Abstract. This article describes an ontological model of norms. The basic assumption is that a substantial part of a legal system is grounded on the concept of agency. Since a legal system aims at regulating a society, then its goal can be achieved only by affecting the behavior of the members of the society. We assume that a society is made up of agents (which can be individuals, institutions, software programs, etc.), that agents have beliefs, goals and preferences, and that they commit to intentions in order to choose a line of behavior. The role of norms, within a legal system, is to specify how and when the chosen behavior agrees with the basic principles of the legal system. In this article, we show how a model based on plans can be the basis for the ontological representation of norms, linking them to the upper level of a philosophically well-founded ontology (DOLCE); in this way, the model is set in a wider perspective, which opens the way to further developments. 1