Abstract. The interoperability between heterogeneous distributed virtual environments is one of the main problem Virtual Reality will have to face in the very close future. This article presents the main concepts we propose in NOV (which stands for Networked Open VirtuAl Environment). These concepts are presented as a set of paradigms based on the semantic of a virtual world and its virtual entities. Key-words : Networked Virtual Environments, Interoperability, Cooperative Work, Object Modeling.