This paper aims to analyze the decision process approaches implemented in a complex system, by focusing on the development of new public policies. Individual interviews were conducted with forty policy makers, as part of an experimentation about the intellectual property system. The results show that, in this system, the policy makers rely on decision process approaches that are consistent with the models of disjointed or logical incrementalism. Besides, these process approaches can vary on three aspects : the presence or not of external diplomatic activities, the use or not of decision cases considered similar, the nature of objectives pursued.