A central aim of the COVEN project was to prototype large-scale applications of collaborative virtual environments (CVEs) that went beyond the existing state of the art. These applications were used in a series of real-scale networked trials that allowed us to gather many interesting human and technological results. To fulfill the technological and experimental goals of the project, we have modified an existing CVE platform: the DIVE (distributed interactive virtual environment) toolkit. In this paper, we present the different services and extensions that have been implemented within the platform during the four years of the project. Such a presentation will exemplify the different features that will have to be offered by nextgeneration CVE platforms. Implementation of the COVEN services has had implications at all levels of the platform: from a new networking layer through to mechanisms for high-level semantic modeling of applications.