A New Landmark of Study on System Complexity -On the Development and Inspiration of the Complex Adaptive System Theory

CAS (short for "complex adaptive system") theory advanced by Holland broke through the limitation of previous study on the complex systems from a new visual angle. This paper introduces in detail the origin and development, traits, applications and the meaning on methodologies of the theory. The study of the system complexity is very important in the contemporary scientific study. CAS theory has provided new thinking methods to know, understand, control and manage the complex systems for the researchers. Holland defines the complex adaptive system as such systems that consist of large number of individuals that interact by sending and receiving signals and adapt or learn as they interact. These individuals are called as "adaptive agents" enjoying very large initiative and positivity and the internal mechanism of these agents are defined as the classifier systems. The basic frame of CAS theory includes four characteristics- aggregation, nonlinearity, flow, diversity and three mechanisms- tagging, internal model, building blocks of the adaptive agent, and the stimulus-response model of the agents and Echo Model of the macrosystem. Holland describes them by means of metaphorical method and suggests the computer-based modeling and simulating method should be adopted mainly to study the complex adaptive system.