While globalization and informatization progress, information networks typified by the Internet gets attention. Therefore, the term network is often conscious of strong linkage with information. However, a network is diverse and ambiguous concept that includes not only relation to information but also relation to people, organizations, systems, and the like. Focusing on "network" studies, many researchers are studying from both aspects of social science and natural science. The former are research fields such as interorganizational relations, network organization, communication network, and so on. The latter are research fields such as information networks, information communication networks, graph theory and probability theory, and so on.