ABSTRACT
Complex systems represent one of the current main research directions in systems science, while complex adaptive systems (CASs) stand for a class of very representative complex systems. The theory of CASs is proposed by Holland (1996) based on his years of study on complex systems. The basic idea of this theory is that the complexity of CASs originates from the adaptation of individual elements or agents of the systems; it is the interactions between these individual agents and the environment and between these agents themselves that these agents evolve themselves and reshape the environment. The most important characteristic of CASs is their adaptation. That is, the systems’ individual agents can directly communicate with the environment and with themselves, and through such communications, these agents “learn” and “accumulate experience” so that they constantly evolve and improve. Based on the learned lessons, these agents alter their internal structures and modify their patterns of behavior. The agents at the very bottom level, through mutual interactions and communications, can produce new structures, phenomena, and more complex behaviors for the higher level and/or the whole level of the system. The interactions and communications of the agents at the very bottom level could create additional levels, dissolve an existing level, or produce multiplicity in the functionality or appearance of the system. They could also lead to the formation of new aggregates, larger agents, etc.
