Introduction to Systems Engineering Fundamentals

Scope of System Thinking

The world we live in has numerous kinds of systems that influence our daily life. Some examples of the use of the word system in everyday usage are education system, transport system, solar system, telephone system, Dewey decimal system, weapons system, ecological system, space system, and so on; there is almost no end to the uses of the word “system” that come to mind

The word “system” is used in all areas of human activity and at all levels but what do people mean when they use the word “system” and is there some part of the meaning that is common to all applications? These and similar questions, all relating to the use of the word “system” in everyday language, need to be given careful consideration if we are to achieve a clear understanding of the underlying concepts of Systems Thinking (Glossary) before specializing to the engineering context.

If we define the general idea of System (Glossary) as a set of system elements with defined relationships within a system boundary, and observable collective identify or behavior outside the boundary; then we can related this simple concept to the real world through three related system domains, as follows.

insert diagram here

Natural Systems are real world phenomena to which we apply system thinking to help us better understand what they do and how they do it. A truly natural system would be a system can observe and reason about, but over which we cannot exercise control, such as the solar system. As shown above, there are some managed natural systems which fall under the scope of one or both of the other domains. For Engineered Systems (ES) and Social Systems (SS), the best way to define the domain scope is to identify the types of systems for which we have authority to commit and manage resources for system creation and sustainment, and responsibility for the results. Purely technical systems such as bridges, electric autos, and power generation and distribution systems are exclusively in the ES domain, while purely human systems such as legislatures, conservation foundations, and the United Nations (UN) Security Council are exclusively in the SS domain. These systems are purely human artifacts, created to help us gain some kind of control over or protection from the real world.

Systems common to both the SS and ES domains such as water and power management and safety governance systems, and water and power safety assurance systems, are often called socio-technical systems. The systems common to the ES and NS domains such as dams and flood control systems might equally be termed as environ-technical systems, although the term socio-technical is often extended to cover both. The behavior of such systems is determined both by the nature of the engineered elements and by their ability to integrate with or deal with the variability of the natural the social systems in which they sit. The ultimate success of any engineered system is thus measured in its ability to contribute to the success of relevant socio (or enviro) technical systems.

System Definitions – a discussion

How is “System” defined in the Systems Engineering literature? Systems Engineers generally refer to their system-of-interest as “the system,” and their definitions of “system” tend to characterize Engineered Systems. Two examples are:

• “A system is an array of components designed to accomplish a particular objective according to plan.” (Johnson, Kast, and Rosenzweig, 1963).
• “A system is defined as a set of concepts and/or elements used to satisfy a need or requirement.” (Miles, 1973).

The INCOSE Handbook generalizes this idea of an engineered system as: “An interacting combination of elements to accomplish a defined objective. These include hardware, software, firmware, people, information, techniques, facilities, services, and other support elements.” (INCOSE 2008).

However, engineered systems often find that their environment includes Natural Systems that don’t follow the definitions of “system” above, in that they have not been defined to satisfy a requirement or come into being to satisfy a defined objective. These include such systems as the solar system, if one’s engineered system is an interplanetary spacecraft. This has led to more general definitions of “system such as the following (Aslaksen 2004):

A system consists of three related sets:

• a set of elements;
• a set of internal interactions between the elements; and
• a set of external interactions between one or more elements and the external world; i.e. interactions that can be observed from outside the system.

This definition of “system” enables people to reason about numerous classes of dynamical systems that involve both Engineered Systems and Natural Systems. But again, there are many systems in which the elements do not interact. They just are, such as the real number system used in engineering calculations; or they evolve to include new elements such as the rare earths and transuranium elements in the periodic system of chemical elements, or the classes of book topics in the Dewey decimal system. Also relationships between elements may not be physical, such as the relationships between the efficiency of operations, degree of interpersonal trust, and degree of honoring commitments in Social Systems operating with interpersonal tacit knowledge vs. explicit documented knowledge (Nonaka-Takeuchi 1995) that are the basis for agile methods.

Natural Systems and Social Systems often form part of the environment in which Engineered Systems need to function. Often also, the characteristics of Engineered Systems, Natural Systems and Social Systems need to be integrated to achieve the objective of “enabling the realization of successful systems” in the definition of systems engineering.

Thus, when we consider systems in a scientific or engineering way we are always interested the ways in which changes to engineered or social systems affect the ability of a socio-technical system to exist within its natural and social environments and to satisfy some interest of the observer or inquirer.

System Context

As can be seen from the discussion above, most attempts to define the term system either include in them assumptions about the system domain being considered, or are so abstract and general as to be of little practical use.

The reason we use the concept of a system is to help make sense of the complexity (Glossary) of the real world. This is done either by creating an abstract system to help explain complex situations, such as the real number system; by creating a standardized approach to common problems, such as the Dewey system; or by agreeing on a model of a new situation to allow it to be further explored, such as a scientific theory or conceptual system design. People use systems to make sense of complexity in an individual way, and when they work together to solve problems.

In the Systems Approach (Glossary) we use several system viewpoints, and a given element may be included in several system views. Thus, it is less important that we can define “the system” than it is that we can use combinations of systems to help achieve a purpose.

We use the idea of a System Context (Glossary) to define an Engineered System of Interest, and to capture and agree the important relationships between it the systems it works directly with and the systems which influence it in some way. All application of a Systems Approach (and hence of SE) are applied to a System Context, and not to an individual system.

References

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Citations

INCOSE 2008, INCOSE Handbook Issoue 3.2

Johnson, R.A. 1963. F.W. Kast, and J.E. Rosenzweig, The Theory and Management of Systems, McGraw-Hil.

Miles, R.F. (ed.)1973. System Concepts, Wiley.

Aslaksen, E.W. 2004, ???.

Nonaka, Ikujiro; Takeuchi, Hirotaka (1995), The knowledge creating company: how Japanese companies create the dynamics of innovation, New York: Oxford University Press, pp. 284, ISBN 9780195092691

Primary References

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Additional References

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