Roles are being represented as a fundamental concept in most knowledge representation languages, mainly in the design of open software systems. Unknown entities playing their roles in such systems increase the opportunity to happen unpredictable and non-desired situations. Because of that, regulations over roles are necessary. In open multi-agent systems, it is required to have mechanisms to guide the behaviors of agents, especially when their behaviors affect other agents and the agents playing in it are unknown. Norms, characterized by their prescriptiveness, sociality and social pressure can police agents’ actions as a regulatory mechanism. This paper presents norms and ontologies’ definition for actions performed by agents. This approach defines that regulations have a semantic support provided by an ontology, specially designed and built for it. This ontology is a generic one and need to be extended for specific domains. An ontology for the urban traffic domain was extended and instantiated in an urban traffic simulator system, developed as a case study. The generic and extended ontologies are also presented in this paper.