Olof Hagsand

DIVE—A platform for multi-user virtual environments

Abstract The Distributed Interactive Virtual Environment (DIVE) is an experimental software platform for the development of multi-user virtual reality applications. DIVE uses active replication and reliable multicast protocols to distribute data between participants. The distribution model enables a large number of users and applications to participate and interact in the same virtual environment. The DIVE platform offers a wide range of interaction support and user-related abstractions to ease the task of application and user interface construction.

Interactive multiuser VEs in the DIVE system

Multiuser virtual environments (VEs) raise challenging research questions concerning how users interact with objects, applications, and other users, and how distributed VEs behave when the number of users increases. The Distributed Interactive Virtual Environment (DIVE) is a software platform for multiuser VEs that has served as a toolkit for many distributed VE applications. It emphasizes networking and human-computer interaction and supports autonomous behavior-driven objects, collision detection, and audio and 3D navigation.

DIVE A multi-user virtual reality system

The Distributed Interactive Virtual Environment (DIVE) is a heterogeneous distributed virtual reality system based on UNIX and Internet networking protocols. Each participating process has a copy of a replicated database and changes are propagated to the other processes with reliable multicast protocols. DIVE provides a dynamic virtual environment where applications and users can enter and leave the environment on demand. Several user-related abstractions have been introduced to ease the task of application and user interface construction.<<ETX>>

Generation of visual language-oriented design environments

We review some results in the area of using meta techniques to generate language-oriented programming environments. We focus on environments for visual languages having a two-dimensional syntax based on attribute grammars and graphical constraints. We introduce edit-semantic attributes, a new class of attributes which control the user interaction and graphic presentation. We present LOGGIE, a prototype tool implementing some of the meta techniques discussed. The tool generates interactive language-oriented graphical editors. A number of applications have been generated and are presented, e.g. graphical environments for CCS, G-LOTOS and SDL.

Issues in the design of a scalable shared virtual environment for the Internet

Building a distributed virtual environment that scales to many participants in low bandwidth, high latency networks is a technical challenge. The key issues are maintaining acceptable performance in the face of high latency links, and maintaining consistency of shared world data between multiple participants. The paper describes the overall architecture that enables one to build such a wide area, shared virtual environment targeted to the Internet. The architecture relies on spatial partitioning of the shared scene to reduce communication, replication to hide latency, and group communications to maintain replica consistency. The paper discusses the generic architecture, the key issues that must be solved and then presents two implementations of that architecture and gives performance results from one of those implementations.

Using spatial techniques to decrease message passing in a distributed VE system

In an attempt to reduce the communication costs in a shared distributed virtual environment (VE) system with a large number of participants, we have explored the use of SP* tial interaction techniques. In particular, we have experimented with the notion of an area of interest (AOI) which is dynamically established based on the spatial proximity of participants in the shared space. The work presented here describes an effort to integrate an enhanced aura-based spatial interaction model within the DIVE distributed Virtual Environment system and use this to reduce the overall communication load in the system. By associating light-weight communication groups to AOIS (area of interest), we show how messages are distributed to smaller peer groups, so that overall message pawing is de creaaed. A multi-user application scenario is implemented aa a case study. Real experiments and measurements with the current DIVE system using the scenario were made to validate the interaction model and its implementation. This work waa performed aa a joint research effort between Sony CSL and SICS as part of the Wide Area Virtual Environment (WAVE) project.

The definition of a graphical G-LOTOS editor using the meta-tool LOGGIE

Abstract We present a prototype implementation of a graphical editor for a subset of G-LOTOS. The graphical G-LOTOS syntax is being standardized within ISO for the LOTOS specification language. First, we provide a formal definition of the G-LOTOS subset. Then, the specification of the editor is derived from this formal definition. Finally, such a specification is used for the automatic generation of the editor by means of the LOGGIE meta-tool.

ATM as a Link in an ST-2 Internet

ATM promises to be a broadband network that provides quality of service guarantees for real time multimedia applications. ST-2 is an experimental connection-oriented protocol that provides guaranteed support for streams across an internet of hosts and routers. We describe an implementation of an ATM network as one link in an ST-2 internet. We explain how the ST-2 flowspec is mapped into an ATM hopspec during connection establishment. We then show that, after connection establishment, ST-2 header prediction can be performed on an ATM network to minimize protocol overhead. Finally, we argue that the current ATM adaption layers do not provide the right service for ST-2 or other variable length packet protocols designed to carry continuous media.

OS6-a distributed operating system for the next generation of computer networks

Flexibility to adapt to radically different network environments will be key to the success of new distributed operating systems. An operating system must be able to support the distribution of objects on high bandwidth fiber-optic as well low-bandwidth wireless networks. In this position paper, we provide a sketch of OS6, a new operating system being designed to provide low latency run-time services in distributed environments made up of both high and low bandwidth networks. Efficient distribution of objects is maintained by special operating system agents that pre-fetch and cache data facilities as well as guard object consistency. Network-level multicast filtering supports the replication and consistency tasks performed by these agents. Support for mobility is provided by persistent virtual memory which guarantees consistent object state across reboots of the machine. Real-time quality of service guarantees for distributed multimedia applications are supported by a meta-scheduler that maps real-time operating system threads onto network flows with guaranteed resources.<<ETX>>