Chapter 2

Emergence and Complexity of Systems of Systems 1


2.1. Introduction

The expression “system of systems” is, without a doubt, currently rather fashionable. Thus, 62,400 references could be found on the Internet in January 2006 compared to 14,000 a year before (January 2005), and by July 2007, there were no less than 402,000 references. A trend does not however hold the power to transform an expression into a concept, no matter how suggestive it may be. The concept should first have a meaning, and references. It should also be relevant, which means that, within a theory, it should help bring unity where only diversity could be perceived, or on the contrary, difference where there was only unity.

In an article published in 2001, A. Sage and C. Cuppan [SAG 01] defined a system of systems as a system displaying at least three of the following five characteristics: (1) operational independence of elements, (2) managerial independence of elements, (3) geographical distribution, (4) emergent behavior and (5) evolutionary development. The shape of this definition (three criteria among the five quoted above), wholly in keeping with the definition offered by M. Maier in “Architecting principles for systems of systems” [MAI 98], based on observation alone, is hesitant about the relevance of the selected criteria and does not provide any explanatory schema, something which makes it characteristic of stammering theorizing.

Indeed, what kind of community could have two systems of systems, ...

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