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Network Science 1 Introduction Network effects are found in biologically diverse worlds, at many layers of abstraction from micro to macro. These include molecular biochemical reactions, cellular neural networks, insect swarms, and entire ecologies. They also are found in such diverse engineered systems as power grids, communications networks, like the Internet, and the transportation infrastructure. Network effects are, however, most commonly associated with human social structures—we speak about networking as an essential skill for both doing our jobs and getting new ones. This dimension of networks has taken on special significance in the past few years as we recognize the powerful influence on society of criminal and terrorist social networks that exploit modern communication and transportation networks (Arquilla and Ronfeldt, 2001). In the military, network effects occur in the communication systems that link platforms and Soldiers. The concept of network-centric warfare (NCW) takes the importance of networks for the military even further. In this concept dynamic battlefield command and control networks are built in real time, relying on more static networks such as physical communications, weapons systems platforms, and military organizational structure. The differences between static and dynamic networks are, however, not clearly understood, and our understanding of dynamic network effects is primitive. Networks also build upon each other in layers—for example, a network of business process applications is built on a communications network that is, in turn, built on a physical network. Despite the tremendous variety of complex networks in the natural, physical, and social worlds, little is known scientifically about the common rules that underlie all networks. This is even truer for interacting networks. Ideas put forth by scientists, technologists, and researchers in a wide variety of fields have been coalescing over the past decade, creating a new field of thinking—the science of networks (see Box 1-1). Does a science of networks exist? Opinions differ. But if it does, network science is in its infancy and still needs to demonstrate its soundness as a science on which to base useful applications. The purposes of this report are to assess the scope and content of network science and to envision how its pursuit can create value for the United States in general and for the U.S. Army in particular. Semantics aside, the opportunity is historic. The unrelenting drop in the costs of computing, symbolized by Moore’s law, has made massive computation a commodity, cheap and available to industry and individuals alike (Rheingold, 2002). The benefits of connectivity—as quantified, for instance, by Metcalfe’s law and first recognized in the rail and telephone networks—make it irresistibly attractive (Rheingold, 2002). The value of community—asserted, for example, in Reed’s law—elevates connectivity to an economic imperative (Rheingold, 2002). The linkage of information networks has led to a global information grid, to which the majority of the world’s population is likely to be connected within the next decade. This situation is unparalleled in human history. It will lead to social institutions and human behaviors never before seen or anticipated (Ronfeldt, 2005). Its initial consequences already are being reported in the popular press (Business Week, 2005). It renders the study of networks and their effects—the pursuit of network science—a social, scientific, and technological imperative for the 21st century. Why should the military in general and the Army in particular care? Aside from the fact that the U.S. military is embedded in this wave of technological and social change, the exploration of network science promises insights and tools that are indispensable to improving its combat effectiveness in the new world of likely conflicts. The development of the Army’s Future Combat Systems (FCS) is experiencing cost and schedule overruns because of the immense complexity of the effort (Weiner, 2005). Given the committee’s findings about the immaturity of network science, this is hardly surprising. Designing and testing the FCS communications network alone is like trying to design and test a modern jet aircraft without the benefit of the science of aerodynamics or like designing and testing a radio or
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Network Science BOX 1-1 Network Science: Foundation of Our Connected Age The first thing you see in the room on your right as you enter Boston’s Museum of Science is a vertical peg board about 8 feet square. Sticking out of a checkerboard square pattern are pegs at the corner of every square. Ping-pong-size balls drop from the center top of the board and carom crazily off various pegs on the way down to the bottom. There is no way to predict which way a ball will zig or zag at each row or where any one ball will land in the bottom row. The pathway of each drop is completely random. Yet, despite the chaos at the beginning, the balls collect at the bottom in a perfect normal curve distribution. Within moments, the system changes from totally random individual actions to a completely symmetrical and predictable aggregate—order emerges out of chaos. Similar phenomena are exhibited by human social networks, like the complex web of traders and investors on the New York Stock Exchange (Bernstein, 1992) or the operation of any large city (Johnson, 2001; Watts, 2003). Why? Such is the mystery of self-organization in large, complex networks. Similarly, what accounts for how birds flock and fish school? Why do accumulated grains of sand build to a mound or dune until finally one grain proves to be a grain too many and an avalanche occurs? And why do electrical systems crash when they reach comparable tipping points? Why are we all connected by the famous six degrees of separation? What do epidemics, earthquakes, computer viruses, religious fundamentalism, and the “Friends of Kevin Bacon” game all have in common? The common element in the answers to these questions is that things are connected. Connections create networks, networks operate by rules and probably laws, and a new science of networks is emerging to determine and explain what these are. Nations, species, corporations, and armies will all be affected by this new science. TV without the benefit of the fundamental knowledge of electromagnetic waves. The engineering of complex physical networks, like that of the FCS, is not predictable because the scientific basis for constructing and evaluating such designs is immature. This is even more the case for characterizing, modeling, and evaluating modern criminal and terrorist networks that are built on a physical communications network infrastructure (Arquilla and Ronfeldt, 2001). The Office of Force Transformation (OFT) has advanced the concepts of network-centric warfare (Cebrowski and Garstka, 1998) and network-centric operations (Garstka and Alberts, 2004) to define warfare in the 21st century. Both concepts involve multiple interacting networks built one on top of the other. Neither has a firm empirical and analytical base. Thus, getting a grip on the fundamental science of networks—their structure and dynamics—is a topic of pressing concern for military as well as political and economic interests. SCOPE OF THE STUDY Recognizing the urgency of this situation, the National Research Council (NRC) Board on Army Science and Technology (BAST) formed the Committee on Network Science for Future Army Applications. The statement of task for the committee consists of four charges (Box 1-2). This document is the report of that committee. STUDY APPROACH AND CONSTRAINTS Special care was devoted to the composition of the committee. Biographies are given in Appendix A. Three representative groups of members were selected. The first group included individuals from the physical sciences, engineering, biological sciences, and social sciences research communities. In order to sample the breadth of intellectual effort on network science, committee members were selected who have recent first-hand experience in the subject matter as reflected in their recent books or research and teaching assignments. Thus, committee membership includes the authors of Six Degrees: The Science of the Connected Age BOX 1-2 Statement of Task The Assistant Secretary of the Army (Acquisition, Logistics, and Technology) has requested the National Research Council (NRC) Board on Army Science and Technology (BAST) conduct a study to define the field of Network Science. The NRC will: Determine whether initiation of a new field of investigation called Network Science would be appropriate to advance knowledge of complex systems and processes that exhibit network behaviors. If yes, how should it be defined? Identify the fields that should comprise Network Science. What are the key research challenges necessary to enable progress in Network Science? Identify specific research issues and the theoretical, experimental, and practical challenges to advance the field of Network Science. Consider such things as facilities and equipment that might be needed. Determine investment priority, time frame for realization, and degree of commercial interest. Given limited resources (and likely investments of others), recommend those relevant research areas that the Army should invest in to enable progress toward achieving Network-Centric Warfare capabilities.
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Network Science (Duncan Watts); Linked: The New Science of Networks (Albert-Laszlo Barabási); The Future of Work (Thomas Malone); and It’s Alive: The Coming Convergence of Information, Biology and Business (Stan Davis); and the editor of Control in an Information Rich World: Report of the Panel on Future Directions in Control, Dynamics and Systems (Richard M. Murray), a report of the Society for Industrial and Applied Mathematics (SIAM). The committee also includes the organizer of the new systems biology curriculum at Harvard University (Pamela A. Silver) and a contributor to the World Technology Evaluation Center’s assessment of systems biology (Adam Arkin). Thus, active players in the diverse communities engaged in creating the science of modern networks are represented on the committee. The second representative group comprises both the command and the research and development (R&D) communities of the military, including retired flag officers and experts with experience at the Defense Advanced Research Projects Agency (DARPA) (Ronald J. Brachman), the National Defense University (Robert E. Armstrong), and MITRE (Norval L. Broome). Paul Van Riper, who first applied the concepts of network science to the articulation of the command-and-control doctrine in the U.S. Marine Corps, is among the flag officers, as are William Hilsman, former chief information officer of the Army and Jack Pellicci, a retired Army brigadier general who is now an executive for the Oracle Corporation. The third group includes representatives from the academic and industrial management worlds. Two deans (Richard DeMillo, Georgia Institute of Technology, and John E. Hopcroft, Cornell) played a major role in defining the scope of the study. Dr. DeMillo also has served as chief technology officer of Hewlett-Packard. The committee’s outreach efforts were led by Richard Murray (California Institute of Technology) and by Will E. Leland, chief scientist, Telcordia Technologies. The committee chair Charles Duke, has been an R&D manager for 22 years at Xerox and was chief scientist and deputy director of the Pacific Northwest National Laboratory. Clearly, the committee membership spans the diverse constituencies of network science: military commanders, business managers, program managers, research managers, and active researchers. Together, the members had the skills and experience needed to assess the content of network science; its prospects for advancing engineering, social, and biological technologies; and the potential for selected research efforts to impact the U.S. military in general and the U.S. Army in particular over different timescales. Initially the committee was divided into three working teams. Team I devoted its attention to assessing the impacts of past network science and technology and to extrapolating this record to project future impacts. Team II focused on defining the scope of network science. Its members identified the core elements of network science underpinning the diverse array of applications and technologies in the social, economic, engineering, and biological arenas. Team III concentrated on outreach to communities that currently practice network science and technology. It identified community members via literature studies, interviews, and e-mail inquiries. It constructed and circulated a Web-based questionnaire. From the responses, it extracted the recognized core content of network science, research activities in which community members are engaged, and their perception of the major research challenges. The three streams of activity carried out by the teams were brought together midway though the committee’s deliberations with the writing of a full-message draft. Consensus was reached on the findings pertinent to charges (1) and (2) in the statement of task. Then, in response to charges (3) and (4) the committee was reconstituted into three new teams, which developed scenarios of how network science could add value for the Army. The committee’s findings, conclusions, and recommendations were then refined and ratified at the final meeting. REPORT ORGANIZATION This report documents the study approach, findings, conclusions, and recommendations. It is organized in accord with the statement of task in Box 1-2 and the study approach described above. Where the committee conducted research and discovered factual information, the information is reported as a finding. Multiple findings combine as the basis for conclusions, some “overarching” and the rest “specific” conclusions pertinent to specific requests in the statement of task. The conclusions are contained in Chapter 8 along with the committee’s recommendations. The bulk of the committee’s results are reported as findings in Chapters 2 through 7. Some of the details that support these findings are presented in the appendixes; others may be found in the references cited in the text. Chapter 2 characterizes the pervasive impact of networks and network research in the 21st century. Chapter 3 describes their significance for the military in general and the Army in particular. Chapter 4 offers a provisional definition of “network science” and notes the promise afforded by developing a science of networks. Chapter 5 describes the potential scope and content of network science, as determined from an analysis of courses at academic institutions worldwide. The contents of these courses are indicated in Appendix C. Chapter 6 discusses the current status of network science and identifies associated research challenges. This material is based on an analysis, presented in Appendix D, of the results of a questionnaire sent to over 1,000 researchers working on various topics pertaining to networks. Chapter 7 presents findings concerning how the Army can create value from investments in network science. It is based on the investment scenarios presented in Appendix E. Finally, as noted above, Chapter 8 contains the committee’s conclusions and recommendations.
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Network Science REFERENCES Arquilla, J., and D. Ronfeldt. 2001. Networks and Netwars: The Future of Terror, Crime and Militancy. Santa Monica, Calif.: RAND. Bernstein, P.J. 1992. Capital Ideas: The Improbable Origins of Modern Wall Street. New York, N.Y.: Free Press. Business Week. 2005. The power of us. Pp. 74–82. Cebrowski, A., and J. Garstka. 1998. Network centric warfare. Proceedings of the United States Naval Institute 24: 28–35. Garstka, J., and D. Alberts. 2004. Network Centric Operations Conceptual Framework Version 2.0. Vienna, Va.: Evidence Based Research, Inc. Johnson, S. 2001. Emergence: The Connected Lives of Ants, Brains, Cities and Software. New York, N.Y.: Scribner Associates, Inc. Rheingold, H. 2002. Smart Mobs: The Next Social Revolution. Cambridge, Mass.: MA Basic Books. Ronfeldt, D. 2005. A long look ahead: NGOs, networks, and future social evolution. In Environmentalism and the Technologies of Tomorrow, R. Olson and D. Rejeski, eds. Washington, D.C.: Island Press. Watts, D.J. 2003. Six Degrees: The Science of a Connected Age. New York, N.Y.: W.W. Norton. Weiner, T. 2005. Drive to build high-tech army hits cost snags. New York Times, March 28, 2005.
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