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Proceedings of the HCI'94 Conference on People and Computers IX

Fullname:Proceedings of the Ninth Conference of the British Computer Society Human Computer Interaction Specialist Group
Note:People and Computers IX
Editors:Gilbert Cockton; Stephen W. Draper; George R. S. Weir
Location:Glasgow, Scotland
Dates:1994-Aug-23 to 1994-Aug-26
Publisher:Cambridge University Press
Standard No:ISBN 0-521-48557-6; hcibib: BCSHCI94
  1. Invited Papers
  2. Methodology of Interactive Systems Development
  3. Crafting Interaction: Styles, Metaphors, Modalities and Agents
  4. Modelling Humans, Computers and their Interaction
  5. Notations and Tools for Design
  6. Computer-Supported Cooperative Work

Invited Papers

The Future of Graphic User Interfaces: Personal Role Managers BIBAK 3-8
  Ben Shneiderman; Catherine Plaisant
Personal computer users typically manage hundreds of directories and thousands of files with hierarchically structured file managers, plus archaic cluttered-desktop window managers, and iconic representations of applications. These users must deal with the annoying overhead of window housekeeping and the greater burden of mapping their organizational roles onto the unnecessarily rigid hierarchy. An alternate approach is presented, Personal Role Manager (PRM), to structure the screen layout and the interface tools to better match the multiple roles that individuals have in an organization. Each role has a vision statement, schedule, hierarchy of tasks, set of people, and collection of documents.
Keywords: Personal role manager, Desktop metaphor, Graphic user interface, Coordination, Computer-supported cooperative work (CSCW)
Beyond the Workstation: Mediaspaces and Augmented Reality BIBAK 9-18
  Michel Beaudouin-Lafon
The embodiment of computers in desktop workstations has had a tremendous impact on the field of HCI. Now that mice and graphics displays are everywhere, the workstation defines the frontier between the computer world and the real world. We spend a lot of time and energy transferring information between those two worlds. This could be reduced by better integrating the real world with the computer world. This article describes two approaches to this integration: Mediaspaces, which allow people to communicate through an audio, video and computer environment, and Augmented Reality, which adds computational power to real world objects. The argument is made that the success of these approaches lies in their ability to build on fundamental human skills, namely the ability to communicate with other people and the ability to interact with objects in the real world.
Keywords: Mediaspace, Augmented reality, Multimedia, Video, Virtual reality, Paper interface, Gesture input, Metaphor paradigm

Methodology of Interactive Systems Development

Transferring HCI Modelling and Design Techniques to Practitioners: A Framework and Empirical Work BIBAK 21-36
  Simon Buckingham Shum; Nick Hammond
The human-computer interaction (HCI) community is generating a large number of analytic approaches such as models of user cognition and user-centred design representations. However, their successful uptake by practitioners depends on how easily they can be understood, and how usable and useful they are. We present a framework which identifies four different 'gulfs' between HCI modelling and design techniques and their intended users. These gulfs are potential opportunities to support designers if techniques can be encapsulated in appropriate forms. Use of the gulfs framework is illustrated in relation to three very different strands of work:
  • i. representing HCI design spaces and design rationale;
  • ii. modelling user cognition; and
  • iii. modelling interactive system behaviour. We summarise what is currently known about these gulfs, report empirical investigations showing how these gulfs can be 'bridged', and describe plans for further investigations. We conclude that it is desirable for practitioners' requirements to shape analytic approaches much earlier in their development than has been the case to date. The work reported in this paper illustrates some of the techniques which can be recruited to this end.
    Keywords: Theory-based design, Evaluation, Design rationale, Cognitive modelling, Formal specification
  • The Use of Visual Indexing as an Interview Support Technique BIBAK 37-51
      David Fulton
    Systems analysts have a number of techniques at their disposal when capturing or generating the requirements for a system. One of the most commonly used is the interview. Interviewing users and other members of the client organisation is often fraught with difficulty: social and communicational barriers may prove difficult to overcome, especially if the level of contact between developers and users is kept to a minimum. Poor interview technique, ignorance of incorrect implicit/unspoken assumptions and the misinterpretation of interview data can lead to incorrect requirements or incomplete specifications. This paper describes a technique for developing a collaborative visual representation of information gathered during the interview process which enhances understanding between participants and enriches the information gathered. The method combines the manipulation of graphical objects and informal discussions which are collected via cassette or video recording. Graphical representation objects -- representing the groups, procedures, tools and products that exist in the interviewee's experience -- provide a standard, structured means of visual expression. Recording of walkthroughs and discussions of the results keeps note-making to a minimum and helps to reduce the social distance between the participants. A description of the four main stages of the technique is presented, along with supporting material outlining reasons why the technique was developed and describing how it has been used on organisational case studies. The paper concludes with an assessment of the effectiveness of the technique and suggests how it could be tailored to support requirements capture for system design.
    Keywords: Problems in communication, Interviews, Visual thinking, Visual description, System design
    A Domain Analysis of Air Traffic Management Work can be Used to Rationalise Interface Design Issues BIBAK 53-65
      John Dowell; Ian Salter; Solaleh Zekrullahi
    The demand for a more effective Air Traffic Management system, and the central role of the controller in that system, has focused attention on the design of the controller's interface. This paper presents an analysis of the task domain of Air Traffic Management. It demonstrates with a simulated system how the domain analysis can be used to model the controller's performance in the traffic management task. The use of this model in rationalising interface design issues is then illustrated. The analysis supports the general case for explicitly capturing the task domain in interface design.
    Keywords: Task domain, Domain analysis, Air traffic management, Task quality, Interface design
    Manuals as Structured Programs BIBAK 67-79
      Mark Addison; Harold Thimbleby
    A user manual may provide instructions that, if the user follows them, achieve any of certain objectives as determined by the manual designers. A manual may therefore be viewed rather like a computer program, as pre-planned instructions. Accordingly, software engineering and its methods may be applied mutatis mutandis to the manual and its design process.
       We consider structured programming methods, and show that some difficulties with user interfaces may be attributed to manuals being 'unstructured'. Since there are many programming metrics, and very many styles of manuals for user interfaces, this paper is concerned with justifying the approach and showing how insightful it is.
    Keywords: Manuals, Hypertext, Multimedia, Finite state machines, Flowgraphs
    Improving Education through Computer-Based Alternative Assessment Methods BIBAK 81-90
      Jody Paul
    Assessment contributes to the educational process of students but only a small fraction of the full potential is typically realized. The primary impediment to realizing greater benefit is the infeasibility of implementing more effective alternatives in the resource-limited settings typical of modern educational environments. We are developing a system architecture that exploits hypermedia technology to overcome serious limitations of traditional assessment methods. The architecture addresses the design of cost-effective confidence-measuring and performance-testing assessment vehicles using hypermedia-based student-system interaction. In this paper we describe the conceptual foundation, its embodiment in prototypes, and preliminary results from classroom tests.
    Keywords: Educational Assessment, Hypermedia, Computer-assisted education
    Visual Programming in a Visual Domain: A Case Study of Cognitive Dimensions BIBAK 91-108
      Francesmary Modugno; T. R. G. Green; Brad A. Myers
    We present a new visual programming language and environment that serves as a form of feedback and representation in a Programming by Demonstration system. The language differs from existing visual languages because it explicitly represents data objects and implicitly represents operations by changes in data objects. The system was designed to provide non-programmers with programming support for common, repetitive tasks and incorporates some principles of cognition to assist these users in learning to use it. With this in mind, we analyzed the language and its editor along cognitive dimensions. The assessment provided insight into both strengths and weaknesses of the system, prompting a number of design changes. This demonstrates how useful such an analysis can be.
    Keywords: Cognitive dimensions, End-user programming, Programming by demonstration, Visual language, Visual shell, Pursuit
    Evaluating Evaluation Methods BIBAK 109-121
      A. Dutt; H. Johnson; P. Johnson
    In HCI the aim of evaluation is to gather information about the usability or potential usability of a system. This paper is principally concerned with evaluating the effectiveness of two discount user inspection evaluation methods in identifying usability problems in a commercial recruitment database system with complex interface and system functionality. The two specific inspection methods investigated are heuristic evaluation and cognitive walkthrough. Several comparisons are made between the number, nature and severity of usability problems highlighted, the time needed to employ the methods and the ability to generate requirements for re-design. The results indicate that the methods are best considered as complementary and both should be employed in, but perhaps at different stages of, the design process.
    Keywords: Evaluation, Usability inspection methods

    Crafting Interaction: Styles, Metaphors, Modalities and Agents

    A Comparison of Placement Strategies for Effective Visual Design BIBAK 125-143
      Jean Vanderdonckt; Missiri Ouedraogo; Banta Ygueitengar
    The development of graphical user interfaces for interactive applications is subject to a series of well-known problems which could be relevant of the domain of visual design. This typically includes the problem of placing aesthetically interaction objects (IO) according to principles applied in placement strategies. This paper first reviews the problem of IO placement and shows the rationale for the most significant placement strategies found today. It then tries to compare six such strategies along several dimensions and mathematical relationships with respect to three points of view: the designer's point of view, the human factors expert's point of view, and the user's point of view.
    Keywords: Arrangement, Dimensioning, Interaction object, Localization, Interaction object placement, Placement strategy, Visual design
    Evaluation of Alternative Operations for Browsing Hypertext BIBAK 145-162
      Maria da Graca Campos Pimentel
    The aim of the Previewing Information Operation (PIO) approach is to tackle some overhead factors imposed on the user-hypertext interaction. The purpose is to diminish cognitive overhead and disorientation problems by reducing some of their causes.
       This paper describes an experiment carried out to evaluate the usability of the operations based on the PIO approach. Results from between-groups studies show that subjects' evaluation of the ease of use of the system and feeling of general orientation were affected by the presence of PIO operations. A further study has revealed that the PIO operations were predicted by standard navigational operations.
    Keywords: Hypertext, Link selection, Previewing information, Evaluation
    On the Problem of Selecting Interaction Objects BIBAK 163-178
      Francois Bodart; Jean Vanderdonckt
    This paper surveys and critically examines the literature dealing with selection rules for interaction objects. This analysis permits the definition of:
  • i. the premises of selection rules in terms of attributes from an
        object-oriented data model;
  • ii. the conclusions in terms of abstract interaction objects from an
        object-oriented model; and
  • iii. a generalized definition of selection rules. Finally, it endeavours to provide a more complete set of selection rules for elementary, composite, and specific data.
    Keywords: Interaction tools and techniques, Interaction object, Design process, Model-based interface tools, Selection, Object-oriented programming, User interface management systems
  • Minimising Conceptual Baggage: Making Choices about Metaphor BIBAK 179-194
      Ben Anderson; Michael Smyth; Roger P. Knott; Marius Bergan; Julie Bergan; James L. Alty
    This paper introduces a pragmatic model of the use of metaphor in human-centred system design. It identifies a number of issues implied by the model and describes an experimental investigation of a subset of these issues. Three interfaces were developed in order to compare the effect on perceived and actual user understanding of different metaphors for a common underlying functionality. The investigation demonstrates that it is not only important to ensure a close coupling between metaphor and system, but that it is equally important to consider the likelihood that users will make incorrect inferences from the metaphor. The paper concludes that the pragmatic model provides a technique that can be of use to interface designers in addressing this problem.
    Keywords: Metaphor, Telecommunications, Multimedia
    Keeping an Eye on your Interface: The Potential for Eye-Based Control of Graphical User Interfaces (GUI's) BIBAK 195-209
      Howell O. Istance; Peter A. Howarth
    This paper examines the issues surrounding the use of an eyetracker, providing eye-movement data, as a general purpose input device for graphical user interfaces. Interacting with computers via eye-movements is not in itself new, however previous work in the area has been directed towards interaction with purpose-built software which can take into account device limitations such as accuracy. This work investigates how one can interact with unmodified graphical interface software which normally requires mouse and/or keyboard input. The results of three experiments are discussed which have compared performance between the eyetracker and the mouse, and between different ways of emulating mouse button presses using the eyetracker data. The experiments as a whole consider a range of tasks from simple button presses to the more complex and demanding operations of selecting text, and they indicate the feasibility of using the eyes to control computers.
    Keywords: Physically-challenged, Eye-control, Input device
    A Linguistic Approach to Sign Language Synthesis BIBAK 211-222
      Alan Conway; Tony Veale
    This paper describes a linguistically motivated approach to synthesising animated sign language. Our approach emphasises the importance of the internal, phonological structure of signs. Representing this level of structure results in greatly reduced lexicon size and more realistic signed output, a claim which is justified by reference to sign linguistics and by examples of sign language structure. We outline a representation scheme for phonological structure and a synthesis system which uses it to address these concerns.
    Keywords: Deaf sign language, Phonological structure, Human animation
    Generalisation and the Adaptive Interface BIBAK 223-238
      Jonathan Hassell; Michael Harrison
    Automated macro systems which apply re-use to a user's input are a possible solution to the problems of customising an interactive system to the needs of the user. More useful than simple re-use would be a system that makes use of general patterns in users' behaviour and encapsulates this knowledge for application in similar, yet unfamiliar, circumstances. This process we term generalisation. This paper outlines some issues involved in controlling generalisation and the presentation and interaction with these macros, and specifies applicable heuristics. Finally the architecture for building an adaptive agent to perform the whole process is presented, with an example prototype operating on UNIX command-line interaction.
    Keywords: Adaptive interfaces, Interface customisation, Interface transformation, Command reuse, Agent modelling, Initiative
    Agent-Based Interaction BIBAK 239-245
      Russell Beale; Andrew Wood
    Agents are becoming widespread in a variety of computer systems and domains, but often appear to have little in common with each other. In this paper we look at different agent systems and identify what a generic agent should be composed of. We also identify the characteristics of a task that make it worthy of an agent-based approach. We then discuss the implications for the interaction of using agents, that is, the notion of a balanced interface, and briefly look at how an agent-based approach assists in two very different application domains.
    Keywords: Agents, Intelligent interfaces, Groupwork, Computer-supported cooperative work (CSCW)

    Modelling Humans, Computers and their Interaction

    Multi-Perspective Modelling of Interface Design Issues: Undo in a Collaborative Editor BIBAK 249-260
      Richard M. Young; Gregory D. Abowd
    Successful interface design respects constraints stemming from a number of diverse domains analysed by different disciplines. Modelling techniques exist within the individual disciplines, but there is a need for ways to weave together different techniques to provide an integrated analysis of interface design issues from multiple perspectives. We illustrate the relations and interplay between six different modelling techniques -- two for system modelling, two for user modelling, one for interaction modelling, and one for design modelling -- applied to a shared design scenario concerning the provision of an Undo facility for a collaborative editor. The resulting multi-perspective analysis provides a depth of understanding and a breadth of scope beyond what can be achieved by any one technique alone.
    Keywords: User modelling, System modelling, Design rationale, Interaction analysis, Multi-disciplinary analysis, Scenario analysis, Undo, Multi-user, Editing
    Qualitative Models of User Interfaces BIBAK 261-272
      Mark Treglown
    Analogy is an important factor in learning unfamiliar computer systems and problem solving when using those systems. Designers of computer systems can aid novice users by exploiting analogies and explicitly representing a model world with which the users are familiar as part of the user interface. Objects in the model world, and some operations that may be performed on them, are often analogous to those in the real world. We consider the qualitative reasoning approach to modelling people's knowledge of the real world and attempt to build qualitative models of objects and operations in the model world of a user interface. These models reveal features of existing systems that cannot be explained in terms of users' knowledge of the real world and suggest limits to direct engagement with on-screen objects.
    Keywords: Analogy, Qualitative reasoning, Direct engagement
    Modelling Interaction using Template Abstractions BIBAK 273-284
      Chris Roast
    The use of formal system models in interface development is often criticised for failing to recognise the 'human' nature of interaction. This paper describes an abstract system model of interaction, termed the template model, which is designed to address this criticism (Roast, 1993). The template model relies upon the identification of template abstractions which are system components that have particular user significance. By employing template abstractions system properties can be linked closely to user requirements. Using this framework we describe two categories of system constraint that express general usability requirements output correctness and structural consistency.
       The appropriateness of the perspective offered by the template model and the requirements expressed using it are illustrated in the analysis of an electronic mail system.
    Keywords: Formal methods, System modelling, Interaction models, Email
    The Formal Analysis of Human-Computer Interaction During Accident Investigations BIBAK 285-297
      Chris Johnson
    Many safety-critical applications rely upon complex interaction between computer systems and their users. When accidents occur, regulatory bodies are called upon to investigate the causes of user 'error' and system 'failure'. Reports are drawn up so that the designers and operators of future systems will not repeat previous 'mistakes'. These documents present the work of specialists who are drawn from many different technical disciplines: human factors; forensic investigation; engineering reconstruction; computer simulation; etc. The findings of these different experts are often separated into different sections. This creates a number of problems. Important evidence can be hidden within numerous appendices. The interaction between systems and users can be obscured by tortuous cross referencing schemes. There are occasional temporal ambiguities and inconsistencies between the different analyses. This paper presents ways in which formal methods can be exploited to address these problems. Mathematical notations provide means of representing and reasoning about the circumstances that lead to accidents in human machine systems. Executable logics can also be used to simulate event sequences. These simulations might be shown to other analysts. They can be used to encourage agreement on the course of events prior to more detailed investigations.
    Keywords: Safety-critical systems, Temporal logics, Formal methods, Simulation

    Notations and Tools for Design

    XUAN: Enhancing UAN to Capture Temporal Relationships among Actions BIBAK 301-312
      Phil Gray; David England; Steve McGowan
    Time is one of the most vital properties of an interface from a user's point of view, and the TAU project aims to explore how temporal properties of user interfaces affect their usability. This paper describes the XUAN notation of the specification of temporal behaviour. This notation also provides the basis for a software tool allowing not only specification but also rapid instantiation and modification of (small) user interfaces with defined temporal behaviour. This in turn will support rapid experimentation on users that varies temporal aspects on interfaces. In this paper we describe the features we have added to the UAN in creating XUAN in order to express temporal properties of tasks.
    Keywords: Task description language, Response time, Specification
    Structured Notations to Support Human Factors Specification of Interactive Systems BIBAK 313-326
      Kee Yong Lim; John Long
    The paper illustrates the use of structured notations to support the specification of various aspects of a system design; such as organisational hierarchies, conceptual level tasks, domain semantics, human-computer interactions, etc. In contrast with formal or algebraic notations, graphical structured notations are communicated to users more easily. Thus, user feedback elicitation and design validation would be supported better throughout system development. It is expected that the structured notations illustrated in the paper, could be used more widely for two reasons; namely they support more specific task specifications, and have now been incorporated into a structured human factors method. In addition, off-the-shelf computer-based support for the notation is emerging, e.g. PDF.
    Keywords: Graphical structured notations, Human factors specification, Structured human factors method
    Discount Dialogue Modelling with Action Simulator BIBAK 327-338
      Andrew F. Monk; Martin B. Curry
    A description of the high level structure of a user interface is an important part of any system specification. Currently the most common way of thinking about and recording this part of the design is through story boards and verbal descriptions, these may be imprecise and are difficult to evaluate. Action Simulator allows a designer to build simple models of the high level behaviour of the user interface. The models are easy to read and can be executed to give a dynamic view of the design. This makes it possible to 'run through' the actions needed to complete the users' work. A procedure for characterising the users' work that is suitable for this purpose is also sketched out in the paper. Action Simulator consists of an Excel spreadsheet and associated macros and is publicly available.
    Keywords: Dialogue model, Task model, Work objective, Decomposition, Scenario, System behaviour, Specification, Spreadsheet
    Executable Task Analysis: Integration Issues BIBAK 339-352
      Conn V. Copas; Ernest A. Edmonds
    Executable task models are considered to hold promise for increasing the impact of task analysis upon software engineering. However, this approach generates a number of integration issues when user interface management systems (UIMS) are employed at run-time. A number of models of integration are proposed and critiqued, employing a task scenario which involves the customisation of a geographic information system. Some current UIMS are shown to militate against this integration on account of the dominance which is accorded to the application. Some current task representations are shown to pose integration problems on account of both their procedural nature, and neglect of the application. One organising theme of the paper is that of executable task models being considered as particular cases of knowledge-based systems.
    Keywords: Task analysis, User interface management systems, Knowledge-based systems, Geographic information systems, Rapid prototyping, Knowledge representation, Formal methods, User modelling
    Beyond Data Models for Automated User Interface Generation BIBAK 353-366
      Angel R. Puerta; Henrik Eriksson; John H. Gennari; Mark A. Musen
    Researchers in the area of automated design of user interfaces have shown that the layout of an interface can, in many cases, be generated from the application's data model using an intelligent program that applies design rules. The specification of interface behavior, however, has not been automated in the same manner, and is mostly a programmatic task. Mecano is a model-based user-interface development environment that extends the notion of automating interface design from data models. Mecano uses a domain model -- a high-level knowledge representation that augments significantly the expressiveness of a data model -- to generate automatically both the static layout and the dynamic behavior of an interface. Mecano has been applied successfully to completely generate the layout and the dynamic behavior of relatively large and complex, domain-specific, form- and graph-based interfaces for medical applications and several other domains.
    Keywords: Model-based interface development, Automated interface design, Interface models, Domain models, Data models

    Computer-Supported Cooperative Work

    Designing a User Interface for Folding Editors to Support Collaborative Work BIBAK 369-381
      Richard J. King; Ying K. Leung
    Software engineering requires the production of hierarchically organised text-based documents, such as specifications, source codes, and manuals. Folding editors are effective tools designed to support such activities involving documents of any complexity. In a collaborative work environment, especially in a large software development team, folding editors offer many advantages over the conventional editing system. Surprisingly, the use of folding editors has often been overlooked. This could partly be attributed to the generally inadequate design of their interface and partly to the lack of effective facilities available to support collaborative work.
       This paper identifies some of the typical difficulties associated with sharing files in a software engineering teamwork environment and discusses the advantages of folding editors to overcome these problems. It then describes the rationale of a design of a user interface for folding editors to support collaborative work.
    Keywords: Folding editors, Computer-supported cooperative work (CSCW), Groupware, User interface design, Software engineering, CASE tools, Collaborative writing
    Collaborative Use of X-Windows Applications in Observational Astronomy BIBAK 383-396
      Darryn Lavery; Alistair Kilgour; Pete Sykes
    This paper describes a case study in the design and prototyping of a system to support shared use of application programs in an X Windows environment. The primary aim was to satisfy the requirements for remote observation at Royal Observatory Edinburgh. The starting point for the software development was an existing tool 'Shared-X', developed to support window-sharing in X Windows. The paper describes the analysis of requirements for safe and efficient shared control in the remote observing situation. Previous work in groupware and application sharing is reviewed, and the architecture for the target system is related to existing taxonomies. The modifications that were necessary to the Shared X tool are described, in particular an improved and extended mechanism for floor control, which was found to be an important factor in the acceptability and usability of the system in the target domain. However limitations in the underlying X Windows architecture and having no access to the shared X source code prevented full implementation of the specification for shared telepointers. In conclusion the work highlights the importance of key issues in collaborative system design, including the importance of flexible and transparent mechanisms for floor control, the effective representation of status and control information in the user interface, the need for appropriate support mechanisms in the underlying window system (e.g. for multiple telepointers), and the increased complexity of evaluation with collaborative as opposed to single-user systems.
    Keywords: Computer-supported cooperative work (CSCW), Groupware, Realtime conferencing, Shared window servers, Shared X
    Que Sera Sera -- The Problem of the Future Perfect in Open and Cooperative Systems BIBAK 397-408
      Alan Dix
    When the pace of interaction with a task is too slow, the user's execution/evaluation loop is broken. Feedback normally says what has happened. However, when the task is slow, nothing has happened yet -- the interest shifts to what will have happened. This poses two problems for the user. Firstly, recalling the appropriate context when a response eventually arrives. Secondly, maintaining the expectation that the response will come and when, so that appropriate action can be taken if it fails to materialise. The design question is how to support these activities, of which the latter has received little emphasis to date.
    Keywords: Cooperative work, Computer-supported cooperative work (CSCW), Delayed feedback, Status/event, Response time
    Viewpoints, Actionpoints and Spatial Frames for Collaborative User Interfaces BIBAK 409-423
      Steve Benford; Lennart E. Fahlen
    Synchronisation is a key issue for collaborative user interfaces. An examination of current approaches, in particular the concept WYSIWIS and the use of Video as a communication medium, highlights a number of issues in this area including lack of a common spatial frame of reference, lack of appropriate embodiment of users and inflexible and rigid communication channels between users. The paper then proposes a new framework for designing collaborative user interfaces which addresses these issues. This framework is based on the notion of a common spatial frame within which embodied users are free to move autonomously, being casually aware of each other's activities. Embodiment is considered in terms of both individual viewpoints and actionpoints (e.g. telepointers) within the display space. We propose that, in many cases, synchronisation of the spatial frame is necessary but synchronisation of viewpoints and actionpoints may actually inhibit collaboration. We finish by describing some prototype systems which provide one (of possibly many) examples of how our framework might be employed; in this case to create shared cooperative virtual environments.
    Keywords: Synchronisation, Video, WYSIWIS, Virtual reality, Multi-user interface, Computer-supported cooperative work (CSCW)