A major challenge in the research of multiagent systems (MAS) is the design and implementation of open MAS in which norms can be effectively applied to their agents and easily managed. These tasks are arduous because norms are usually written for general purposes, hindering a more precise regulation. The motivation for this research came forth from the need to resolve this challenge, providing an approach applicable in open systems. In such systems, heterogeneity and autonomy rule out any assumption concerning the way third-party entities are implemented and behaved. In this paper, a norm-based approach for the modeling of open MAS, named DynaCROM, is presented. The paper also summarizes the result of a study that focuses on solutions for the modeling of MAS and that motivated the development of our DynaCROM approach.