A Flock Is Not a Bird Agents and Beyond :

a flock of birds sweeps the sky. One moment they are circling, another they dart to the left or drop to the ground. Each move is so beautiful that it appears choreo-graphed. Furthermore, the movements of the flock seem smoother than those of any one bird in the flock. Yet, the flock has no high-level controller or even a lead bird. The phenomenon is a result of what is often called " self-organization. " 1 Each bird follows a simple set of rules that it uses to react to birds nearby. In Craig Reynolds' simulation, 2 each bird behaved according to three simple rules: 1. Maintain a minimum distance from other objects, including other birds. 2. Try to match velocities with other birds. 3. Try to move toward the perceived center of the mass of birds in its neighborhood. Orderly flocks emerge from simple rules such as these. No one bird has a sense of an overall flock. The " bird in front " is merely a position of a given bird. It just happens to be there— and it will be replaced by others in a matter of minutes. " The flock is organized without an organizer, coordinated without a coordinator. " 1 Flocks of birds are not the only things that work like this. Beehives, ant colonies, freeway traffic, national and global economies, societies, and immune systems are all examples of patterns that are determined by local component interaction instead of centralized authority. Agents Another name for local component is agent. A basic dictionary definition of agent is " one who acts. " Under such a broad definition, agents can have a host of properties. One way to think about these properties is as follows 3 : • Autonomous. Exercises control over its own behavior and state. • Communicative. Socially able, communicates with other agents, such as humans, machines, and software agents. • Mobile. Able to transport itself from one environment or platform to another. • Reactive. Sensing and acting; responds in a timely fashion to changes in the environment. • Goal-oriented. Proactive, purposeful; does not simply act in response to the environment. • Temporally continuous. A continuously running process. • Flexible. Actions are not scripted. • Character. Believable " personality " and emotional state. • Able to learn and evolve. Learning; changes its behavior based on its previous experience. Most people who work with agents find this …