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VI.5 Sept.-Oct. 1999
Page: 7
Digital Citation

What’s happening


Authors:
Jennifer Bruer

ACM Quest for Windows CE™

Applications Winners

ACM held the first ACM Quest for Windows CE™ Applications Supported by Casio®, Everex®, Hewlett Packard®, & Microsoft®. The Winners were notified in May, 1999. The following is a list of the winners and their categories.

Marshall Ramsey – Individual Winner Education and Science
The entry can be demonstrated at the following location: http://ai.bpa.arizona.edu/~mramsey/kingkanji.html

Phil Nachreiner and Robert Wlodarczyk – Team Winners Calculators/Engineering/Finance
The entry can be demonstrated at the following location: http://www.nachreiner.com/matrix/

Daniel Bui – Judges Award Overall Most Original
The entry can be demonstrated at the following location: http://www.cise.ufl.edu/~ddbui/medpad

Todd Ostermeier and Dave Draeger – Team Winners IR Control/Communication
The entry is currently not available to be demonstrated.

Kirk Bulis – Individual Winner Calculators/Engineering/Finance
The entry can be demonstrated at the following location: http://www.cs.ucla.edu/~kbulis/simulator/index.html

Robert Miller, Carl Evankovich, Ben Bostwick – Team Winners Personal Productivity
The entry can be demonstrated at the following location: http://www.cs.cmu.edu/~pebbles/.

Jolon Faichney – Individual Winner IR Control/Communication
The entry is currently not available to be demonstrated.

Dmitriy Beryoza – Individual Winner Personal Productivity
The entry can be demonstrated at the following location: http://www.cs.fiu.edu/~beryozad/wince

Vincent Deschenes – Individual Winner Games/Sports
The entry can be demonstrated at the following location: http://www.gel.ulaval.ca/~desche02/TrackMan/projet.htm

A Trio of Notebook Computer Keypads Are Launched By Genovation

Genovation has begun shipping three new numeric keypads for portable computers. The Micropad™ keypads are primarily designed to ease the entry of numeric data into portable computers by accountants and other financial professionals.

Although these keypads share a number of common features such as very low power consumption, 18–key switches with tactile feedback and a standard dark gray case, they each feature a different interface to the PC. The Micropad 631 features a ISB interface, the Micropad 632 has a pass-through PS/2 interface (dual connector), and the Micropad 633 has a serial interface.

These new keypads take advantage of the latest technologies in circuit and switch designs, and offer high reliability at low costs. The Micropad 631 and 632 will price below $35, and the Micropad 633 below $45. For more information see http://www.genovation.com.

Call for Participation

3rd Annual Applied Ergonomics Conference to be held March 14–16, 2000 at the Wilshire Grand Hotel in Los Angeles, CA, USA.

The Applied Ergonomics Conference is devoted to sharing successful ergonomics applications. Over 100 presentations in a four-track format cover applications in areas such as manufacturing/service, construction/office, design/engineering products, rehabilitation/health management, ergonomics programs, and potpourri (cost justification, auditing, etc.).

One of the conference special events is the presentation of the "ERGO Cup." The competition recognizes team efforts to combine ergonomic principles and innovation to jobs in the workplace. ERGO Cup teams present a demonstration that features job changes that improved the fit between the work and the person, the financial success of the solution and the involvement of people in the workplace.

For conference registration information visit the conference web site at http://www.iienet.org/conted/ergoconf.htm.

Electronic Wallet Helps People Who Are Visually Impaired

The Electronic Wallet, with a built-in beeping feature that alerts wallet owners whenever a credit card is removed, is now being used by people who are partially sighted and blind to keep better track of their credit cards, identification and money.

The Electronic Wallet operates by using a small microchip and a standard, replaceable watch battery with a three-year warranty. Sensors in the credit card pockets detect when a card is removed and trigger the beeping sound if the card is not returned. The wallet beeps every 20 seconds until the card is replaced. The beeping mechanism shuts off automatically after five minutes. The security feature is hidden in the interior of the wallet and does not significantly add to the weight or size of the wallet.

The Electronic Wallet comes in numerous different styles, for both men and women. A complete product line is available at http://www.accessorycity.com

"Human-Centered Computing, Online Communities and Virtual Environments"

Report on the first joint European Commission/National Science Foundation Advanced Research Workshop, June 1 – 4, 1999, Chateau de Bonas, France

bullet.gif Introduction and Background

This joint Workshop was set up under the auspices of the Joint European Commission/National Science Foundation Strategy Group that had its first meeting in Budapest, 3-4 September 1998. The meeting derived from a joint collaboration agreement between the EC and NSF in August 1998, signed by Dr. George Metakides (Director, Information Technologies, EC) and Prof. Juris Hartmanis (Director, CISE, NSF). The collaboration aims to facilitate the joint development of knowledge and applications in key emerging science and technology areas of mutual interest. Successful cooperation holds the promise of more cost-effective investment of research funds in the USA and the European Union.

National initiatives in the USA and many European countries are recognizing the benefits to scientific research in supporting larger groupings, often with interdisciplinary teams of researchers. It is possible to achieve results with national and translation groupings that it is not possible to achieve on the same time scale with an institutional one. This model has also been used for a number of years by the European Commission to facilitate research development in European countries, and accomplish faster technology transfer to European industry by company participation in projects. These initiatives have recently been extended to include non-European partners on a self-funded basis. Collaborative links have also been established with Japan. It is clear that with the increasing globalization of research and development there is a need for research laboratories and companies to develop products that are viable in world markets. Thus what is being proposed by the EC and NSF is a logical extension of existing paradigms for securing significant progress in key research areas.

It was felt desirable to arrange a series of research Workshops to enable early identification of key research challenges and opportunities in information technology. It was intended that each Workshop should bring together eminent scientists and technologists in the USA and Europe in the area being addressed, and that the themes would emanate from the research community.

At the meeting of the Joint EC/NSF Strategy Group on 3-4 September, a number of possible themes were identified. These included "human-centered computing and virtual environments", "large-scale scientific databases", and "intelligent implants". Scientists on this Strategy Group included: Prof. Andy van Dam (Brown University, USA), Prof. Paul Messina (California Institute of Technology, USA), Prof. Rae Earnshaw (University of Bradford, UK), Prof. Giorgio Baccarani (University of Bologna, Italy), Prof. Rolf Eckmiller (University of Bonn, German) and Prof. Gilles Kahn (Inria, France).

It was agreed that the first joint research Workshop should concentrate on the themes of human-centered computing and virtual environments. Human-centered computing is perceived as an area of strategic importance because of the move towards greater decentralization and decomposition in the location and provision of computation. The area of virtual environments is one where increased collaboration should facilitate more rapid progress in solving some of the more intractable problems in building effective applications. It is intended that further Workshops should follow this one, either on separate topics or on specific issues arising out of this first Workshop.

bullet.gif Objectives of the Workshop

The objective of the Workshop was to concentrate on the research frontiers of human computer interaction and virtual environments. Of particular relevance are the desires that interaction be more centered around human needs and capabilities, and that the human environment be considered in virtual environments and in other contextual information processing activities. The overall goal is to make users more effective in their information or communication tasks by reducing learning times, speeding up performance, lowering error rates, facilitating retention and increasing subjective satisfaction. We believe that improved designs can dramatically increase effectiveness for users who range from novices to experts and who are in diverse cultures with varying educational backgrounds. Their lives could be made more satisfying, their work safer, their learning easier and their health better. Research areas to be addressed included:

  • high level content descriptions and their access, such as metadata and MPEG7
  • reducing cognitive load and providing more scope for creativity
  • cross-disciplinary interaction and how to make it work
  • handling interaction in specific social contexts and with cultural differences
  • dealing with universality and the problems of the differently-abled
  • interaction styles and their implications
  • consistency of cognition models across information appliances
  • paradigms for emerging new kinds of interaction; beyond WIMP interfaces: multimodal and perceptual user interfaces
  • challenges for virtual environment technology and interfaces
  • usability issues and measuring the effectiveness of symbiosis
  • design and evaluation of online communities for intranet and internet
  • scaling online communities to support millions of people
  • universal access, social and ethical issues

Each participant at the Workshop produced a position paper on a selected topic, which was used to feed the discussions at the Workshop. The participants then formed Working Groups to discuss in detail the research issues in particular domains. These areas were defined by the functional research issues that came into the Workshop through the position papers, not by any external body.

The results and recommendations from the Workshop are intended to inform the process of collaboration between the EC and the NSF on the development of mechanisms to support international level collaborative research and to identify optimal areas in which cooperation could take place. These results are also being circulated to the community in journals and newsletters for discussion and comment. This present document is formal the Report to the European Commission and the National Science Foundation on the Workshop. A book is also to be produced containing the material considered at the Workshop.

The Workshop Program

International researchers and key actors in the fields of virtual environments and human-centered computing were invited to prepare position papers in areas covered by these areas. Figure 1 shows the attendees at the Workshop.

The position papers submitted to the Workshop determined the first cut at possible research priorities, and they were grouped into the following principal areas:

  • Virtual environments
  • Augmented reality and mobile computing
  • Devices for display and interaction
  • Future interfaces
  • Applications and tools
  • Online communities
  • Foundations for interaction
  • Collaboration between industry, academia and government

Following the initial review of the areas, they were combined into the following:

  • Virtual environments, augmented reality and mobile computing
  • Applications and tools
  • Devices and future interfaces
  • Online communities
  • Collaboration between industry, academia and government

Working Groups in these five areas further considered the detailed research issues. Their reports follow this summary.

bullet.gif The Principal Results from the Workshop

Virtual Environments and Human-Centered Computing

Although virtual environments and human-centered computing are rather different areas, it proved to be very useful to have researchers joining together to consider the issues on the lines of continuum between the two areas. Virtual environments face challenges, especially in the areas of display technology, interaction methodologies, update rates and collaboration between users in different geographic locations. A mobile augmented reality environment is challenged by portability issues, devices, interfaces and communications. It is difficult to make computing human-centered with standardized technology such as keyboards and mice, impedance mismatches, and the current shift towards ubiquity. As a result of this ubiquity, the computation will become incorporated in mobile devices or embedded in the infrastructure or the environment, rather than in a particular desktop device with which the user can interact. There are challenges in steering technological innovation towards meeting human needs, in ensuring that the results of empirical research are useful to designers and in orienting the system developer to think more in terms of the human user. Output devices can range between the two extremes of light emitting polymers for coating wall paper (for large-scale, wall-sized displays) and small-scale retinal displays, where the image is focused directly on the retina.

bullet.gif Diversity of Technology and Users

The current diversity of the field, such as in displays, is both a challenge and an opportunity. Current developments in technology and content generation, and the rapid rise of new uses and applications, require diverse kinds of interdisciplinary expertise in order to exploit the technology effectively. There is a diversity of technology (hardware, software, and networking), a diversity of users (especially in areas where technology has not yet made significant inroads) and an increasing gap between what users know and what they need to know to use current systems effectively. All this bears testimony to tools and systems being technology-driven rather than user-driven. Much more attention needs to be given to end-to-end design and integrating the needs of the user from the very beginning. Critical parameters in the design and evaluation process need to be much more firmly identified, quantified and rigorously upheld. Research is needed in this area.


Much more attention needs to be given to end-to-end design and integrating the needs of the user from the very beginning.

 


bullet.gif Research Integration

The wide range of expertise available at the Workshop enabled us to recognize the challenge of diversity and seek to address it. It was agreed that the breadth of the field is not being taken into account by current research. The experts in converging areas are not working together, and research programs are not getting the right kind of interdisciplinary expertise, or support, to give added-value integration. Indeed, the need for a greater degree of integration and greater attention to scalability pervaded many of the research issues highlighted at the Workshop.

bullet.gif Multiple Disciplines

One important area of future work is the behavior of individuals and communities in their relationship to each other and to the world. There is a long history of educational, psychological, social psychological and sociological studies, but methodological innovations are needed to capture and understand the complex nature of individual and group behaviors that occur while using technology. Analytic and descriptive studies can provide useful insights, but there is a strong need for more prescriptive outcomes that can guide designers of new technologies. Guidelines are available for basic user interface design, and these need to be extended to accommodate new technologies. In addition, validated metrics, user surveys, task taxonomies, ethnographic methods of observation, participatory design methods, usability testing strategies, expert review techniques and software development methodologies would all help produce more orderly development processes for new technologies. Social impact statements prepared in advance of implementations could facilitate broad discussions of critical technologies and thereby minimize the number and severity of unanticipated side effects.

Understanding community relationships becomes even more critical when it is a community of users interacting in a shared world or information space, such as on the World Wide Web. The interface needs to be appropriate to the task to be performed, the social behavior of the user (or groups of users), and the maintenance of relationships. Research programs should be developed in this area.

Strong encouragement should be given for universities to support multidisciplinary activities and to reform traditional computer science departments so that they include a human-centered approach throughout their research and educational programs. A specific suggestion for moving the center of gravity in this direction would be to fund graduate fellowships in human-centered systems.

bullet.gif Pure and Applied Research

The resistance to a full recognition of the value of interdisciplinary research was felt to reside in both funding bodies and academia. Academia prefers promotion criteria that emphasize "pure" science, with elegant solutions being derived for somewhat arbitrary intellectual problems; funding bodies promote research areas recommended by scientific peer groups in the same tradition. This roadblock to interdisciplinary research must be overcome. Currently academia is losing many valuable people to industry simply because industry is paying them to do the kind of exciting and meaningful research they are unable to do in academia and get tenure. There is a lack of synchronization between academia, the changing nature of the world and the research needed to shed light on important current issues.

Much stronger promotion of evaluation and empirical testing of systems in the context of work is needed. This evaluation and testing should be both controlled and ethnographic, in the laboratory and in the field. Needs, requirements and behavior of the users, as well as the range of problems they need to solve, should be considered. Progress in VR, online communities, universal usability and other user-centered areas will be dramatically increased if the funders insist on some form of assessment.

bullet.gif Key Application Drivers

Problems to be solved can be key drivers in the domain. These represent in some sense "pull" requirements from the user that need to be considered alongside the more normal "push" technology from the vendors. The Working Group that considered the agenda for collaboration between industry, academia, and government, proposed the "Content" age as the key driver for 2010. Content is needed for human media technology, augmented reality, digital story telling, interactive broadcasting and multimedia workspaces. Indeed, the whole nature of the human-computer interface may move away from one operating on a model of sequential task definition and processing. The new human-computer interface could operate on a model of behavior, context, cultural background, information awareness and imagination, namely "story-telling" at the interface, thus drawing on its own values of context and history.

A working model and methodology is needed for the Content Age. The technology should be user-centered and mobile with new types of interaction technology and information display. Three key application domains have requirements for this technology:

  • Health and continuing medical education (both doctors and patients)
  • Environment
  • Cultural heritage

It is proposed that a follow-up Workshop should be organized on this theme with content experts, perceptualization experts and representatives of potential funding sources from governments and industry. The objective would be to stimulate and integrate government and academic research agendas in this area.


Much stronger promotion of evaluation and empirical testing of systems in the context of work is needed.

 


bullet.gif The Networked Community

Current developments in online communities present a major strategic opportunity for the information technology (IT) community. This is another key application driver. Although the nature of these new communities is not well understood, because of their rapid growth, they have the potential for changing the world, especially in the developing countries.

As the community moves towards the "million person interface" what will the needs and requirements of the community be, and how should they be supported? How can multi-cultural and multi-lingual requirements be handled and represented? These are complex and difficult challenges, and there is an opportunity to make a significant impact on the world stage.

Universality need not imply a loss of functionality for particular domains and applications, nor should it be seen necessarily as "lowest common denominator" IT. However, the global nature of the online communities phenomenon does present a major strategic opportunity for governments to collaborate on research in this area — thus benefiting from the pooling of expertise from different cultures backgrounds, and countries.

bullet.gif A Taxonomy of Human-Centered Systems

An initial taxonomy for human-centered computing in the context of virtual environments was produced. This provides a framework for an understanding of multi-channel input and output, the skills of the user, the particular technology selected for a task and the task to be performed (whether simple or complex). A foreground and background task model is proposed, and it highlights two key issues for the future:

  • How to get foreground and background to assist each other
  • How to increase the effective contribution of the background (i.e. to make the computer more aware of the user’s context, needs, and requirements at any point in time).

The following section reports the recommendations from each of the five Working Groups:

  • Virtual environments, augmented reality and mobile computing
  • Applications and tools
  • Devices and future interfaces
  • Online communities
  • Collaboration between industry, academia and government

Acknowledgments

We express our thanks and appreciation to the European Commission and the National Science Foundation for co-sponsoring the Workshop. We are also grateful to the following organizations for support and assistance: Brown University, University of Bradford, Fraunhofer IGD, INT, and the British Computer Society.

This report has been brought together by amalgamating the reports of the Working Groups at the Workshop, and we would like to fully acknowledge the contributions of all the participants.

Thanks are due to Nic Chilton (University of Bradford, UK) for his assistance in the preparation of this report for typesetting.

Author

Judith R. Brown (University of Iowa, USA), Andy van Dam (Brown University, USA), Rae Earnshaw (University of Bradford, UK), Jose Encarnacao (Fraunhofer IGD, Germany), Richard Guedj (INT, France), Jennifer Preece (University of Maryland Baltimore County, USA), Ben Shneiderman (University of Maryland College Park, USA), John Vince (Bournemouth University, UK)

Figures

F1Figure 1. Attendees at the first Joint EC/NSF Workshop
Front Row (left to right): Karine Iannelli (Secretariat), Ute Fahrholz (Secretariat), Emilie Monferran (Secretariat), Prof Richard Guedj (Co-Chair), Margaret Denison (Secretariat), Judy Brown, Prof Rae Earnshaw (Co-Chair), Mrs. Simone (host), Second Row (left to right): Lisa Manekofsky (Brown University, USA), Prof Bertram Herzog (Fraunhofer CRCG, USA), Junji Yamaguchi (Independent researcher, Japan), Dr. Larry Rosenblum (Naval Research Laboratory, USA), Prof Ben Shneiderman, Prof Jenny Preece, Dr. Wendy Kellogg (IBM T. J. Watson Research Center, USA), Dr. John Thomas (IBM Research Hawthorne, USA), Third row (left to right): Prof Tosiyasu Kunii (Hosei University, Japan), Prof Andy van Dam (Co-Chair), Debbie Van Dam, Jo Herzog, Dr. Matthew Turk (Microsoft Research, USA), Dr. Charles Koelbel (National Science Foundation, USA), Dr. Jürgen Schönhut (Fraunhofer IGD, Germany), Prof Mikael Jern (AVS and Linkoping University, Sweden), David Leevers (VERS, UK), Christoph Busch (Fraunhofer IGD, Germany), Prof Tom DeFanti (University of Illinois at Chicago, USA), Fourth Row (left to right): Hartmut Chodura (Fraunhofer IGD, Germany), Dr. Sudhir Mudur (National Centre for Software Technology, India), Dr. Thomas Kirste (Fraunhofer Institute, Germany), Dr. Deb Roy (MIT Media Laboratory, USA), Dr. Turner Whitted (Microsoft Research, USA), Back row (left to right): Prof Tom Furness (HIT Laboratory, University of Washington, USA), Prof Bill Buxton (Alias Wavefront/Silicon Graphics, University of Toronto, Canada), Prof John Vince, Also attending but not shown: Victor Abrash (SRI International, USA), Prof Daniel Andler (University of Paris X, France), Jehan Bing (SRI International, USA), Prof Ole Bernsen (Odense University, Denmark), Prof José Encarnação, Dr William Newman (Xerox Research Centre Europe, UK).

Sidebar: Summary of Recommendations

This section gives a list of the recommendations produced from the Working Groups.

GENERAL

Recommendation 1
More research consideration should be given to human needs and requirements, rather than technology functions per se.

Recommendation 2
Research is required to identify the critical parameters involved in the design and evaluation of technology to meet user needs.

Recommendation 3
Mechanisms and procedures for facilitating interdisciplinary research collaborations are needed.

Recommendation 4
A greater emphasis is needed on quantitative and predictive methods for analyzing user behavior and user requirements that can be used to inform the technology design process and its interface to the user.

Recommendation 5
Research programs should be developed on interfaces for tasks, social behavior of users, and the maintenance of relationships.

Recommendation 6
To provide practical and political support for multidisciplinary approaches, funding should be made available for graduate fellowships in human-centered systems.

Recommendation 7
Current roadblocks to interdisciplinary research must be overcome, especially those caused by the research grant proposal review process and faculty tenure considerations.

Recommendation 8
Funding agencies should insist on evaluation and testing of systems in the context of their intended domain of use.

Recommendation 9
Content should be a key driver for the next phase of developments, and this will open up new interface requirements.

Recommendation 10
A working model and methodology for content must be defined.

Recommendation 11
A Workshop should be arranged on the theme of a working model and methodology for the content age, with content experts, perceptualization experts, and representatives of potential funding sources from governments and industry.

Recommendation 12
An analysis should be performed to determine the need and requirements of the emerging online community.

Recommendation 13
We must take advantage of the strategic opportunity, available through the online community, to collaborate on Research and Development issues with potential global significance.

Recommendation 14
We should create a classification of user tasks into foreground and background activities, in the context of an overall framework for human-centered computing, in order to understand how to get technology to assist the user, both directly and indirectly.

VIRTUAL ENVIRONMENTS, AUGMENTED REALITY AND MOBILE TECHNOLOGY

Recommendation 15
In order to effectively utilize technology, the complexity of the user’s task(s) must be reduced.

Recommendation 16
Areas for future research in virtual environments, augmented reality and mobile technology are set in the report.

APPLICATIONS AND TOOLS

Recommendation 17
Research must be conducted into applications and tools that lead to better methodology.

Recommendation 18
Long-standing, independent organizations, such as Fraunhofer IGD in Darmstadt, Germany, should be invited to take responsibility for maintaining industry-standard platforms as they emerge. There may be a role to be played here by large organizations like the European Commission and National Science Foundation for the funding to cover this type of work.

Recommendation 19
The Virtual Environments community should build stronger relationships with the commodities and large-scale solutions sectors.

Recommendation 20
Increased emphasis on performance metrics is required.

Recommendation 21
We need to take steps to ensure continuity of infrastructure environments to protect the current investment in toolkits, component sets, and platforms.

Recommendation 22
We need to take into account the effects of commoditization of technology.

FOUNDATIONS OF FUTURE INTERFACES: DEVICES, HARDWARE AND SOFTWARE

Recommendation 23
Human-centered computing is increasing in complexity as the number of interacting users increases and their environments increasingly integrate real and virtual worlds via technology. This complexity needs to be taken into account in future research.

Recommendation 24
Recognizing these rapidly developing wider horizons to user interfaces is important in formulating steps to increasing their applicability and effectiveness. In addition, it has already been demonstrated that design strategies which facilitate use by the differently abled often increases the usability for all classes of users.

Recommendation 25
The report details research issues to do with displays, interaction methodologies, and interaction environments that are essential to address if we are to move forward with more intelligent devices, hardware, and software.

ONLINE AND NETWORKED COMMUNITIES

Recommendation 26
Research is needed by teams of social and technical scientists that will inform the design of all kinds of online communities. We need to understand cultural differences better and how to support diversity online.

Recommendation 27
We must understand and develop software that takes account of the ethical issues and universal access, a challenge for both technical and social scientists.

Recommendation 28
Theories from sociology, psychology, social psychology, linguistics, communications research and psychotherapy can help to inform research and development of online communities. Before this happens, research is needed to establish how such theories relate to communities supported by technologies.

Recommendation 29
Considerable research is needed to develop representations to reveal online behavior as it is occurring, as well as histories of behavior, stored communication and knowledge, nature of communication (e.g. which topics were discussed), the number of people participating and relationships between participants.

Recommendation 30
Research is needed to develop participatory, community-centered design and evaluation techniques. Approaches are needed to ensure that account is taken of different user and access needs.

Recommendation 31
Two crucial areas require substantial research in the near future in order to develop a powerful electronic market and eliminate lack of trust in online transaction. These are copyright protection and conflict between identification and privacy or anonymity.

Recommendation 32
Scalability is a research priority for online communities. With an increasing number of people from across the world joining all kinds of online communities, we must consider how we develop software and guide social processes to support very large communities.

Recommendation 33
We advocate research funding for supporting case study and ethnographic research that will enable us to better understand the needs of online health and education communities and networked communities in which online resources are integrated with physical resources to support community life.

BUSINESS, ACADEMIA, GOVERNMENT

Recommendation 34
We propose that an international R&D collaboration be developed to define a working model and methodology for content based on a common working platform UNIVIZ (a content, perceptualization, visualization, and networking platform.)

Recommendation 35
Three pilots of test Domains based on selected applications were written up in the report. Health and continuing medical education, the Environment and Cultural Heritage are increasingly important application areas world-wide. Funding should be provided for international, interdisciplinary collaborative projects in these application domains.

©1999 ACM  1072-5220/99/0900  $5.00

Permission to make digital or hard copies of all or part of this work for personal or classroom use is granted without fee provided that copies are not made or distributed for profit or commercial advantage and that copies bear this notice and the full citation on the first page. To copy otherwise, to republish, to post on servers or to redistribute to lists, requires prior specific permission and/or a fee.

The Digital Library is published by the Association for Computing Machinery. Copyright © 1999 ACM, Inc.

 

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