Using teleporting, awareness and multiple views to improve teamwork in collaborative virtual environments

Mobile Group Dynamics (MGDs) are a suite of techniques that help people work together in large-scale collaborative virtual environments (CVEs). The present paper describes the implementation and evaluation of three additional MGDs techniques (teleporting, awareness and multiple views) which, when combined, produced a 4 times increase in the amount that participants communicated in a CVE and also significantly increased the extent to which participants communicated over extended distances in the CVE. The MGDs were evaluated using an urban planning scenario using groups of either seven (teleporting + awareness) or eight (teleporting + awareness + multiple views) participants. The study has implications for CVE designers, because it provides quantitative and qualitative data about how teleporting, awareness and multiple views improve groupwork in CVEs. Categories and Subject Descriptors (according to ACM CCS): C.2.4 [Computer-Communication Networks]: Distributed Systems – Distributed applications; H.1.2 [Models and Principles]: User/Machine Systems – Human factors; Software psychology; H.5.1 [Information Interfaces and Presentation]: Multimedia Information Systems – Artificial, augmented and virtual realities; H.5.3 [Information Interfaces and Presentation]: Group and Organization Interfaces – Collaborative computing; Computer-supported cooperative work; Synchronous interaction; I.3.7[Computer Graphics]: Three Dimensional Graphics and Realism – Virtual Realit

Modules program structures and the structuring of operating systems

In this paper some views are presented on the way in which complex systems, such as Operating Systems and the programs to be interfaced with them can be constructed, and how such systems may become heavily library oriented. Although such systems have a dynamic nature, all interfacing within and among modules can be checked statically. It will be shown that the concepts presented are equally valid for single user systems, multi-programming systems and even distributed systems. The ideas have been spurred by the implementation of a modular version of Pascal and a supporting Operating System, currently nearing completion at Twente University of Technology, The Netherlands

Web-based support for managing large collections of software artefacts

There has been a long history of CASE tool development, with an underlying software repository at the heart of most systems. Usually such tools, even the more recently web-based systems, are focused on supporting individual projects within an enterprise or across a number of distributed sites. Little support for maintaining large heterogeneous collections of software artefacts across a number of projects has been developed. Within the GENESIS project, this has been a key consideration in the development of the Open Source Component Artefact Repository (OSCAR). Its most recent extensions are explicitly addressing the provision of cross project global views of large software collections as well as historical views of individual artefacts within a collection. The long-term benefits of such support can only be realised if OSCAR is widely adopted and various steps to facilitate this are described

How robust are distributed systems

A distributed system is made up of large numbers of components operating asynchronously from one another and hence with imcomplete and inaccurate views of one another's state. Load fluctuations are common as new tasks arrive and active tasks terminate. Jointly, these aspects make it nearly impossible to arrive at detailed predictions for a system's behavior. It is important to the successful use of distributed systems in situations in which humans cannot provide the sorts of predictable realtime responsiveness of a computer, that the system be robust. The technology of today can too easily be affected by worn programs or by seemingly trivial mechanisms that, for example, can trigger stock market disasters. Inventors of a technology have an obligation to overcome flaws that can exact a human cost. A set of principles for guiding solutions to distributed computing problems is presented

Using XML views to improve data-independence of distributed applications that share data

The development and maintenance of distributed software applications that support and make efficient use of heterogeneous networked systems is very challenging. One aspect of the complexity is that these distributed applications often need to access shared data, and different applications sharing the data may have different needs and may access different parts of the data. Maintenance and modification are especially difficult when the underlying structure of the data is changed for new requirements. The eXtensible Markup Language, or XML, has emerged as the universal standard for exchanging and externalizing data. It is also widely used for information modeling in an environment consisting of heterogeneous information sources. CORBA is a distributed object technology allowing applications on heterogeneous platforms to communicate through commonly defined services providing a scalable infrastructure for today\u27s distributed systems. To improve data independence, we propose an approach based on XML standards and the notion of views to develop and modify distributed applications which access shared data. In our approach, we model the shared data using XML, and generate different XML views of the data for different applications according to the DTDs of the XML views and the application logic. When the underlying data structure changes, new views are generated systematically. We adopt CORBA as the distributed architecture in our approach. Our thesis is that: views to support data-independence of distributed computing applications can be generated systematically from application logic, CORBA IDL and XML DTD.Dept. of Computer Science. Paper copy at Leddy Library: Theses & Major Papers - Basement, West Bldg. / Call Number: Thesis2002 .L86. Source: Masters Abstracts International, Volume: 41-04, page: 1113. Adviser: Richard Frost. Thesis (M.Sc.)--University of Windsor (Canada), 2002

Telepresence and Space Station Freedom workstation operations

The Space Station Freedom workstation system is a distributed network of computer based workstations that provides the man-machine interfaces for controlling space station systems. This includes control of external manipulator, robotic and free flyer devices by crewmembers in the space station's pressurized shirt-sleeve environment. These remotely controlled devices help minimize the requirement for costly crew extravehicular activity (EVA) time for such tasks as station assembly and payload support. Direct window views may be used for controlling some of the systems, but many activities will be remote or require levels of detail not possible by direct observation. Since controlling remote devices becomes more difficult when direct views are inadequate or unavailable, many performance enhancing techniques have been considered for representing information about remote activities to the operator. Described here are the telepresence techniques under consideration to support operations and training. This includes video enhancements (e.g., graphic and text overlays and stereo viewing), machine vision systems, remote activity animation, and force reflection representation

In-Network View Synthesis for Interactive Multiview Video Systems

To enable Interactive multiview video systems with a minimum view-switching delay, multiple camera views are sent to the users, which are used as reference images to synthesize additional virtual views via depth-image-based rendering. In practice, bandwidth constraints may however restrict the number of reference views sent to clients per time unit, which may in turn limit the quality of the synthesized viewpoints. We argue that the reference view selection should ideally be performed close to the users, and we study the problem of in-network reference view synthesis such that the navigation quality is maximized at the clients. We consider a distributed cloud network architecture where data stored in a main cloud is delivered to end users with the help of cloudlets, i.e., resource-rich proxies close to the users. In order to satisfy last-hop bandwidth constraints from the cloudlet to the users, a cloudlet re-samples viewpoints of the 3D scene into a discrete set of views (combination of received camera views and virtual views synthesized) to be used as reference for the synthesis of additional virtual views at the client. This in-network synthesis leads to better viewpoint sampling given a bandwidth constraint compared to simple selection of camera views, but it may however carry a distortion penalty in the cloudlet-synthesized reference views. We therefore cast a new reference view selection problem where the best subset of views is defined as the one minimizing the distortion over a view navigation window defined by the user under some transmission bandwidth constraints. We show that the view selection problem is NP-hard, and propose an effective polynomial time algorithm using dynamic programming to solve the optimization problem. Simulation results finally confirm the performance gain offered by virtual view synthesis in the network

Sensor networks and distributed CSP: communication, computation and complexity

We introduce SensorDCSP, a naturally distributed benchmark based on a real-world application that arises in the context of networked distributed systems. In order to study the performance of Distributed CSP (DisCSP) algorithms in a truly distributed setting, we use a discrete-event network simulator, which allows us to model the impact of different network traffic conditions on the performance of the algorithms. We consider two complete DisCSP algorithms: asynchronous backtracking (ABT) and asynchronous weak commitment search (AWC), and perform performance comparison for these algorithms on both satisfiable and unsatisfiable instances of SensorDCSP. We found that random delays (due to network traffic or in some cases actively introduced by the agents) combined with a dynamic decentralized restart strategy can improve the performance of DisCSP algorithms. In addition, we introduce GSensorDCSP, a plain-embedded version of SensorDCSP that is closely related to various real-life dynamic tracking systems. We perform both analytical and empirical study of this benchmark domain. In particular, this benchmark allows us to study the attractiveness of solution repairing for solving a sequence of DisCSPs that represent the dynamic tracking of a set of moving objects.This work was supported in part by AFOSR (F49620-01-1-0076, Intelligent Information Systems Institute and MURI F49620-01-1-0361), CICYT (TIC2001-1577-C03-03 and TIC2003-00950), DARPA (F30602-00-2- 0530), an NSF CAREER award (IIS-9734128), and an Alfred P. Sloan Research Fellowship. The views and conclusions contained herein are those of the authors and should not be interpreted as necessarily representing the official policies or endorsements, either expressed or implied, of the US Government