Recent developments in information technology have brought about important changes in distributed computing. New environments such as massively large-scale, wide-area computer networks and mobile ad hoc networks have emerged. Common characteristics of these environments include extreme dynamicity, unreliability, and large scale. Traditional approaches to designing distributed applications in these environments based on central control, small scale, or strong reliability assumptions are not suitable for exploiting their enormous potential. Based on the observation that living organisms can effectively organize large numbers of unreliable and dynamically-changing components (cells, molecules, individuals, etc.) into robust and adaptive structures, it has long been a research challenge to characterize the key ideas and mechanisms that make biological systems work and to apply them to distributed systems engineering. In this article we propose a conceptual framework that captures several basic biological processes in the form of a family of design patterns. Examples include plain diffusion, replication, chemotaxis, and stigmergy. We show through examples how to implement important functions for distributed computing based on these patterns. Using a common evaluation methodology, we show that our bio-inspired solutions have performance comparable to traditional, state-of-the-art solutions while they inherit desirable properties of biological systems including adaptivity and robustness.

As computers are increasingly used for communicating information, multimedia has become an important component of interactive applications.Effective communication with multimedia requires tight media integration, highly interactive control over multimedia, and the use of multimedia to support group interactions.This paper shows how the MVC paradigm for user interface development can be extended to support temporal media.The resulting framework allows easy specification of media-integrated interactive applications, including multimedia groupware.All examples in this paper have been implemented in Clock, a novel programming environment, and run on IBM, SGI, and Sun workstations.

The Model View Controller (MVC) architecture has proven to be an effective way of organizing synchronous groupware applications. Distributed implementations of MVC, however, can suffer from poor performance. This paper demonstrates how optimized semi-replication of MVC architectures can lead to good performance over both local and wide area networks. We present a series of optimizations to network communication based on specific communication properties of groupware. These optimizations have been implemented in the Clock groupware development toolkit, allowing programmers to develop applications directly in the high-level MVC style, with Clock automatically providing optimized performance. Timings of an application developed in Clock show that usable speed was obtained in a highly interactive groupware application running between Toronto and Calgary, with a typical latency of 190 ms per round trip message. The paper discusses the tradeoffs involved in the algorithms, and presents timings to demonstrate the effectiveness of the different approaches. The timings show that when running over a wide area network, the best optimization can achieve a factor 60 speedup over the naive implementation of distributed MVC.

Multi-user applications support multiple users performing a related task in a distributed context. This paper describes Weasel, a system for implementing multi-user applications. Weasel is based on the relational view model, in which user interfaces are specified as relations between program data structures and views on a display. These relations are specified in RVL, a high-level, declarative language. Under this model, an application program and a set of RVL specifications are used to generate a multi-user application in which all issues of network communication, concurrency, synchronization, and view customization are handled automatically. These programs have a scalable distribution property, where adding new participants to a session does not greatly degrade over-all system performance. Weasel has been implemented, and was used to generate all examples in this paper.