Define agent based simulation .

Agent-based simulation (ABS) is a computational modeling technique that simulates the actions and interactions of autonomous agents, both individual and collective, in an environment. Each agent has its own set of rules, behaviors, and characteristics, and they interact with each other and their environment. The overall system behavior emerges from these local interactions, rather than being dictated by a central controller. ABS is particularly useful for studying complex systems where emergent phenomena arise from the bottom up, such as in social sciences, ecology, and economics.