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COVEN (Collaborative Virtual Environments) is a European project that seeks to develop a comprehensive approach to the issues in the development of collaborative virtual environment (CVE) technology. COVEN brings together twelve academic and industrial partners with a wide range of expertise in CSCW, networked VR, computer graphics, human factors, HCI, and telecommunications infrastructures. After two years of work, we are presenting the main features of our approach and results, our driving applications, the main components of our technical investigations, and our experimental activities. With different citizen and professional application scenarios as driving forces, COVEN is exploring the requirements and supporting techniques for collaborative interaction in scalable CVEs. Technical results are being integrated in an enriched networked VR platform based on the dVS and DIVE systems. Taking advantage of a dedicated Europe-wide ISDN and ATM network infrastructure, a large component of the project is a trial and experimentation activity that should allow a comprehensive understanding of the network requirements of these systems as well as their usability issues and human factors aspects.

A vital component of any application or environment is security, and yet this is often one of the lower priorities, losing out to performance and functionality issues, if it is considered at all. This paper considers a spatial approach to enabling, understanding and managing access control that is generally applicable across a range of collaborative environments and applications. Access control is governed according to the space within which subjects and objects reside, and the ability to traverse space to get close to an object. We present a framework that enables the SPACE access model [4], previously presented as an access model solely for collaborative virtual environments, to be applied across a number of collaborative systems. This framework is exemplified through mappings of the model to 3D and 2D collaborative environments, namely Spline [ 11, TeamRooms [ 191 and Orbit [ 161. One particularly interesting feature of the model is the way in which it handles group access by considering how group credentials are determined. These credentials are presented to the model in the usual manner. We conclude by presenting some limitations of our approach, and workarounds.

Collaborative virtual environments (CVEs) are a promising technology enabling remote participants to share a common place through three-dimensional graphical scenes. Within the COVEN project (Normand, 1999), we have run prolonged series of Internet trials that have allowed us to gather valuable data to formulate usability guidelines and networking requirements. However, running such trials in a real setting and making sure that the application and networking infrastructures will be stable enough is still a challenge. In this paper, we describe some of our experiences, together with the technical choices that have permitted many hours of successful Internet trials. We also make a thorough analysis of different correlated logging data. This analysis allows us to propose and con rm a model of a CVE application's network behavior, together with a number of interesting results that disprove some common assumptions. Furthermore, we use the model and the logging data to highlight the bene ts of IP multicasting and for predicting traf c behaviors and bandwidth use on top of different logical network topologies.