While many writers and researchers have studied CAS, a concise nominal definition does not exist. The essential principles of CAS have been taken from each of these works and synthesized into a single description. The description is purposefully concise. The basic building blocks of the CAS are agents. Agents are semi-autonomous units that seek to maximize some measure of goodness, or fitness, by evolving over time.
Agents scan their environment and develop schema representing interpretive and action rules.
These schema are often evolved from smaller, more basic schema. Schema exist in multitudes and compete for survival. The fitness of the agent is a complex aggregate of many factors, both local and global. The general health or fitness of the agent determines what the probability of change will be. In general the probability of second order schema change is a nonlinear function of the fitness value.