Centrality is not an intrinsic attribute, but a relative one
Centrality is the property of that which is central : that is, that is linked to the center . The concept has different uses according to the context.
Centrality of a node
In the field of social network analysis and graph theory , centrality is a measure that is associated with the relevance of a node (also understood as an actor or simply a vertex ). It can be estimated according to where the node's paths begin and end in the network or according to what other paths traverse the node that is taken as a reference point.
There are several centrality indices or measures that serve to determine and quantitatively compare the relative importance that a node has in the structure that defines the network. Generally, these measures are normalized, so that they are enclosed in the range from 0 to 1, so that different cases and networks can be compared, since the result we obtain can be interpreted as a percentage, instead of an absolute value.
It is important to note that this is a structural and not an intrinsic attribute of the nodes: it is a value that is linked to their relationships with others within the network. Take the case of a road network. By analyzing the centrality of a node , you can discover which is the most important road in the group, but this does not mean that outside the network, if we isolated it, the node would have the same importance.
In certain cases, such as asymmetric or directed relationships , that is, networks that are represented in the form of directed graphs , the term centrality is not used, but status or prestige . The terms deference, rank and popularity , among others, may also appear.
History
The first to talk about this concept was the North American psychosociologist Alex Bavelas , in 1948. In fact, the sociological origin of centrality can be seen in the different theories that revolve around it. Between then and the beginning of the following decade, the growing importance of centrality can be observed when discussing topics such as social networks and sociograms.
This occurred at the same time that formal studies of cliques (or cliques , a group of vertices in which every pair is adjacent, that is, connected by an edge) appeared in sociomatrices. Bavelas's study was the starting point for an important development in social network analysis ; A clear example is found in the appearance of graph theory , fundamental in this context.
In politics
In the field of politics , the idea of centrality refers to those issues and problems that dominate the agenda . One can also talk about the centrality of politics with reference to its importance in solving social problems and improving the quality of life of the population .
Urbanism defines centrality as the coexistence and crossing of polarities
For urban planning
In the field of urban planning , centrality implies the coexistence and crossing of polarities (frameworks composed of a main activity and other complementary ones). It is understood that the center of a locality, in this framework, is the physical space where consumption and employment are generated simultaneously with the corresponding control by private and public entities subordinate to the legislation.
The center is characterized by presenting a particular architecture and a specific infrastructure that allow it to differentiate itself from other areas and give it prestige. The centrality in the organization of the city and in the distribution of resources makes the periphery aspire to resemble the center.