TABLE 2-1 Representative Networks

Biological Networksa

Physical Networks

Social Networks

Type of Network

Global Impact

Type of Network

Global Impact

Type of Network

Global Impact

Disease transmitting networks (HIV, influenza, TB, malaria, cholera)

Spread of disease, epidemics

Distribution grids (electric power, water supply, business supply chains)

Efficient distribution of goods or commodities

Affiliation/ acquaintance networks (terrorist, community, business, religious, clubs)

Efficient collaboration and activity coordination

Ecological networks (food webs, river basins, rain forest)

Survival of selected species; global weather and topography

Telecommunications infrastructure (cellular, PSTN, cable TV, Internet)

Instantaneous worldwide information distribution

Broadcast networks (radio, TV networks like NBC, CBS, CNN)

Dissemination of identical information to large groups

Metabolic networks

Sustenance of life for a given generation of living entities

DOD global information grid (sensors, communications, and weapons)

Network-centric warfare and network-enabled operations

Information exchange networks (U.S. mail, local and long-distance telephone service)

Cheap, convenient long distance pair-wise communications

Community networks (insect societies, animal herds, bird flocks, schools of fish)

Survival of selected species

Transportation networks (airports, highways, railways, shipping)

Rapid movement of goods from supplier to market; modern travel

Group forming networks (eBay, corporate intranets)

Easy, convenient formation of groups of like-minded people who have never met

Gene expression networks

Transmission and evolution of life between generations

Electronic financial transaction networks (banking, credit cards, ATMs)

Electronic cashless transactions

Supply chains and business networks

Coordination of multiple players to achieve common goals, global cost reduction





Social services networks (Social Security, family services, Medicare, Medicaid)

Efficient delivery of government services to large, distributed constituencies

NOTE: PSTN, public switched telephone network; DOD, Department of Defense.

aIncludes biochemical and other networks that are natural rather than manmade.

management, and customer relationship management depend. From overseas manufacturer to Wal-Mart, products are ordered electronically, produced on demand, shipped around the globe by shipping networks, and delivered to local stores by rail and truck networks. Heralded by some pundits as the century of biology and nanotechnology, the 21st century is in fact an era of networks and is called by others “The Age of Information and Telecommunications” (Perez, 2002).

Finding 2-3. Social and biological networks bear important similarities to engineered networks.

One might infer from Table 2-1 that biological and social networks are similar to engineered networks. Indeed, much recent literature has been devoted to documenting just how this is the case (Barabási, 2002; Bower and Bolouri, 2001; Dorogovtsev and Mendes, 2003; Newman, 2003; Watts, 2003). The important point for this study is that many methods and models are applicable to networks of all kinds: biological, physical, and social. (These commonalities are explored in Chapter 5 and Appendix C.)

Finding 2-4. Advances in computer-based technologies and telecommunications are enabling social networks that facilitate group affiliations, including terrorist networks.

An important property of networks is that they may be built on top of each other. For example, a social network may be formed based on an information network built on a communications network that utilizes a physical network of transmission equipment. This property enables experimentation in the social network realm using commercial com-

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