IntroductionHeuristicsHeuristics in Systems Architecting & EngineeringHeuristics-Based Cost ModelRechtin’s System Architecting HeuristicsFour Categories of HeuristicsModel Development HeuristicsModel Calibration HeuristicsModel Usage HeuristicsEstimation HeuristicsConclusionAcknowledgementsReferencesBiographyRicardo Valerdi is a Research Associate in the Lean Advancement Initiative and a Lecturer in the Engineering Systems Division at MIT. He is also the co-founder of the Systems Engineering Advancement Research Initiative (SEAri). He received his B.S./B.A. in Electrical Engineering from the University of San Diego in 1999, and his M.S. and Ph.D. degrees in Systems Architecting and Engineering from USC in 2002 and 2005. He is the author of over 50 technical publications which have appeared in several journals, including Journal of Systems Engineering, Journal of Systems and Software, IEEE Software, International Journal of System of Systems Engineering, and CrossTalk - The Journal of Defense Software Engineering. He serves on the INCOSE Board of Directors as Treasurer.Zen in the Art of Cost EstimationRicardo ValerdiMassachusetts Institute of [email protected] © 2008 by Ricardo Valerdi. Published and used by APCOSE with permission.Abstract. Engineering cannot wait until all phenomena are explained. Engineers maywork effectively, often for centuries, with heuristics. This paper provides over thirtyheuristics that have been inspired by the development and application of a systemsengineering cost estimation model. The objective of this paper is to present such heuristics ina simple manner so that they can benefit those that develop, calibrate, and use cost models.IntroductionThis paper provides a collection of heuristics, or small nuggets of wisdom, to help systemsengineers along the road of cost estimation in the same way Zen Buddhism encourages seeingdeeply into the nature of things by direct experience. The Zen monks taught that in everymenial task there is something to be learned and something that the student can later meditateon. The Zen monks believe that one can gather knowledge from all things in life. While Zenbegan in China in the 6th century and spread to Japan, Vietnam, Korea, and eventually theWestern world, several authors have made the connection between Zen and other activitiessuch as motorcycle maintenance (Pirsig 1974), flying (Shade 1975), golf (Hebron 1990),writing (Bradbury 1992), fatherhood (Lewis 1997), comedy (Sankey 1998), flowerarrangement (Herrigel 1999), and even tennis (Koran 2002). Arguably the most popularexample is the text Zen in the Art of Archery (Herrigel 1948) which was written by Germanphilosopher Eugen Herrigel (1884–1955). Since its first German edition in 1948, the bookhas been translated into several foreign languages (English, Japanese, Portuguese, etc.) andhas been continually reprinted as one of the best-selling works on Japanese culture. As aresult, the term “Japanese archery” evokes thoughts of spiritual training and Zen spirituality(Yamada 2001).HeuristicsA heuristic is a method to help solve a problem, commonly informal. It is particularly usedfor a method that often rapidly leads to a solution that is usually reasonably close to the bestpossible answer. Heuristics are "rules of thumb", educated guesses, intuitivejudgments or simply common sense. In more precise terms, heuristics stand for strategiesusing readily accessible, though loosely applicable, information to control problem-solving inhuman beings and machines. Heuristics are common in psychology, philosophy, law, andengineering. A commonly used heuristic is:If you are having difficulty understanding a problem, try drawing a picture.In psychology, heuristics are simple, efficient rules, hard-coded by evolutionaryprocesses. Heuristics have been proposed to explain how people make decisions, come tojudgments, and solve problems, typically when facing complex problems or incompleteinformation. These rules work well under most circumstances, but in certain cases lead tosystematic cognitive biases. Because heuristics are fallible, it is important tounderstand their limitations. They are only intended to be used as aids in order to make quickestimates and preliminary process designs. Their applicability is also limited by the contextunder which they were derived.Heuristics in Systems Architecting & EngineeringIn engineering, a heuristic is an experience-based method that can be used as an aid tosolve specific problems (Endres & Rombach 2003). By using heuristics, time can be reducedwhen solving problems, which may be very valuable. While heuristics are not alwaysscientifically validated, they represent many years of empirical observations of experiencedprofessionals packaged in the form of concise wisdom.One area of engineering that has benefitted from heuristics is the field of systemsarchitecting as a result of Eb Rechtin’s (1926–2006) book Systems Architecting: Creating andBuilding Complex Systems (Rechtin 1991). The book contains a spectrum of more than 100heuristics that provide insights in the areas of systems architecting, development, testing, andorganizations which were derived from Rechtin’s 40 year career at NASA/Jet PropulsionLaboratory, Defense Advanced Research Projects Agency, the Department of Defense, theAerospace Corporation, and Hewlett-Packard. An example heuristic provided by Rechtin is:Don’t assume that the original statement of the problem is necessarily the best, or eventhe right one.This heuristic suggests the need for deeper analysis of solutions. It works well whenproblem and solution are not too far apart, that is, when a few leaps of imagination may bringproblem and solution together.Heuristics-Based Cost ModelCOSYSMO (the Constructive Systems Engineering Cost Model) is a parametric modelthat was developed for the purpose of estimating the cost of systems engineering effort inlarge complex systems. The model enables the estimation of systems engineering effortthrough an assessment of system characteristics such as:- Number of System Requirements- Number of System Interfaces- Number of System-Specific Algorithms- Number of Operational ScenariosAdditionally, the systems engineering aspect of projects