Systems engineering

The International Council on Systems Engineering (INCOSE) defines system engineering as a transdisciplinary and integrative approach to enable the successful realization, use, and retirement of engineered systems, using systems principles and concepts and scientific, technological, and management methods. Systems engineering uses knowledge and techniques from various branches of engineering and science to introduce technological innovations into planning and development stages of a system.

This is not so much a branch of knowledge, but branches of engineering and disciplines of science combined to solve multifaceted engineering problems. It is related to operations research but differs in that it is more a planning and design function, frequently involving technical innovation. One of the more important aspects of systems engineering is its application to the development of new technological possibilities with the specific objective of putting them to use as economic and technical considerations permit.

Systems engineering provides facilitation, guidance, and leadership to integrate the relevant disciplines and specialty groups into a cohesive effort, forming a structured development process that proceeds from concept to production, operation, evolution, and eventual disposal. And with this, systems engineering tends to focus on:

• Establishing, balancing, and integrating stakeholder goals, purpose, and success criteria
• Defining actual or anticipated customer needs, operational concept, and required functionality, starting early in the development cycle
• Establishing an appropriate life cycle model, process approach, and governance structures, while considering the levels of complexity, uncertainty, change, and variety
• Generating and evaluating alternative solution concepts and architectures
• Baselining and modeling requirements and selected solution architecture for each phase of the endeavor
• Performing design synthesis and system verification and validation
• Considering both the problem and solutions domains and, at the same time, taking into account necessary enabling systems and services, identifying the role that the parts and the relationships between the parts play with respect to the overall behavior and performance of the system, and determining how to balance these factors to achieve a satisfactory outcome

In systems engineering, the term "system" may mean a collection of technical, natural, or social elements or a combination of all three. And, in systems science, and therefore systems engineering, there are other terms that may have different meanings, such that an "open" system refers to a system able to interact with an environment rather than a system that is non-proprietary. Other such definitions specific to systems engineering include:

• An engineered system, which is a technical or socio-technical system that is the subject of a system's engineering life cycle. It is a system designed or adapted to interact with an anticipated operational environment to achieve one or more intended purposes while complying with applicable constraints.
• An engineered system context centers around an engineered system but also includes its relationship to other engineered, social, or natural systems in one or more defined environments.

Systems engineering seeks a safe and balanced design in the face of opposing interests and multiple, often sometimes conflicting, constraints. The systems engineer should develop the skill for identifying and focusing efforts on assessments to optimize the overall design and not favor one system or subsystem at the expense of another while validating the goals of the operational system will be met. Personnel with these skills are usually tagged as system engineers.

The exact role and responsibility of the systems engineer may change from project to project, depending on the size and complexity of the project and from phase-to-phase of the life cycle. For large projects, there may be one or more systems engineers. For small projects, the project manager may sometimes perform these practices. The actual assignment of the roles and responsibilities of the named systems engineer may also vary. However, in general, the systems engineer oversees a project's system engineering activities as performed by technical team and directs, communicates, monitors, and coordinates tasks. This includes reviewing and evaluating the technical aspects of the projects to ensure that the systems and subsystems engineering processes are functioning properly and evolves the system from concept to product.

Systems engineering is normally defined and shaped by the context or environment in which it is embedded. The classical systems engineering approach is tailored to and works best in situations in which all relevant systems engineering factors are largely under the control of or can at least be well-understood and accommodated by the systems engineering organization or the program manager. Or, this is when system requirements are relatively well-established, technologies are mature, there is a single or relatively homogenous user community for whom the system is being developed, and a single individual has management and funding authority of a program.

With an increased emphasis on capabilities and networking, there is an increased recognition for the importance of effective end-to-end performance of system of systems (SoS) to meet user needs. While most government acquisition policies and processes continue to focus on the development and evolution of individual systems, their requirements are increasingly based on assessments of gaps in user capabilities that require integration across individual systems to be enabled. The role of system engineering is turning to the engineering of SoS to provide these capabilities.

A definition of system of systems and how it can be differentiated from a constituent system:

• The system of systems is a set of systems or system elements that interact to provide a unique capability that none of the constituent systems can accomplish on its own
• Whereas the constituent system is part of one or more SoS. Each constituent system is a useful system in itself, often having its own development and management goals and resources.

The increased attention on SoS has been focused on how to apply system engineering principles and practices to SoS, considering the differences between systems and SoS. Despite the recognition of SoS consideration, the focus of investment and development has largely been on individual systems. The type of systems of systems include virtual, collaborative, acknowledged, and directed system of systems.

The taxonomy of SoS is based on the degree of independence of constituents and it offers a framework for understanding SoS based on the origin of SoS objectives and the relationships among the stakeholders for both the SoS and constituent systems. Many SoS exist in an unrecognized state. And as the levels of interconnectivity between systems increases, this becomes increasingly true. Such systems can be described as "accidental" or "discovered" because only when they become significant are they recognized and, in turn, fall into one of the above four categories.

From the perspective of SoS engineers, another potential classification could consider the level of anticipation or preparation of an SoS with respect to operations and stability of the SoS objectives. This could include an SoS which responds to a particular trigger, or an SoS developed to answer ongoing needs.

Example of a systems engineering life cycle for a system of systems.

Both individual systems and SoS are considered "systems" because each consists of parts, relationships, and a "whole" greater than the sum of those parts. But not all systems are SoS. Rather, an SoS may deliver capabilities by combining multiple collaborative, anonymous-yet-interacting systems and the mix of systems may include existing, partially developed or yet-to-be-designed independent systems. And in a SoS, systems engineering deals with the planning, analyzing, organizing, and integrating of the capabilities of a mix of existing and new development systems into an SoS capability greater than the sum of the capabilities of constituent parts.

System of systems engineering (SoSE) is a set of processes, tool, and methods for designing, redesigning, and deploying solutions to system-of-systems and related challenges. SoSE has seen heavy use in the United States Department of Defense, and has also seen increased adoption and application in non-defense related problems.

SoSE is more than systems engineering, which tends to focus on monolithic complex systems, while design for system of systems problems is performed often under a level of uncertainty in the requirements of constituent systems and requires considerations in multiple levels and domains. With the increase of SoS and, therefore, the increase in SoSE outside of the defense environment, the concepts and principles are finding uses in governmental, civil, and commercial domains.

With the increase in networking and interconnectedness of systems, there is a similar growth in the number and domains where SoS and, subsequently, SoSE are becoming the norm. This is particularly with the convergence among systems of system, cyber-physical systems, and the internet of things.

Example of life cycle stages.

Systems engineering models and processes usually organize around the concept of a "life cycle". Similar to the definition of systems engineering, the conceptualization of life cycle is not unique. Examples of life-cycle stages include concept, development, production, utilization, support, and retirement. The US Department of Defense, in a variation on the theme, uses the phases of materiel solution analysis, technology development, engineering and manufacturing development, production and deployment, and operations and support.

The life cycle model is a key concept in system engineering. A life cycle for a system generally consists of a series of stages, such as those above, which are regulated by a set of management decisions that confirm the system is mature enough to leave one stage and enter the subsequent stage.

The generic life cycle model is a single-step approach that proceeds through the stages of a system's life cycle in a simple, precendential, or follow-on manner in which only one phase in the definition stage is necessary. Whereas, with build-upon systems, a lot of the systems development may occur during the definition stage. System integration, verification, and validation may follow implementation or acquisition of the system elements. With software—particularly test-first and daily builds—integration, verification, and validation are interwoven with element implementation.

The breadth of potential life cycle process models fall into three major categories:

Comparison of life cycles based on industry or organization.

1. Pre-specified and sequential processes (for example, a single-step waterfall model)
2. Evolutionary and concurrent processes (for example, lean development, the rational unified process, and forms of the vee and spiral models)
3. Interpersonal and emergent processes (for example, agile development, scrum, extreme programming, dynamic system development method, and innovation-based processes)

Regardless of the model employed, the role of the systems engineer encompasses the entire life cycle of the system. The system engineers orchestrate the development and evolution of a solution, from defining requirement through operation until system retirement. And, while systems engineering tasks are usually concentrated at the beginning of the life cycle, there is an increased recognition of the need for systems engineering throughout the system's life cycle.

As mentioned previously, systems engineering has seen wider adoption and employment from the defense industry where systems engineering is used to deliver products within cost, schedule, and scope, especially where the increased complexity of defense systems complicates the process of reaching such project targets.

In the United States, the Department of Defense (DoD) began using systems engineering methodology during World War II. After the war, the research institution RAND was created to connect military planning with research and development decisions. Over the next decades, RAND used system-based principles to develop strategic recommendations for aircraft, weapon, and ship capabilities, and military basing locations, and to determine how best to implement an air defense campaign.

Example of the increasing complexity of systems in the military.

These systems saw continued use from the DoD in order to develop a missile-defense system as part of the effort to stem Cold War aggression from the USSR. And as technology continues to advance, the DoD has evolved from procuring standalone systems to procuring complex and integrated systems of systems. Tanks, ships, aircraft, satellites, and ground stations are collecting, processing, and disseminating real-time information to ensure military decision-makers receive the best data as quickly as possible. The requirements of such systems have reinforced the need for a disciplined approach to both systems engineering and project management as an increasing number of stakeholders across a range of domains must be served.

As these capabilities and systems have continued to be used, the delineation between capability engineering, system of systems engineering, and systems engineering is defined by a hand-shake interaction, such that traditional silo-performed hand-over process interaction is no longer effective in a system of systems environment as the increasing complexity and emerging properties of integrated systems require or necessitate increased cooperation and joint capability employment.

Even though the earliest adoption of systems engineering and related methodologies came in the defense industry, the term and those methodologies have been traced back to Bell Telephone Laboratories in the 1940s, where the need to identify and manipulate the properties of a system as a whole emerged.

This came, in part, as the development of various engineering disciplines in the 19th and 20th centuries saw considerable overlap among the different fields. For example, chemical engineering and mechanical engineering were both concerned with heat transfer and fluid flow. Proliferation of specializations, such as the proliferation of electrical engineering (with communications theory, cybernetics, and computer theory, as a few specializations) has led to further overlapping. And further overlapping has resulted in systems engineering as a logical last step.

In 1990, a professional society for systems engineering, the National Council on Systems Engineering (NCOSE), was founded by representatives of a number of United States-based corporations and organizations. The society was founded to address the need for improvements in systems engineering practices and education. With a growth of involvement from international systems engineers, the name of the organization was changed to International Council on Systems Engineering (INCOSE) in 1995. Subsequently, schools in several countries began to offer graduate programs in systems engineering.

Systems engineers frequently have an electronics or communications background and often make extensive use of computers and communications technology. However, in the nature of systems engineering and the nature of the problems systems engineering addresses, it is interdisciplinary and a procedure for using separate techniques and bodies of knowledge to achieve a prescribed goal.