle process models for definition, development, and deployment of systems

• The systems management issues associated with choice of an appropriate process

• Organizations and humans, and the understanding of organizational and human behavior

• Environments and understanding of the diverse interactions of organizations of people, tech-

nologies, and institutions with their environments

• Information, and the way in which it can and should be processed to facilitate all aspects of

systems engineering efforts

Successful systems engineering must be practiced at three levels: systems methods and measure-

ments, systems processes and methodology, and systems management. Systems engineers must be

aware of a wide variety of methods that assist in the formulation, analysis, and interpretation of

contemporary issues. They must be familiar with systems engineering process life cycles (or meth-

odology, as an open set of problem-solving procedures) in order to be able to select eclectic ap-

proaches that are best suited to the task at hand. Finally, a knowledge of systems management is

necessary in order to be able to select life-cycle processes that are best matched to behavioral and

organizational concerns and realities.

All three of these levels, suggested in Fig. 26.1, are important. To neglect any of them in the

practice of systems engineering is to invite failure. It is generally not fully meaningful to talk only

of a method or algorithm as a useful system-fielding or life-cycle process. It is ultimately meaningful

to talk of a particular process as being useful. A process or product line that is truly useful for the

fielding of a system will depend on the methods that are available, the operational environment, and

leadership facets associated with use of the system and the system fielding process. Thus systems

management, systems engineering processes, and systems engineering methods and measurements

do, separately and collectively, play a fundamental role in systems engineering.

26.2 THE SYSTEM LIFE CYCLE AND FUNCTIONAL ELEMENTS OF SYSTEMS

ENGINEERING

We have provided one definition of systems engineering thus far. It is primarily a structural and

process-oriented definition. A related definition, in terms of purpose, is that "systems engineering is

management technology to assist and support policy-making, planning, decision-making, and asso-

ciated resource allocation or action deployment for the purpose of acquiring a product desired by

customers or clients. Systems engineers accomplish this by quantitative and qualitative formulation,

analysis, and interpretation of the impacts of action alternatives upon the needs perspectives, the

institutional perspectives, and the value perspectives of their clients or customers." Each of these

three steps is generally needed in solving systems engineering problems. Issue formulation is an

effort to identify the needs to be fulfilled and the requirements associated with these in terms of

objectives to be satisfied, constraints and alterables that affect issue resolution, and generation of

potential alternative courses of action. Issue analysis enables us to determine the impacts of the

identified alternative courses of action, including possible refinement of these alternatives. Issue

Fig. 26.1 Conceptual illustration of the three levels for systems engineering.

interpretation enables us to rank in order the alternatives in terms of need satisfaction and to select

one for implementation or additional study. This particular listing of three systems engineering steps

and their descriptions is rather formal. Often, issues are resolved this way. The steps of formulation,

analysis, and interpretation may also be accomplished on as "as-if" basis by application of a variety

of often useful heuristic approaches. These may well be quite appropriate in situations where the

problem-solver is experientially familiar with the task at hand and the environment into which the

task is imbedded. 1

The key words in this definition are "formulation," "analysis," and "interpretation." In fact, all

of systems engineering can be thought of as consisting of formulation, analysis, and interpretation

efforts, together with the systems management and technical direction efforts necessary to bring this

about. We may exercise these in a formal sense throughout each of the several phases of a systems

engineering life cycle, or in an "as-if" or experientially based intuitive sense. These formulation,

analysis, and interpretation efforts are the step-wise or microlevel components that comprise a part

of the structural framework for systems methodology. They are needed for each phase in a systems

engineering effort, although the specific formulation methods, analysis methods, and interpretation

methods may differ considerably across the phases.

We can also think of a functional definition of systems engineering: "Systems engineering is the

art and science of producing a product, based on phased efforts, that satisfies user needs. The system

is functional, reliable, of high quality, and trustworthy, and has been developed within cost and time

constraints through use of an appropriate set of methods and tools."

Systems engineers are very concerned with the appropriate definition, development, and deploy-

ment of product systems and service systems. These comprise a set of phases for a systems engi-

neering life cycle. There are many ways to describe the life-cycle phases of the systems engineering

process, and we have described a number of them in Refs. 1 and 2. Each of these basic life-cycle

models, and those that are outgrowths of them, is comprised of these three phases of definition,

development, and deployment. For pragmatic reasons, a typical life cycle will almost always contain

more than three phases. Often, it takes on the "waterfall" pattern illustrated in Fig. 26.2, although

there are a number of modifications of the basic waterfall, or "grand-design," life cycles that allow

for incremental and evolutionary development of systems life-cycle processes. 2

A successful approach to systems engineering as an intellectual and action-based approach for

increased innovation and productivity and other contemporary challenges must be capable of issue

formulation, analysis, and interpretation at the level of institutions and values as well as at the level

of symptoms. Systems engineering approaches must allow for the incorporation of need and value

perspectives as well as technology perspectives into models and postulates used to evolve and evaluate

policies or activities that may result in technological and other innovations.

In actual practice, the steps of the systems process (formulation, analysis, and interpretation) are

applied iteratively, across each of the phases of a systems engineering effort, and there is much

feedback from one step to the other. This occurs because of the learning that is accomplished in the

process of problem-solution. Underlying all of this is the need for a general understanding of the

diversity of the many systems engineering methods and algorithms that are available and their role

in a systems engineering process. The knowledge taxonomy for systems engineering, which consists

Plik z chomika:

Inne pliki z tego folderu:

Inne foldery tego chomika: