SEBoK Introduction

Systems engineering (SE) is essential to the success of many human endeavors. Today, SE is increasingly recognized worldwide for its importance in the development, deployment, operation, and evolution of systems with a wide variety of scale, complexity, and purpose.

The purpose of the SEBoK is to provide a consensus-based, evolvable baseline of SE knowledge that strengthens mutual understanding among SE practitioners and the people in other disciplines with whom they interact. Shortfalls in such mutual understanding are a major source of system failures, which have increasingly severe impacts as systems become more globally interactive and critical to people’s health, security, and quality of life.

A good first step towards understanding is to define key terms. Four terms will suffice for this Introduction: system, engineered system, systems engineering, and systems engineer.

Here are baseline definitions of what these terms mean for the purposes of the SEBoK:

• A system is “a set of elements and a set of inter-relationships between the elements such that they form a bounded whole relative to the elements around them” (Bertalanffy 1968) and which exists in an environment which contains related systems and conditions. While there are many definitions of the word “system,” the SEBoK authors believe that this definition encompasses most of those which are relevant to systems engineering.

• An engineered system is an open system of technical or sociotechnical elements that exhibits emergent properties not exhibited by its individual elements. It is created by and for people; has a purpose, with multiple views; satisfies key stakeholders’ value propositions; has a life cycle and evolution dynamics; has a boundary and an external environment; and is part of a system-of-interest hierarchy.

• Systems engineering is “an interdisciplinary approach and means to enable the realization of successful systems” (INCOSE 2011). It focuses on holistically and concurrently understanding stakeholder needs; exploring opportunities; documenting requirements; and synthesizing, verifying, validating, and evolving solutions while considering the complete problem, from system concept exploration through system disposal.

• A systems engineer is “a person who practices systems engineering” as defined above, and whose systems engineering capabilities and experience include sustained practice, specialization, leadership or authority over systems engineering activities. Systems engineering activities may be conducted by any competent person regardless of job title or professional affiliation.

To download a PDF of Part 1, please click here.

Part 1 Articles

Articles in Part 1 include:

• Scope and Context of the SEBoK
• Structure of the SEBoK
• Economic Value of Systems Engineering
• Systems Engineering: Historic and Future Challenges
• Systems Engineering and Other Disciplines
• SEBoK Users and Uses
• SEBoK Evolution
• Acknowledgements

Purpose of the SEBoK

The purpose of the SEBoK is to provide a consensus-based, evolvable baseline of SE knowledge that strengthens mutual understanding among SE practitioners and the people in other disciplines with whom they interact. Shortfalls in such mutual understanding are a major source of system failures. Ongoing studies of system cost and schedule failures (Gruhl-Stutzke 2005; Johnson 2006) and safety failures (Leveson 2012) have shown that the failures have mostly come not from their domain disciplines, but from lack of adequate SE.

To provide a foundation for the desired mutual understanding, the SEBoK describes the boundaries, terminology, content, and structure of systems engineering (SE). In so doing, the SEBoK systematically and consistently supports six broad purposes, described in Table 1.

Table 1. SEBoK Purposes (Table Developed for BKCASE)

	Purpose	Description
1	Inform Practice	Inform systems engineers about the boundaries, terminology, and structure of their discipline and point them to useful information needed to practice SE in any application domain.
2	Inform Research	Inform researchers about the limitations and gaps in current SE knowledge that should help guide their research agenda.
3	Inform Interactors	Inform performers in interacting disciplines (system implementation, project and enterprise management, other disciplines) of the nature and value of SE.
4	Inform Curriculum Developers	Inform organizations defining the content that should be common in undergraduate and graduate programs in SE.
5	Inform Certifiers	Inform organizations certifying individuals as qualified to practice systems engineering.
6	Inform SE Staffing	Inform organizations and managers deciding which competencies that practicing systems engineers should possess in various roles ranging from apprentice to expert.

The SEBoK is a guide to the body of systems engineering knowledge, not an attempt to capture that knowledge directly. It provides references to more detailed sources of knowledge, all of which are generally available to any interested reader. No proprietary information is referenced, but not all material referenced is free—for example, some books or standards must be purchased from their publishers. The criterion for including a source is simply that the authors believed it offered the best generally available information on a particular subject.

The SEBoK is global in applicability. Although SE is practiced differently from industry to industry and country to country, the SEBoK is written to be useful to systems engineers anywhere. Authors have been chosen from diverse locales and industries, and have refined the SEBoK to broaden applicability based on extensive global reviews of several drafts.

The SEBoK aims to inform a wide variety of user communities about essential SE concepts and practices, in ways that can be tailored to different enterprises and activities while retaining greater commonality and consistency than would be possible without the SEBoK. Because the world in which SE is being applied is evolving and dynamic, the SEBoK is designed for easy, continuous updating as new sources of knowledge emerge.

Scope and Context of the SEBoK

The SEBoK is one of two complementary products. The other, which uses the content of the SEBoK to define a core Body of Knowledge to be included in graduate SE curricula, is called the Graduate Reference Curriculum in Systems Engineering (GRCSE). The GRCSE is not a standard, but a reference curriculum to be tailored and extended to meet the objectives of each university’s graduate program. These products are being developed by the Body of Knowledge and Curriculum to Advance Systems Engineering (BKCASE) project.

Most of the SEBoK (Parts 2 – 6) focuses on domain-independent information—that which is universal to systems engineering regardless of the domain in which it is applied. Part 7 includes examples from real projects. These illustrate the concepts discussed elsewhere in the SEBoK, while detailing considerations relevant to domains such as aerospace, medicine, and transportation.

SE in the context of Engineered Systems (glossary) (ES) is the primary scope for the SEBoK, though general systems concepts are also discussed in Part 2. The SEBoK also covers considerations for the disciplines of software engineering and project management, which are strongly intertwined with the practice of SE.

The context of the SEBoK is elaborated in two agent-activity-artifact diagrams in Part 1.

One summarizes the SEBoK’s definition by an international group of volunteer authors; its review by the SE community at large; its life cycle evolution management and support by the two primary international SE-related professional societies, the Institute of Electrical and Electronic Engineers (IEEE) and the International Council on Systems Engineering (INCOSE); and its use in derivative products and services by the community at large.

A second diagram summarizes the interactions among systems engineers, systems developers, and the environment of an engineered system, across its life cycle of system definition, development, evolution (production, utilization, and support) and retirement. These are further elaborated in the discussion of the nature of systems and systems engineering in Part 2, and in the Life Cycle Models article in Part 3.

Systems and Systems Engineering

Definitions of the terms “System,” “Engineered System,” “Systems Engineering,” and “Systems Engineer” were provided at the beginning of this Introduction. For the purposes of the SEBoK, the elaborated (INCOSE 2011). definition of “Systems Engineering” is modified to, “It focuses on holistically and concurrently understanding stakeholder needs; exploring opportunities; documenting requirements; and synthesizing, verifying, validating, and evolving solutions while considering the complete problem, from system concept exploration through system disposal.”

With respect to terminology, as with many special disciplines, Systems Engineering (SE) uses some terms in ways that may be unfamiliar outside the discipline. For example, in systems science, “open” means “not closed,” in terms of a system’s being able to interact with its environment. But in the area of system interface standards, “open” means “non-proprietary” or “publicly agreed upon.” And, depending on the context, the term “system” may refer to an engineered system, a natural system, a social system, or all three.

As the province of SE is engineered systems, most of the discussions assume that this is the context. Thus, “the system architecture” will refer to the architecture of the system being engineered (e.g., a spacecraft) and not the architecture of a natural system outside its boundary (e.g., the solar system). However, this may produce ambiguities at times: for example, does “management” refer to management of the SE process or management of the system being engineered? In such cases, the SEBoK tries to avoid misinterpretations by elaborating the alternatives into “system management” or “systems engineering management.”

In some cases, terms reflect the historical evolution of SE. “Soft SE” was introduced in (Checkland 1981) to emphasize the criticality of human factors in SE, an emphasis that is now accepted as an integral part of SE. Similarly, “systems architecting” was introduced in (Rechtin 1991) to emphasize that better systems resulted from approaches taken by architects to concurrently rather than sequentially address a system’s operational concept, requirements, architecture, plans, and economics, again an emphasis that is now accepted as an integral part of SE.

In other cases, terms have considerable overlap, such as “enterprise SE” and “system of systems SE.” Here and in general, the SEBoK provides an extensive Glossary to show how these terms are used in the SEBoK, and to identify how the terms may vary in different contexts. When these need further explanation, the Glossary entry includes pointers to the relevant articles providing detailed discussions. For more discussion on the definition of systems, please see the What is a System? article in Part 2; for more on systems engineering, please see Part 3.

SEBoK Uses

The diversity of communities involved with systems engineering (its various specialists, other engineers, managers, researchers, educators) means that its content will be drawn upon in several ways. The SEBoK includes several use cases, showing how these communities will use the SEBoK, and identifying the parts of the SEBoK that will be of most interest to them. These can be found in the article SEBoK Users and Uses. This discussion includes consideration of primary users – those who will directly use the SEBoK – and secondary users – those who are expected to require assistance from a systems engineer to utilize the SEBoK. For more information, please see the SEBoK Users and Uses article.

SEBoK Development

The first version of the SEBoK – a prototype labeled Version 0.25 – was released as a PDF document for limited review in September 2010. A total of 3135 comments were received on this document from 114 reviewers across 17 countries. The author team reviewed these comments, paying particular attention to the reviews related to content and highlighting diversity within the community. The second version of the SEBoK – a prototype labeled Version 0.5 – was released on September 19, 2011. This, the third version 0.75 of the SEBoK, was released on March 15, 2011.

In January 2011, the authors agreed to transition from a document-based SEBoK to a wiki-based SEBoK, with the intent to make the information readily accessible worldwide, provide additional methods for searching and navigating the content, and provide a forum for the community to offer feedback while keeping the content of the SEBoK stable between versions. For more information, please see the SEBoK Evolution article.

References

Works Cited

INCOSE. 2011. INCOSE Systems Engineering Handbook, version 3.2.1. San Diego, CA, USA: International Council on Systems Engineering (INCOSE). INCOSE-TP-2003-002-03.2.

Bertalanffy, L. von. 1968. General System Theory: Foundations, Development, Applications. Revised ed. New York, NY, USA: Braziller.

Checkland, P. 1981. Systems Thinking, Systems Practice. Hoboken, NJ, USA: Wiley (2nd edition 1999).

Gruhl, W. and Stutzke, R. 2005. “Werner Gruhl Analysis of SE Investments and NASA Overruns,” in Stutzke, R., Estimating Software-Intensive Systems. Boston, MA, USA: Addison Wesley, page 290.

Johnson, J. 2006. My Life Is Failure: 100 Things You Should Know to Be a Better Project Leader. Boston, MA, USA: Standish Group International.

Leveson, N. 2012. Engineering a Safer World: Systems Thinking Applied to Safety. Cambridge, MA, USA: MIT Press.

Rechtin, E. 1991. Systems Architecting. Upper Saddle River, NJ, USA: Prentice Hall.

Primary References

INCOSE. 2011. Systems Engineering Handbook, version 3.2.1. San Diego, CA, USA: International Council on Systems Engineering (INCOSE). INCOSE-TP-2003-002-03.2.

Sage, A., and Rouse, W. (eds.) 1999. Handbook of Systems Engineering and Management. Hoboken, NJ, USA: John Wiley and Sons, Inc.

Additional References

Bertalanffy, L. von. 1968. General System Theory: Foundations, Development, Applications. Revised ed. New York, NY, USA: Braziller.

Blanchard, B., and Fabrycky, W. 2010. Systems Engineering and Analysis, (5th edition). Saddle River, NJ, USA: Prentice Hall.

Checkland, P. 1981. Systems Thinking, Systems Practice. Hoboken, NJ, USA: Wiley (2nd edition 1999).

Booher, H. (ed.) 2003. Handbook of Human Systems Integration. Hoboken, NJ, USA: Wiley.

Hitchins, D., 2007. Systems Engineering: A 21st Century Methodology. Chichester, England: Wiley.

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SEBoK v. 1.9.1 released 30 September 2018

SEBoK Discussion

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