Concepts: Network
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A network is the connections that allow interactions and influences between parts of a complex system. It can also mean the system as a whole, when considering the effects of the connections within it.
There are many different types of networks, such as transportation networks whose links may be roads, communication networks whose links may be phone lines, nerve cell networks whose links may be synapses, and social networks whose links may be the various relationships between people in a community.
An important property of a network is its topology: which elements are directly connected to which others. The connections can also be characterized by properties such as their strength of influence or capacity (how much they can transfer).
Many networks are influence networks: the connected parts affect each other through the network. We can also distinguish between networks that transfer materials, such as transportation or chemical transmission networks, and those that transfer information, such as neural, computer, or social networks.
One may think about a network's connections as a system in their own right. For example, the transportation system is considered a system, even though it is a network connecting the parts of various social and economic systems. We can study properties of the connections, like traffic jams, rather than seeing them only as connections. We may also focus on how the parts behave as a result of their connections through the network, or how the system as a whole behaves due to both the parts and the connections.
A variety of commonly studied networks connect parts that are similar and have connections that are similar. Hence, the research focuses on a network's topology. Other networks, however, connect dissimilar parts in dissimilar ways, and it is important to take these diversities into account when studying network behavior.
As part of the study of complex systems, the understanding that we gain of how networks behave can be transferred between different kinds of systems, be they physical, biological, social or engineered. It is useful to consider which behaviors are common to different kinds of networks and which vary among them.
Related concepts: interdependence, hierarchy, control
See also:
Optimization of Robustness and Connectivity in Complex Networks
Benjamin Shargel, Hiroki Sayama, Irving R. Epstein and Yaneer Bar-Yam
Phys. Rev. Lett. 90, 068701 (2003)
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