System of systems

System-of-Systems is a relatively new term that is being applied primarily to government projects for addressing large scale inter-disciplinary problems with multiple, heterogeneous, distributed systems that are embedded in networks at multiple levels and multiple domains. From an understanding and application reference, System-of-Systems development is in its infancy; many definitions and approaches are being formulated to solve these types of problems. While particular views vary, it is widely agreed that System-of-Systems is a new and critical discipline for which frames of reference, thought processes, quantitative analysis, tools and design methods for these problems are incomplete [1]. More and more often, the developing processes for addressing System-of-Systems problems are being described as System-of-Systems Engineering.

Commonly proposed descriptions, not necessarily definitions, of System-of-Systems are outlined below, collected partly from [2], and listed in order of appearance in the literature:

1) Description: Linking systems into joint System-of-Systems allows for the interoperability and synergism of Command, Control, Computers, Communications, and Information (C4I) and Intelligence, Surveillance and Reconnaissance (ISR) Systems

Applications: Information superiority in modern military

Source: Manthorpe Jr., W.H., "The Emerging Joint System-of-Systems: A Systems Engineering Challenge and Opportunity for APL," John Hopkins APL Technical Digest, Vol. 17, No. 3 (1996), pp. 305–310. [3]

2) Description: System-of-Systems are large-scale concurrent and distributed systems the components of which are complex systems themselves

Applications: Communicating structures & information systems in private enterprise

Source: Kotov, V. "Systems-of-Systems as Communicating Structures," Hewlett Packard Computer Systems Laboratory Paper HPL-97-124, (1997), pp. 1–15. [4]

3) Description: System-of-Systems Education involves the integration of systems into System-of-Systems that ultimately contribute to evolution of the social infrastructure

Applications: Education of engineers on the importance of systems and their integration

Source: Luskasik, S.J. "Systems, Systems-of-Systems, and the Education of Engineers," Artificial Intelligence for Engineering Design, Analysis, and Manufacturing, Vol. 12, No. 1 (1998), pp. 55-60.

4) Description: System-of-Systems Integration is a method to pursue development, integration, interoperability, and optimization of systems to enhance performance in future battlefield scenarios

Applications: Information intensive systems integration in the military

Source: Pei, R.S., "Systems-of-Systems Integration (SoSI) – A Smart Way of Acquiring Army C4I2WS Systems," Proceedings of the Summer Computer Simulation Conference, (2000), pp. 574–579.

5) Description: Modern systems that comprise System-of-Systems problems are not monolithic, rather year have five common characteristics: operational independence of the individual systems, managerial independence of the systems, geographical distribution, emergent behavior and evolutionary development

Application: Evolutionary acquisition of complex adaptive systems in the military

Source: Sage, A.P., and C.D. Cuppan. “On the Systems Engineering and Management of Systems-of-Systems and Federations of Systems,” Information, Knowledge, Systems Management, Vol. 2, No. 4, 2001, pp. 325–45.

6) Description: Enterprise Systems-of-Systems Engineering is focused on coupling traditional systems engineering activities with enterprise activities of strategic planning and investment analysis

Applications: Information intensive systems in private enterprise

Source: Carlock, P.G., and R.E. Fenton. "System-of-Systems (SoS) Enterprise Systems for Information-Intensive Organizations," Systems Engineering, Vol. 4, No. 4 (2001), pp. 242–261.

7) Description: System-of-Systems problems are a collection of trans-domain networks of heterogeneous systems that are likely to exhibit operational and managerial independence, geographical distribution, and emergent and evolutionary behaviors that would not be apparent if the systems and their interactions are modeled separately

Applications: National Transportation System, Integrated Military and Space Exploration

Sources: DeLaurentis, D. “Understanding Transportation as a System-of-Systems Design Problem,” 43rd AIAA Aerospace Sciences Meeting, Reno, Nevada, Jan. 10-13, 2005. AIAA-2005-0123. [5] DeLaurentis, D. A. and Callaway, R. K. “A System-of Systems Perspective for Future Public Policy,” Review of Policy Research, Vol. 21, No. 6, 2004. pp. 829–837. [6*]

From the study of these of these descriptions, it has been inferred that a complete systems framework, such as System-of-Systems, is needed to enable the decision makers to determine whether related infrastructure, policy and/or technology considerations together are good, bad or neutral over time [6*]. The need to solve System-of-Systems problems is urgent not only because of the growing complexity of today’s grand challenges, but also because System-of-Systems problems involve decisions that commit large amounts of money and resources, for which ultimate outcome carries long-term consequences for a majority of the public population.

While the individual systems that comprise System-of-Systems problems can be very different and operate independently, when working together, important emergent properties can be exposed and delivered by System-of-Systems. Stakeholders for these problems must recognize, analyze and understand the evolving nature of these emergent patterns. System-of-Systems approach does not advocate certain tools, methods or practices; instead, it seeks to promote a new way of thinking for solving grand challenges where the interactions of technology, policy and economics are the primary drivers in using this approach. System-of-Systems study is related to general study of architecting, complexity and systems engineering, but brings the additional challenge of design to the forefront.

While System-of-Systems is likely to exhibit the behaviors of complex systems, not all complex problems fall in the realm of System-of-Systems. In order to identify System-of-Systems problems, several combination of traits are inherent to these problems; a System-of-Systems problem does not need have all of these traits, but it will clearly exhibit a majority of them [7*]:

• Operational Independence of Elements
• Managerial Independence of Elements
• Evolutionary Development
• Emergent Behavior
• Geographical Distribution
• Inter-disciplinary
• Heterogeneity of Systems
• System of Networks

The first five traits are commonly known as Maier’s Criteria for System-of-System problems, while the last three have emerged from further investigation and analysis of literature and application into this field, at Purdue’s Signature area of System-of-Systems [8].

Current pursuit of providing effective approaches to System-of-Systems problems includes, but is not limited to:

• Establishment of an effective frame of reference
• Crafting of a common SoS lexicon
• Study of Architecting
• Study of various modeling & simulation techniques
  • network theory
  • general systems theory
  • probabilistic robust design (including uncertainty modeling/management)
  • agent-based modeling
  • object oriented simulation
• Study of various numerical and visual tools for capturing the interaction of system requirements, concepts, and technologies

Applications

System-of-Systems, while still predominantly applied to the defense sector, is beginning to be applied to other challenges; some specific applications that are being explored are in the Transportation System and Space Exploration. Other applications where System-of-Systems approach can be applied in are Healthcare, Internet Design, Software integration and many other national and global challenges.

Educational institutions & industry

Industry and university collaboration is helping to drive System-of-Systems development; System-of-Systems projects are taking place at several different university institutions, industry corporations and government agencies. Some of the universities that are performing research work on System-of-Systems problems are Purdue University, University of Kansas, Georgia Institute of Technology, Old Dominion University, George Mason University, University of New Mexico and Massachusetts Institute of Technology. Some of the corporations that are performing research work on System-of-Systems problems are BAE Systems, Northrop Grumman, Boeing, Raytheon and Lockheed Martin. The Federal Aviation Administration and Department of Defense are a couple of government institutions that are performing research work on System-of-Systems. For exampe: recently, National Centers for System-of-Systems Engineeringhas been established with the objective to develop a formal System-of-Systems (SoS) Engineering methodology, and to apply this methodology to Department of Defense (DoD) programs.

Selected external links & references

• Crossley, W.A. "System-of-Systems: An Introduction of Purdue University Schools of Engineering's Signature Area." [9]

• Bar-Yam, Y. and others. “The Characteristics and Emerging Behaviors of System-of-Systems.” NECSI: Complex Physical, Biological and Social Systems Project. January 7, 2004. [10]

• J. Lewe, D. DeLaurentis, D. Mavris, "Foundation for Study of Future Transportation Systems Through Agent-Based Simulation," Proceedings of 24th International Congress of the Aeronautical Sciences (ICAS), Yokohama, Japan, August 2004. Session 8.1. [11]

• Popper, S., Bankes, S., Callaway, R., and DeLaurentis, D. “System-of-Systems Symposium: Report on a Summer Conversation.” July 21–22, 2004. Potomac Institute for Policy Studies, Arlington, VA. [12]

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