Complexity Reduction: A Pragmatic Approach Joseph Simpson and Mary Simpson* System Concepts, LLC, 6400 32nd Avenue N.W., #9, Seattle, WA 98107 COMPLEXITY REDUCTION: A PRAGMATIC APPROACH Received February 7, 2010; Accepted April 19, 2010, after one or more revisions Published online 3 June 2010 in Wiley Online Library (wileyonlinelibrary.com) DOI 10.1002/sys.20170 ABSTRACT An increasing need for shared communication in disparate domains as well as the production of increas- ingly dynamic, large-scale systems has always been at the heart of the practice of systems engineering. As a branch of general systems theory, systems engineering was developed to address practical consid- erations posed by diverse organizations, environments, and cultures within which systems are designed, developed, and operated. Types and categories of complexity are used in this paper to focus the discussion on complexity and the reduction of complexity. Formal and theoretical foundations of systems science and systems engineering provided the basis upon which many effective systems engineering tools were built. This paper identifies some of the classical tools of systems science and systems engineering that manage complexity. Based on these classical tool components and principles, abstract relation types (ART) were developed to enhance the understanding and application of these tools. A pragmatic approach that is designed to reduce complexity as well as compare relative complexity reduction between and among methods is also presented. The direct value of systems engineering techniques as they are applied in any context is rooted in the ability of systems engineering techniques and systems engineering practitioners to reduce the cognitive complexity associated with the systems problem of interest. © 2010 Wiley Periodicals, Inc. Syst Eng 14: 180–192, 2011 Key words: cognitive complexity reduction; abstract relation types; N-squared charts; design structure matrices 1. INTRODUCTION Systems engineering was developed to specifically address problems of complexity found in the environment, systems design, deployment, and operations. Systems engineering uses engineering technology teams and team leaders to effec- tively design, develop, and deploy large-scale systems. For- mal concepts and theoretical foundations of systems engineering were developed by many thought leaders in systems science and engineering. Key fundamentals for com- plex systems engineering analysis, design, development, and operation include the Language for a Generic Design Sci- ence; the Law of Triadic Compatibility with its Principle of Division by Threes, and the Law of Gradation and its three corollaries: the Corollary of Congruence, the Corollary of Diminishing Returns, and the Corollary of Restricted Virtual Worlds [Warfield, 1990, 1994]. Though there are other fun- damentals, these particular formal and theoretical aspects of complex systems, systems science, and engineering form the bases for a number of practical systems engineering tools and analysis approaches, and will be explored in this paper. Spe- cific classical systems engineering techniques and ap- proaches addressed in this paper are N Squared Charts (N2C) [Lano, 1979], Automated N Squared Charts (AN2C) [Hitchins, 1992], Design Structure Matrix (DSM) methods [Steward, 1981], and the Interpretative Structural Modeling *Author to whom all correspondence should be addressed (e-mail: mjs- sbw@eskimo.com; jjs-sbw@eskimo.com). Systems Engineering Vol. 14, No. 2, 2011 © 2010 Wiley Periodicals, Inc. 180 Regular Paper