THE LESSON LEARNT FROM Freeman, L. 1978. Centrality in social networks: Conceptual clarification

First introduced by Bavelas in 1948, the idea of centrality in human community has been recognized. The centrality was related to group efficiency in problem solving, perception of leadership, and the personal satisfaction of participants. And, before arguing centrality, the graph-theory is necessary, where the words: "adjacent, degree of point, path, cycle, connected, distance, geodesics" have their unique meaning. 

In the terms of point centrality, "a point that falls on the communication paths between other points exhibits a potential for control of their communication." And, a central position is one that is not dependent upon others as intermediaries or relayers of messages. Short distances mean fewer message transmissions, shorter times, and lower costs. Especially, concern with communication activity will suggest a degree-based measure, interest in control of communication requires a measure-based upon betweenness; and concern with either independence or efficiency leads to the choice of a measure based upon closeness.