Summary form only given. The amount of information available from electronic sources on the World Wide Web and other on-line information repositories is highly heterogeneous and increasing dramatically. Tools are needed to extract relevant information from these repositories. The Constraint-Based Knowledge Brokers project (CBKB) at RXRC Grenoble realizes sophisticated facilities for efficient information retrieval, schema integration, and knowledge fusion. The current implementation of the CBKB research prototype involves three kinds of agents: a) users, who input queries and process answers (i.e., ranking, fusion) through a GUI; b) wrappers, capable of interrogating heterogeneous information sources, which can provide answers to elementary queries (essentially various public bibliographic catalogues available on the Web, as well as preprint archives and opera information repositories); c) brokers, which can manage complex queries (i.e., decompose a complex query, recompose the partial answers, synthesize a full answer) and which mediate between the GUI and the different wrappers. The core of the system is given by the brokers, which provide various important services such as intelligent caching, filtering and knowledge combination. Requests, intermediate information, and results are internally represented via feature constraints. Requests do not need to be fully defined; they may correspond to partial specifications of the requested information.

Abstract This paper presents a system for constructing collaborative design applications based on distributed augmented reality. Augmented reality interfaces are a natural method for presenting computer‐based design by merging graphics with a view of the real world. Distribution enables users at remote sites to collaborate on design tasks. The users interactively control their local view, try out design options, and communicate design proposals. They share virtual graphical objects that substitute for real objects which are not yet physically created or are not yet placed into the real design environment. We describe the underlying augmented reality system and in particular how it has been extended in order to support multi‐user collaboration. The construction of distributed augmented reality applications is made easier by a separation of interface, interaction and distribution issues. An interior design application is used as an example to demonstrate the advantages of our approach.

The purpose of the Guide project is to explore the use of shared objects for communication in a distributed system, especially for applications that require cooperative work. Since 1986, two prototypes have been implemented respectively on top of Unix (Guide-1) and Mach 3.0 (Guide-2). They have been used for the development of distributed cooperative applications, allowing us to validate or reject many design choices in the system.

The design and implementation of a replicated object server called Goofy, which is intended to provide a fault-tolerant storage system for distributed object-oriented applications, are described. Goofy supplies the object storage of the GUIDE (Grenoble Universities Integrated Distributed Environment) distributed object-oriented system with integrity, reliability and availability, while preserving object consistency despite network partition failures. Some preliminary experiments are described. Goofy is compared with related work on replicated servers, and the lessons drawn from this work and some conclusions on fault tolerance in GUIDE are given.>