Engineering complex systems: implications for research in systems engineering

(New York:Wiley, 1999), I get many questions about systems engineering, namely, what this field includes and excludes. A quick answer is, " take a look at the handbook. " A bit more of an elaborate answer, especially if people are interested in what we are doing at Georgia Tech, can be cast in terms of the manufacturing, logistics, transportation, and health systems programs available at ISyE. This answer might also include mention of ISyE's cross-cutting areas of optimization, stochastics, statistics, economics, and human systems. These types of answers often work, but occasionally people ask aboutthefundamentalnatureof " systemsengineering, " including why, or if, this construct does not cover everything and, hence, nothing. This is a great question and in this brief note, I attempt to provide an answer. I admit on the outset, however, that this note provides plenty of opportunities for disagreement, especially among advocates of one or more of the points of view elaborated. To begin, it seems reasonable to assert that systems engineering involves the engineering of complex systems. This emphasizes engineering as a verb, i.e., something one does. Engineering as a verb implies the creation of entities that are more than just sums of parts. Creation in this manner requires analysis and synthesis of complex systems. • By system, I mean a group or combination of interrelated, interdependent, or interacting elements that form a collective entity. Elements may include physical, behavioral, or symbolic entities. Elements may interact physically, mathematically , and/or by exchange of information. Systems tend to have purposes, although in some cases the observer ascribes such purposes. • By complex systems, I mean systems whose perceived complicated behaviors can be attributed to one or more of the following characteristics: large numbers of elements, large numbers of relationships among elements, nonlinear and discontinuous relationships, and uncertain characteristics of elements and relationships. I include the idea of perceived complexity because apparent complexity can decrease with learning. Based on my perusal of a wide range of literature, as well as many discussions with colleagues at Georgia Tech and else-where—see acknowledgment—it is clear that there are several views on what " analysis and synthesis of complex systems " actually implies. In particular, there are multiple perspectives on the source of the " complexity " of the systems we are seeking to engineer. I hasten to note that a primary differentiator among these views concerns systems science vs. systems engineering. …