Society

Until the 20th-century, our society was structured in such a way that most social activities took place in what you could call the "physical real world. " After the last decade of the 20th-century, a "cyber network society " began to emerge thanks to the advancement of information and communication technologies (Fig. 1). While the physical real world is governed by physical and chemical laws such as gravity and human biological characteristics, activities in the cyber network society are designed based on “artificial ” standards, regulations, laws, and so on. To design 21st-century social infrastructures, therefore, it is crucial to study how we can integrate the physical real world and the cyber network society. One idea to realize this cyber-real integration is to link and merge dynamical flows in the physical real world and the cyber network society; the former is characterized by the flows of goods, people, and energy and the latter by the flow o