Chapter 1
Introduction to System Engineering
This text deals with system engineering, or the orderly process of bringing a system into being and the subsequent effective and efficient operation and support of that system throughout its projected life cycle. It constitutes an interdisciplinary approach and means for enabling the realization and the follow-on deployment of a successful system.
A system comprises a complex combination of resources (in the form of human beings, materials, equipment, hardware, software, facilities, data, information, services, etc.), integrated in such a manner as to fulfill a specified operational requirement. A system is developed to accomplish a specific function, or a series of functions, with the objective of responding to some identified need. The various elements of a system must be directly tied to and supportive in the accomplishment of some given mission scenario or series of scenarios.
A system may be classified as a natural system, human-made system, physical system, conceptual system, closed-loop system, open-loop system, static system, dynamic system, and so on. This text addresses primarily human-made systems that are physical, dynamic, and open loop in structure. Further, the objective is to address the system in the context of its whole versus dealing with its components only. Of significant importance is the realization that ultimate system performance is dependent not only on the complete and timely integration of its various components, but also on establishing the proper interrelationships among these components. By accomplishing this through the application of system engineering principles and concepts, a value-added component can be realized.
A system may vary in form, fit, and/or function. One may be dealing with a group of aircraft accomplishing a mission at a specific geographical location; a cloud-based communication network for the processing of information on a worldwide basis; a tightly integrated collection of integrated circuit chips, printed circuit boards, and higher-level modular electronics processing huge amounts of Internet and consumer mobile data for products in variety of vertical sectors; a power distribution capability involving waterways and electrical power-generating units; a healthcare capability including a group of hospitals and mobile units serving a given community; a manufacturing facility that produces x products in a designated time frame; or a small vehicle providing the transportation of certain cargo from one location to another. A system may also be contained within some overall hierarchy such as an aircraft within an airline system, which is within a larger regional transportation system, which is within a worldwide transportation capability, and so on. In this context, we may be dealing with system of systems (SOS), a popular term currently being applied in describing highly complex systems within some higher-level structure. The objective is to be able to adequately define and describe the overall boundaries of the particular system being addressed and its interfaces (and interrelationships) across the board.
A system must have a purpose! It includes not only those basic elements that are directly related to accomplishing the mission itself (configuration items, subsystems, segments, components or parts) but also those enabling elements that are necessary for keeping the system in service or ending its service, processes or products used to enable a system development, test, production, training, deployment, support, and ultimate disposal. In other words, for a system to be able to accomplish its intended mission, it must also include its total maintenance and support infrastructure.
The objectives of this chapter are: to address the subject of systems in general, to define some key terms and the characteristics of systems, to identify the need for and the basic requirements for bringing systems into being and for later evaluating systems in terms of their effectiveness in a user's environment, and to provide an introduction to system engineering and the associated management activities inherent in and supportive of the system engineering process.
1.1 Definition of a System
In order to ensure a good and common understanding of the material throughout this text, it seems appropriate to commence with a few definitions. As a start, one should first establish a basic definition for a system. Although this may appear to be overly simplistic, experience has indicated that people throughout the world tend to utilize the term rather loosely to describe many different situations and configurations. Further, there is a lack of consistency in the application of system engineering principles and concepts. Thus, it is important to first review a few terms to establish a baseline for further discussion.
1.1.1 The Characteristics of a System
The term system stems from the Greek systēma, meaning an “organized whole.” Merriam-Webster's Collegiate Dictionary defines a system as “a regularly interacting or interdependent group of items forming a unified whole.”1 One of the early Military Standards on the subject, MIL-STD-499, defines a system as “a composite of equipment, skills, and techniques capable of performing and/or supporting an operational role. A complete system includes all equipment, related facilities, material, software, services, and personnel required for its operation and support to the degree that it can be considered a self-sufficient unit in its intended environment.”2 A more recent document, EIA/IS-632, defines a system as “an integrated composite of people, products, and processes that provide a capability to satisfy a stated need or objective.”3
In the world of “semiconductor systems,” integrated chips have become so complex in both design and manufacturing that they are called, “Systems-on-Chip (SoC).” The integrated circuit in a SoC may contain digital, analog, mixed-signal, and often radio-frequency functions all on a single chip substrate. Even in the early days of the SoC, the IEEE recognized that, “the definition of the ‘system’ design and manufactured on a chip has significantly changed and expanded as did the technology, skills, tools, and methodologies required to produce it.”4
“Software systems” offer an example of the many and varied use of both the term “software” and “systems.” System software operates and controls electronic hardware to provide a platform for running application software. System software can further be separated into categories of firmware/drivers, operating systems and applications.
Given the variations in the basic definition of a “system,” the leadership of INCOSE (International Council on Systems Engineering) assigned the current Fellows of the Council to develop a consensus definition. After a few iterations, the following definition evolved:
A “system” is a construct or collection of different elements that together produce results not obtainable by the elements alone. The elements, or parts, can include people, hardware, software, facilities, policies, and documents; that is, all things required to produce system-level results. The results include system-level qualities, properties, character...