is a PhD candidate in the electrical engineering department at Stanford University and is one of the student leads in the interactive workspaces project. His research interests include genetic programming, computer networking, and computer graphics. He received a BA in computer science and a BS in electrical engineering and computer science from Cornell University, an MS in computer science from the University of Birmingham in England, and an MS in electrical engineering from Stanford University. Contact him at bjohanso@graphics.stanford.edu.Armando Fox is an assistant professor at Stanford University. His research interests include systems approaches to improving dependability and system software support for ubiquitous computing. He received a BS in electrical engineering from MIT, an MS in electrical engineering from the University of Illinois, and a PhD in electrical engineering from the University of California at Berkeley. He is a member of the ACM and a founder of ProxiNet (now a division of PumaTech), which commercialized the thin client mobile computing technology he helped develop at UC Berkeley. Contact him at fox@cs.stanford.edu.Terry Winograd is a professor of computer science at Stanford University, where he directs the interactivity laboratory and the program in human-computer interaction design. He is one of the principal investigators in the Stanford digital libraries project and the interactive workspaces project. His research interests include human-computer interaction design, with a focus on the theoretical background and conceptual models. Contact him at winograd@cs.stanford.edu. the AUTHORS

Abstract. Coordinating the interactions of applications running on the diversity of devices that will be common in ubiquitous computing environments is still a difficult and not completely solved problem. We look at one such environment, an interactive workspace, where groups come together to collaborate on solving problems. Such a space will contain a heterogeneous collection of both new and legacy applications and devices. We propose that a tuplespace model with several extensions is ideal for coordination in this environment. We present a prototype implementation of such a model called the Event Heap. Finally, we show that the system has performed well in actual use over the last year and a half in our prototype interactive workspace, the iRoom.

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The current interest in programming models and software infrastructures to support ubiquitous and environmental computing is heightened by the falling cost of hardware and the ubiquity of local-area wireless networking technologies. Interactive workspaces are technologically augmented team-project rooms that represent a specific sub-domain of ubiquitous computing. We argue both from related work and from our own experience with a prototype that the tuplespace model of communication forms the best basis for a coordination infrastructure for such workspaces. This paper presents the usage and characteristics expected of interactive workspaces, from which we derive a set of key system properties for any coordination infrastructure in an interactive workspace. We show that the design aspects of tuplespaces, augmented with some new extensions, yield a system model, which we call the Event Heap, that satisfies all of the desired properties. We also briefly discuss why other coordination models fall short of the desired properties, and describe our experience using our implementation of the Event Heap model. The paper focuses on a justification of the use of tuplespaces in interactive workspaces, and does not provide a detailed discussion of the Event Heap implementation or our more general experience with interactive workspaces, each of which is treated in detail elsewhere.

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