Preface to Designing Complex Systems: Foundations of Design in the Functional Domain

This book attempts to develop a rigorous basis for carrying out that early part of the design process that converts a set of requirements on the service to be provided by a system into requirements on a set of interacting functional elements, which then form the point of departure for the classical part of the design process - the conversion of functional requirements into a physical entity that, through its operation, will satisfy those requirements.

The reason for including this book in a series dedicated to Complex Systems, that is, a class of systems where the elements are predominantly independent agents behaving and interacting in a dynamic fashion, is that, while the systems to which the design methodology applies are not generally in this class, the environment in which the design takes place exhibits these characteristics. In the not too distant past, engineers would exclude consideration of much of this environment from their scope of work, but this narrow focus and limitation of responsibility are no longer accepted, neither by our clients nor by society. On the contrary, the increasing intrusiveness of such engineered objects as highways, railways, ports, dams, mines, and factories, just to name a few, into our daily lives and environment, coupled with a much greater awareness of the wider consequences of engineering works, has led to the demand of both clients and society for a holistic approach to the design of these objects and to a greatly increased legal regime. As a result, the complexity of the environment in which design takes place is reflected in the design process itself, and it is this complexity, rather than any complexity of the objects themselves, that systems engineering needs to address.

The immediate purpose of the book is to introduce students and practitioners in the field of system design to the basic issues raised by this complexity and to a methodology that addresses those issues in a rigorous and consistent, top-down fashion. A much more indirect purpose, and one with regard to which the book can, at best, initiate a discussion within the engineering profession, is to reassess the characteristics of engineering and its place within the field of intellectual activity, in particular, to examine the creative aspects of design, as reflected in the difference between an engineer and a technician. A central theme is the necessity for developing standardized functional elements, the building blocks of design in the functional domain and the counterpart of standardized construction elements in the physical domain. The argument for this is simple: Without standardized construction elements, such as nuts, bolts, bearings, beams, resistors, capacitors, etc., the design of physical equipment would be hopelessly inefficient, and engineers would be forever bogged down with redesigning these elements over and over again. Instead, a large part of design is now the application of these standard elements according to fixed rules, and can be carried out by technicians and design drafters, freeing the engineers for the unique and creative part of each project. Why should not the same be true in the functional domain, that is, in the domain of ideas and performance requirements, which must precede any physical realization? Only through such standardization will the significant increase in efficiency and quality, which systems engineering promises, be realized. The attitude that mental activity is spontaneous and somehow "effortless" only because it does not expend material resources must by now surely be well and truly outmoded, and all the effort that has gone into improving the efficiency of physical work, through time and motion studies and the like, now needs to be replicated for mental work. And just as machine tools increased the productivity of factory workers and CAD systems increased the productivity of drafters, new software tools can be developed to increase the productivity of system designers (as distinct from software for managing the design process).

The work reported on in this book was undertaken in the years between 1998 and 2001 and subsequently reviewed by Terje Fossnes from the Royal Norwegian Navy. The work was sporadically updated and modified as a result of other research undertaken by the author in the years since; however, the present version owes its genesis to the initiative and support of a group of engineers at MITRE, led by Brian White (as editor of the Taylor & Francis series Complex and Enterprise Systems Engineering), and, in particular, to the thought-provoking review carried out by Duane Hybertson. The support of the publisher, Rich O'Hanley, is also gratefully acknowledged.

The book is divided into three parts, each with a somewhat different view of the complexity of the design process. Part A considers the purpose and basic features of design, and how the concept of value can provide a quantitative measure of that wider interaction of the engineered object with its environment. Part B develops the domain in which functional design takes place, and explores how the system concept, as the key to handling complexity, can be embedded in that domain. Finally, Part C proposes a number of functional design elements and develops them in considerable detail, and outlines how they could be applied as part of a coherent functional design framework, supported by a software tool.

Finally, my sincere thanks go to my wife, Elfi, without whose unstinting support my systems engineering work would not be possible.

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