Vol. 24 · No. 1

Collaboration and teamwork is important in many areas of our lives. People come together to share and discuss ideas, split and distribute work or help and support each other. The sharing of information and artefacts is a central part of collaboration. This often involves the manipulation of shared objects, both sequentially as well as concurrently. For coordinating an efficient collaboration, communication between the team members is necessary. This can happen verbally in form of speech or text and non-verbally through gesturing, pointing, gaze or facial expressions and the referencing and manipulation of shared objects. Collaborative Virtual Environments (CVE) allow remote users to come together and interact with each other and virtual objects within a computer simulated environment. Immersive display interfaces, such as a walk-in display (e.g. CAVE), that place a human physically into the synthetic environment, lend themselves well to support a natural manipulation of objects as well a set of natural non-verbal human communication, as they can both capture and display human movement. Communication of tracking data, however, can saturate the network and result in delay or loss of messages vital to the manipulation of shared objects. This paper investigates the reality of shared object manipulation between remote users collaborating through linked walk-in displays and extends our research in cite27. Various forms of shared interaction are examined through a set of structured sub tasks within a representative construction task. We report on extensive user-trials between three walk-in displays in the UK and Austria linked over the Internet using a CVE, and demonstrate such effects on a naive implementation of a benchmark application, the Gazebo building task. We then present and evaluate application-level workarounds and conclude by suggesting solutions that may be implemented within next-generation CVE infrastructures.

This article describes the architecture and the network communication of a large-scale, networked virtual environment, which is designed to specifically support closely-coupled collaboration in highly interactive scenarios. Its main goals are the maintenance of low latency during user interaction and fast multicasting of messages in order to fulfill consistency requirements. This is achieved by sophisticated message distribution techniques, peer-to-peer connections between interacting clients and a global hierarchical communication topology. Scalability is realised through partitioning the virtual world.

Building collaborative applications is still a challenging task. A collaborative application can be viewed as a class of distributed shared memory system. A distinctive property of these systems is their memory consistency model. In this paper, we argue that there is a relationship between different collaboration styles, on the one hand, and different memory consistency models, on the other. In particular, we propose a practical collaboration style, exemplified by a collaborative electronic organizer, that can be supported by the GWO memory consistency model, a rather relaxed model stricter only than local consistency. The advantage of the proposed style is that it reduces the amount of information that must be exchanged among the processors. Because there have been no propositions of the specific rules—i.e., the protocol—that the processors in a system must follow to implement the GWO model, we also propose a protocol that exactly matches the properties of the model.

Synchronous collaborative systems allow geographically distributed participants to form a virtual work environment enabling cooperation between peers and enriching the human interaction. The technology facilitating this interaction has been studied for several years and various solutions can be found at present. In this paper, we discuss our experiences with one such widely adopted technology, namely the Access Grid. We describe our experiences with using this technology, identify key problem areas and propose our solution to tackle these issues appropriately. Moreover, we propose the integration of Access Grid with an Application Sharing tool, developed by the authors. Our approach allows these integrated tools to utilise the enhanced features provided by our underlying dynamic transport layer.

This paper presents the design, architecture and main implementation features of the flood prediction application of the Task 1.2 of the EU IST CROSSGRID footnoteThis work is supported by EU 5FP CROSSGRID IST-2001-32243 RTD project and the Slovak Scientific Grant Agency within Research Project No. 2/3132/23. project. The paper begins with the description of the virtual organization of hydrometeorological experts, users, data providers and customers supported by the application. Then the architecture of the application is described, followed by used simulation models and modules of the collaborative environment. The paper ends with vision of future development of the application.