Simon M. Kaplan

A High Performance Totally Ordered Multicast Protocol

This paper presents the Reliable Multicast Protocol (RMP). RMP provides a totally ordered, reliable, atomic multicast service on top of an unreliable multicast datagram service such as IP Multicasting. RMP is fully and symmetrically distributed so that no site bears an undue portion of the communication load. RMP provides a wide range of guarantees, from unreliable delivery to totally ordered delivery, to K-resilient, majority resilient, and totally resilient atomic delivery. These QoS guarantees may be selected on a per packet basis. RMP provides many communication options, including virtual synchrony, a publisher/subscriber model of message delivery, a client/server model of delivery, an implicit naming service, mutually exclusive handlers for messages, and mutually exclusive locks.

Physical spaces, virtual places and social worlds: a study of work in the virtual

Through a case study of a group of systems administrators, we explore the nature of collaborative work when that work is carried out in virtual workspaces. This study shows the many ways that work in the virtual is different to work in the physical domain. Through it, we suggest a new interpretation of spatial metaphors for the design and construction of collaborative systems based on the notion of ‘place’ or ‘locale’, and on centres rather than boundaries. We use the observation that people work in multiple social worlds simultaneously, that these social worlds provide an abstract structuring over the virtual work domain, and that the individual will draw from this structure those elements relevant to their many tasks.

Flexible, active support for collaborative work with ConversationBuilder

Work activities have a highly situated nature. As a result, it is not possible to classify activities exactly, since they tend to evolve as they progress. This raises a significant problem for work support tools: how to address the trade off between active support, which requires knowledge of the activity at hand, and flexibility, which is a measure of how well a system can respond to changes in activities. We have been developing the ConversationBuilder, a support tool that is intended to provide flexible, active support for (collaborative) work activities. This paper overviews the ConversationBuilder, discusses both the kinds of support it provides and its architecture, and illustrates its use through an example.

Augmenting the workaday world with Elvin

This paper addresses the problem of providing effective, computer-based support for awareness and interaction in the distributed workaday world We report the story of how our content-based pure notification service, called Elvin, became widely adopted in our organisation and elsewhere, augmenting the virtual work environment, and providing perceptual resources for awareness. Examples of its uses include support for interaction via bi-directional chat-like facilities as well as support for uni-directional notifications, for example push-based information from services such as WWW and email, and notifications of the activities of others through rooms bookings, version control changes, and so on. These uses have had a significant impact on the way people interact with information sources and on social cohesion within the organisation. The attraction of Elvin lies in its conceptual simplicity, absence of built-in policy, expressive power and multilingual range of simple APIs. Its uptake is largely a result of the Tickertape Elvin client, which provides a simple, compelling interface usable in numerous different situations. We contend that even though it does not try to be a collaboration-friendly notification service, Elvin is paradoxically very useful for collaborative awareness and interaction support.

Supporting Public Availability and Accessibility with Elvin: Experiences and Reflections

We provide a retrospective account of how a generic event notification service called Elvin and a suite of simple client applications: CoffeeBiff, Tickertape and Tickerchat, came to be used within our organisation to support awareness and interaction. After overviewing Elvin and its clients, we outline various experiences from data collated across two studies where Elvin and its clients have been used to augment the workaday world to support interaction, to make digital actions visible, to make physical actions available beyond the location of action, and to support content and socially based information filtering. We suggest there are both functional and technical reasons for why Elvin works for enabling awareness and interaction. Functionally, it provides a way to produce, gather and redistribute information from everyday activities (via Elvin) and to give that information a perceptible form (via the various clients) that can be publicly available and accessible as a resource for awareness. The integration of lightweight chat facilities with these information sources enables awareness to easily flow into interaction, starting to re-connect bodies to actions, and starting to approximate the easy flow of interaction that happens when we are co-located. Technically, the conceptual simplicity of the Elvin notification, the wide availability of its APIs, and the generic functionality of its clients, especially Tickertape, have made the use of the service appealing to developers and users for a wide range of uses.

Evolving Orbit: a process report on building locales

The worlds project at the DSTC is experimenting with computer-based collaboration support. Our goal is to provide support for the workaday activities of distributed groups. To facilitate this we are in parallel developing a theory of collaborative activity (the locales framework) and a series of prototypes to test this theory. In this paper we briefly overview the theory and then describe the evolution of the three versions of our Orbit prototype. The prototypes focus on providing a range of facilities, including shared distributed objects, multiple personalizable views, user-controllable presence and awareness of user activities, and the ability to participate in multiple activities simultaneously, with varying degrees of intensity.

Multiuser, Distributed Language-Based Environments

How do you keep teams of programmers informed of system changes without burying them in mail messages? Make the environment responsible for propagating changes.

Supporting collaborative processes with ConversationBuilder

Abstract Conversation Builder is a collaborative open system which can be tailored to support group activities in specialized domains of application. In particular we are interested in supporting collaborative processes, i.e. those activities performed by groups such that the actions of one individual in turn impacts the possibilities for action of the other group members. This paper discusses the concept of collaborative processes and the theoretical basis for Conversation Builder, as well as outlining the architecture of the system and illustrating its use through an example.

Component-based software systems for smart environments

The article focuses on the role component-based software may play in realizing smart environments. A scenario describes a future smart environment in a university campus setting. The scenario illustrates how software components might contribute to the various phases of development, deployment and use of smart environments. Key research areas identified include: development of component frameworks, component interface standards, addressing schemes, and protocols.

Designing support for remote intensive-care telehealth using the locales framework

We put forward the locales t%wnework as a model for the principled understanding and analysis of systems support for cooperative work situations. By using the locales framework to identify problems and issues with existing practice and focus discussion on possible solutions, we can articulate requirements for systems design. This is illustrated through a study of interand intra-ICU consultation practice across three hospital intensive care units (ICUS). By applying the fkunework to the analysis of existing local and remote work practices, we evolve a family of requirements for a telecommunications-based remote consultation facility, sketch its high-level design and discuss the current status of the project.