Recent years have seen a shift in perception of the nature of HCI and interactive systems. As interface work has increasingly become a focus of attention for the social sciences, we have expanded our appreciation of the importance of issues such as work practice, adaptation, and evolution in interactive systems. The reorientation in our view of interactive systems has been accompanied by a call for a new model of design centered around user needs and participation. This article argues that a new process of design is not enough and that the new view necessitates a similar reorientation in the structure of the systems we build. It outlines some requirements for systems that support a deeper conception of interaction and argues that the traditional system design techniques are not suited to creating such systems. Finally, using examples from ongoing work in the design of an open toolkit for collaborative applications, it illustrates how the principles of computational reflection and metaobject protocols can lead us toward a new model based on open abstraction that holds great promise in addressing these issues.

Groupware toolkits let developers build applications for synchronous and distributed computer-based conferencing. This chapter describes four components that we believe toolkits must provide. A run-time architecture automatically manages the creation, interconnection, and communications of both centralized and distributed processes that comprise conference sessions. A set of groupware programming abstractions allows developers to control the behavior of distributed processes, to take action on state changes, and to share relevant data. Groupware widgets let interface features of value to conference participants be added easily to groupware applications. Session managers let people create and manage their meetings and are built by developers to accommodate the group’s working style. We illustrate the many ways these components can be designed by drawing on our own experiences with GroupKit, and by reviewing approaches taken by other toolkit developers.

Real-time educational groupware systems allow physically separated learners to work together in a shared virtual workspace at the same time. These systems do not yet approach the interaction richness of a face-to-face learning situation. In particular, one element poorly supported is workspace awareness: the up-to-the-minute knowledge a student requires about other students ’ interactions with the shared workspace. This awareness is essential if students are to learn and work together effectively. We present a framework of several types of awareness required by students in a collaborative learning situation, including their social, task, concept and workspace awareness. We then concentrate on workspace awareness, and describe how particular awareness requirements of students in group learning situations depend on the closeness of their tasks, and whether they are sharing the same view or have separate views into the workspace. From these requirements, we have prototyped several awareness widgets for educational groupware. These widgets help learners maintain awareness of other learners ’ locations when their views are separated, of other learners ’ activities in shared and separate view situations, and of other learners ’ past activities.

Gestural communication is an important part of shared work, both in face-to-face settings and distributed environments. However, gestures in groupware are often difficult to see and interpret because of disruptions to their motion caused by network jitter. One way to improve the visibility of remote gestures is by using traces--- visualizations of the last few moments' of a remote pointer's motion. We carried out an experiment to test the effectiveness of traces in helping people interpret gestures. We found that telepointer traces dramatically improved people's accuracy and confidence in their decisions as jitter delays grew larger. Our results suggest that telepointer traces and other visualizations of interaction history can be used to enrich communication among remote collaborators.

This article reports our reflection on software architecture modelling for multi-user systems (or groupware). First, we introduce the notion of software architecture and make explicit the design steps that most software designers in HCI tend to blend in a fuzzy way. Building on general concepts and practice from main stream software engineering, we then present a comparative analysis of the most significant architecture models developed for singleand multi-user systems. We close with the presentation of PAC*, a new architectural framework for modelling and designing the software architecture of multi-user systems. PAC* is a motivated combination of existing architectural models selected for the complementarity of their "good properties". These include operational heuristics such as rules for deriving agents in accordance to the task model or criteria for reasoning about replication, as well as properties such as support for style heterogeneity, portability, and reusability. Keywords ...

This article describes GroupDesign, a multi-user drawing tool that runs in a heterogeneous environment (a network of Apple Macintosh computers and Unix workstations). From the perspective of the users, we present a number of functionalities that we have developed for supporting the collaborative aspect of work and the new user interfaces issues raised by the shared editing of a document: Graphic & Audio Echo, Localization, Identification, Age, History, Teleconference and Private Editing. From the perspective of the designers, we introduce the notion of purely replicated architecture and we describe the tools we have developed to implement this architecture in a heterogeneous environment. We also demonstrate the possibility of creating a multi-user application from a single-user one and address the issues in developing synchronous heterogeneous groupware.

This paper presents a technical approach to building flexible groupware applications. Flexibility provides the promise of personalizable groupware, allowing different groups to work with the system in diverse ways which best suit the group's own needs. An implementation technique called open protocols is described, which is a variation of client/server architectures. Open protocols facilitate the addition of group-specific modules long after the system has been created. Three examples illustrating the use of open protocols are presented: floor control, conference registration, and brainstorming. Finally, a number of issues facing the groupware developer using open protocols are addressed, along with strategies that can help in dealing with these issues. KEYWORDS Personalizable groupware, expandability, open protocols, implementation technique. INTRODUCTION Conventional single-user applications are designed to capture a profitable market share. While the product may not be to everyo...

A great interest has developed in recent years in building tools that allow people to collaborate on work without the need for physical proximity. One such class of tools, group editors, allows collaborators to view and edit a shared document simultaneously from their workstations. Building group editors, however, requires solving non-trivial problems such as providing adequate response time for edit operations and yet ensuring consistency with concurrent updates, and providing adequate per-user undo facilities. We have implemented a toolkit, called DistEdit, for building new interactive group editors and for converting existing single-user editors into group editors with minimal changes to their code. The toolkit allows different users to use their favorite editors (e.g., Xedit, Gnu Emacs) to edit a shared file and observe each others ' changes as they occur. The toolkit provides fine-grain concurrency control, fault-tolerance, synchronization of views, and support for per-user undo. ...

We consider the problem of providing communication protocol support for large-scale group collaboration systems for use in environments such as the Internet which are subject to packet loss, wide variations in end-to-end delays, and transient partitions. We identify a set of requirements that are critical for the design of such group collaboration systems. These include dynamic awareness notifications, reliable data delivery, and scalability to large numbers of users. We present a communication service, Corona, that attempts to meet these requirements. Corona supports two communication paradigms: the publish-subscribe paradigm and the peer group paradigm. We present the interfaces provided by Corona to applications which are based on these paradigms. We describe the semantics of each interface method call and show how they can help meet the above requirements. Keywords CSCW, awareness, groupware, communication services, publish-subscribe, peer group, multicast, Java INTRODUCTION I...

Abstract The World Wide Web is increasingly seen as an attractive technology for the deployment and evaluation of groupware However the underlying architecture of the Web is inherently stateless- best supporting asynchronous types of cooperation This paper presents a toolkit for application developers, MetaWeb, which augments the Web with basic features which provide new and legacy applications with better support for synchronous cooperation. Using three simple abstractions, User, Location and Session, MetaWeb allows applications to be coupled as tightly or as loosely to the Web as desired The paper presents two distinct applications of MetaWeb, including the extension of an existing application, the BSCW shared workspace system, from which a number of observations are drawn 1.