Abstract. In this paper we propose an emergence-driven software process for agent-based simulation that clarifies the traceability of micro and macro observations to micro and macro specifications in agent-based models. We use the concept of hyperstructures [1] to illustrate how micro and macro specifications interact in agent-based models, and show that the reductionism/non-reductionism debate is important to understand the reliability of agent-based simulations. In particular, we show that the effort expended in the verification of agent-based simulations increases exponentially with the number of micro and macro specifications, and that the reliability assessment of non-anticipated results in simulation is in practice not possible. According to these results we claim to be impossible in practice to verify that an agent-based conceptual model has been implemented properly as a computational model, since we do not usually know what we want the output to be a priori. We thus advocate that the classic process of verification, validation and exploration of non-anticipated results is not reliable in agent-based simulation, and call into question the applicability of traditional software engineering methods to agentbased simulation. 1