Scope of the SEBoK
The scope of the Guide to the Systems Engineering Body of Knowledge (SEBoK) can be understood in two dimensions:
- General boundaries and characteristics, based on the definition and scope of systems engineering (SE) itself
- Life cycle, based on the life cycle of SE in the context of an engineered system (ES)
SEBoK General Boundaries and Characteristics
In general, the SEBoK:
- is a guide to the body of systems engineering knowledge which provides references to detailed sources for additional information; it is not a self-contained knowledge resource
- is domain-independent, with implementation examples to provide domain-specific context
- focuses on engineered systems (ES), that is, products, services, enterprises, and systems of systems (SoS), while treating social and natural systems as relevant and important environmental considerations for ESs (see “Scope of Systems Engineering within the Systems Domain” below, and What is a System? in Part 2)
- recognizes that SE principles can be applied differently to different types of systems (see Part 4)
- explores the interaction between SE and other disciplines, highlighting what systems engineers need to know about these disciplines (see Part 6)
Each of these considerations depends upon the definition and scope of SE itself, which is the subject of the next section.
Scope of Systems Engineering within the Systems Domain
While considering all classes of systems, SE focuses on the domain of the engineered systems (ES). Sociotechnical systems are treated as a special form of engineered systems. The differences and commonalities in scope of the three overall categories of systems — engineered, natural, and social — are depicted in Figure 1 below. (The figure is one version of a diagram which one could produce many other versions. The underlined headings showing system category would always remain the same, while the bullet points listing instances of systems within and across those categories, could change with each new version.)
This picture provides a convenient tool for understanding the scope of an engineered system. For example, power generation and distribution systems are purely engineered systems which include software and human operators as well as hardware. Water and power safety legislation comes from the political processes of a legislature, which is a social system. The resulting water and power safety assurance and safety governance systems are sociotechnical systems whose participants work in both engineered systems and social systems.
The nature of and relationships between these system domains is discussed in Part 2, Systems of the SEBoK. Part 2 considers the general nature and purpose of systems and how these ideas are used to ensure better ESs. Part 2 covers
- Systems Thinking – a way of understanding complex situations by looking at them as combinations of systems.
- Systems Science – a collection of disciplines that have created useful knowledge by applying systems thinking and the scientific method to different aspects of the system domains.
- Systems Approach – a way of tackling real world problems which makes use of the tools of system science to enable useful systems to be engineered and used.
The systems approach requires understanding of both natural and sociotechnical systems to identify and scope the engineering of system problems or opportunities . It is critical to understand each of these system types if ESs are to be deployed into real world situations, achieve their assigned goals, and not adversely impact other outcomes.
The primary focus of the knowledge in Part 3, Systems Engineering and Management and Part 4, Applications of Systems Engineering is on how to create or change ESs to fulfill the goals of all relevant stakeholders within these wider system contexts. The knowledge in Part 5, Enabling Systems Engineering and Part 6, Related Disciplines includes the need for SE itself to be integrated and supported within the human activity systems in which it is performed and the relationships between SE and other engineering and management disciplines.
Scope of Systems Engineering within the Engineered Systems Domain
The scope of SE does not include the entire ES domain. Activities such as system construction, manufacturing, funding, and general management are part of the SE environment , but other than the specific management of the SE function, are not considered as part of SE. This is reflected in the International Council on Systems Engineering (INCOSE) top-level definition of systems engineering as, “an interdisciplinary approach and means to enable the realization of successful systems.” (INCOSE 2011) For example, SE can enable the realization of successful systems, but cannot ensure a successful realization if the systems’ funding, implementation, general management, and manufacturing are poorly managed and executed.
Again, a convenient way to define the scope of SE within the ES domain is to develop a Venn diagram showing the relations among SE, system implementation, and project /systems management, as shown in Figure 2. Activities, such as analyzing alternative methods for production, testing, and operations, are part of SE planning and analysis functions. Such activities as production line equipment ordering and installation, and its use in manufacturing, are still important SE environment considerations even though they are “outside” the SE boundary . Note that as defined in Figure 2, system implementation engineering also includes the software production aspects of system implementation. Software engineering, then, is not considered a subset of SE.
Traditional definitions of SE have emphasized sequential performance of SE activities, e.g., “documenting requirements , then proceeding with design synthesis …”. (INCOSE 2011) The SEBoK authors have emphasized the inevitable intertwining of system requirements definition and system design in the following revised definition of SE:
Systems Engineering (SE) is an interdisciplinary approach and means to enable the realization of successful systems. 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. (INCOSE 2011, modified)
Part 3, Systems Engineering and Management, elaborates on the definition above and offers additional definitions and constructs, providing further context for the other parts of the SEBoK.
Context of the SEBoK
SE and Engineered Systems Project Life Cycle Context
Figure 4 summarizes the main agents, activities, and artifacts involved in the life cycle of SE, in the context of a project to create and evolve an ES. For each primary project life cycle phase of system definition , system initial operational capability (IOC) development, and system evolution and retirement, it shows the activities being performed by the primary agents (the systems engineers, the systems developers, and the primary project-external bodies (users , owners, external systems) constituting the project environment, in creating the evolving states of the ES, which may be a product, service, and/or enterprise.
The semantics of the boxes and arrows in Figure 4 are that the boxes in the center three columns show activities being performed by the relevant agents in the column, while the boxes in the right-hand column are the resulting artifacts. An arrow going from box A to box B means that the successful outcome of box B depends on the successful outcome of box A. In some cases in Figure 4, there are two-way dependencies, as in the handling of the inevitable changes that arise during system development and evolution.
For example, the system’s users and owners may propose changes to respond to competitive threats or opportunities , or to adapt to changes imposed by independently evolving external systems, such as Commercial-off-the-Shelf COTS products, cloud services, or supply chain enablers. These require negotiation among these stakeholders and the system developers, in which the SEs play a key role in analyzing the relative costs and benefits of alternative change proposals, and in synthesizing mutually satisfactory solutions.
SEBoK Domain Independence Context
The SEBoK uses language and concepts that are generally accepted for domain-independent SE. For example, the domain-independent conceptual foundations of SE are elaborated in Part 2, Systems. However, each of the numerous domains in which SE is practiced — including telecommunications, finance, medicine, and aerospace — has its own specialized vocabulary and key concepts. Accordingly, the SEBoK is designed to show how its domain-independent material relates to individual domains, by means of examples that tell stories of how SE is applied in particular domains.
While the main body of the SEBoK (Parts 1 through 6) is domain-independent, an entire Part (Part 7 ) consists of examples (case studies and vignettes), each set in a particular domain such as aerospace, medicine, or software, and featuring vocabulary and concepts special to that domain. There are similar vignettes in some of the Use Cases in Part 1.
These examples demonstrate the effect of domain on the application of SE and complement the domain-independent information elsewhere in the SEBoK. They show how a concept works in a given domain and provide a fair opportunity for reviewers to reflect on whether there are better ways to capture application-dependent aspects of SE knowledge.
The authors recognize that case studies and vignettes add significant value to the SEBoK, and expect many more to be added as the SEBoK evolves.
SEBoK Life Cycle Context
Figure 3 summarizes the main agents, activities, and artifacts involved in the SEBoK life cycle. The SEBoK is one of two primary products of the Body of Knowledge and Curriculum to Advance Systems Engineering (BKCASE) Project. The other product, the Graduate Reference Curriculum in Systems Engineering (GRCSE) uses the content of the SEBoK to define a core body of knowledge (CorBoK) to be included in graduate SE curricula. 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.
The BKCASE project, led by Stevens Institute of Technology and the Naval Postgraduate School, has drawn on three primary resources. The U.S. Department of Defense (DoD) has provided the funding and includes a representative, but has not constrained or directed the project’s approach and content. The DoD Systems Engineering Research Center (SERC), a DoD university affiliated research center operated by Stevens Institute of Technology, supports BKCASE management and infrastructure and is the means by which DoD funding is delivered to the BKCASE project. The over 70 international author team members have been selected for their expertise in SE and their diversity with respect to home country (authors have come from 15 different countries), economic sector (government, industry, academia), and SE specialty area. Except for travel support in a few cases, authors have donated their time to the development of the SEBoK content.
The SEBoK content has been incrementally developed. Each of the 0.25, 0.5, and 0.75 versions has undergone an open review by all interested parties. Reviews have involved over 200 reviewers and thousands of comments each of which has been adjudicated. Upon completion of the initial SEBoK and GRCSE development in late 2012, the Institute of Electrical and Electronic Engineers Computer Society (IEEE-CS) and the International Council on Systems Engineering (INCOSE) will become the primary stewards together with the SERC for both the SEBoK and GRCSE. Interested parties should be able to undertake development, operations, and support of additional derivative products and services, such as course-ware, education, certification, and domain-specific versions of the SEBoK and GRCSE.
References
Works Cited
INCOSE. 2012. Systems Engineering Handbook, version 3.2.2. San Diego, CA, USA: International Council on Systems Engineering (INCOSE). INCOSE-TP-2003-002-03.2.
Primary References
INCOSE. 2012. Systems Engineering Handbook, version 3.2.2. San Diego, CA, USA: International Council on Systems Engineering (INCOSE). INCOSE-TP-2003-002-03.2.
Additional References
Sage, A. and W. Rouse (eds). 1999. Handbook of Systems Engineering and Management. Hoboken, NJ, USA: John Wiley and Sons, Inc.
SEBoK Discussion
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