Michel Banâtre

The design and building of Enchère, a distributed electronic marketing system

Building and prototyping an agricultural electronic marketing system involved experimenting with distributed synchronization, atomic activity, and commit protocols and recovery algorithms.

Ubibus: Ubiquitous Computing to Help Blind People in Public Transport

Ubibus is an application designed to help blind or visually impaired people to take public transport. The application allows the user to request in advance the bus of his choice to stop, and to be notified when the right bus has arrived. The user may use either a PDA (equipped with a WLAN interface) or a Bluetooth mobile phone.

Design, implementation and evaluation of ICARE: an efficient recoverable DSM

In the light of the increasing throughput of local area networks, Networks Of Workstations (NOWs) which provide a Distributed Shared Memory (DSM) have become a convenient and cheaper alternative to parallel architectures in the framework of parallel scientific applications. However, the probability that a failure occurs in such a system made up of a large number of components must not be neglected, especially for long‐running applications. This paper presents the design, implementation and performance evaluation of ICARE, a page‐based recoverable DSM implemented on top of an ATM‐based NOW running the CHORUS microkernel. ICARE relies on a Backward Error Recovery (BER) mechanism, and provides a way to combine both efficiency and high‐availability. The fact that checkpoints are stored in volatile memory provides a low‐cost fault‐tolerance mechanism, as well as the opportunity to exploit the symbiotic relationship between the data replication implemented in DSM systems and that needed for fault‐tolerance. Furthermore, ICARE efficiently implements transparent process rollback recovery. Performance evaluations show the efficiency of the ICARE prototype that implements the proposed algorithms.

Memory Management for Real-Time Java: An Efficient Solution using Hardware Support

This paper addresses the issue of improving the performance of memory management for real-time Java applications, building upon the real-time specification for Java (RTSJ) from the Real-Time Java Expert Group. In a first step, a collecting dynamic memory solution including both a real-time garbage collector and region-based memory management, is proposed. A thorough analysis of the parameters influencing the performance of write barriers in memory management, together with ways of improvement are then presented. Finally, the implementation of a memory management solution compliant with the RTSJ and integrating the proposed improvements is sketched.

Collaborative backup for dependable mobile applications

We describe the work we are conducting on new middleware services for dependable and secure mobile systems. This work is based on approaches à la peer-to-peer in order to circumvent the problems introduced by the lack of infrastructure in self-organizing networks of mobile nodes, such as MANETs. The mechanisms we propose are based on collaboration between peer mobile devices to provide middleware services such as trust management and critical data storage. This short paper gives a brief description of the problems we are trying to solve and some hints and ideas towards a solution.

Providing quality of service over the Web: a newspaper-based approach

The long-term success of the World Wide Web depends on the provided quality of service. Users need to be confident about the quality of the information that they are accessing and to have the selected information displayed within a short interval. This paper gives an overview of the ETEL newspaper-based distributed information system, subset of the World Wide Web, that meets the above requirement. The ETEL system guarantees relevance of the information through moderation by a newspaper editor. It further ensures responsiveness through the provision of dedicated system policies, implementing in particular predictive prefetching.

Using context to navigate through a photo collection

In this article we present an application to navigate through a photo collection, using context. This application proposes two navigation schemes: physical and virtual navigation. Physical navigation permits the user to seamlessly access to photos that were taken near him. Virtual navigation permits the user to virtually explore the surroundings by jumping from one photo to another.This application relies on a definition of context which is based on a notion of proximity. Proximity can be determined according to one or several dimensions. For example, with this definition the users context can be represented by the photos that were taken near him during a precise period like the Second World War. Such a context permits the user to physically navigate the photo collection nowadays and to get photos of the surroundings that were taken during another time period. Our application offers other services, such as temporal navigation to get different views of a place, route planing or virtually entering into closed buildings.

A New Protocol for Efficient Cooperative Transversal Web Caching

The bandwidth demands on the World Wide Web continue to grow at an exponential rate. To address this problem, many research activities are focusing on the design of Web caches. Unfortunately, Web caches exhibit poor performance with a hit rate of about 30%. A solution to improve this rate, consists of groups of cooperating caches. In its most general form, a cooperative cache system includes protocols for hierarchical and transversal caching. Although such a system brings better performance, its drawback lies in the resulting network load due to the number of messages that need to be exchanged to locate an object. This paper introduces a new protocol for transversal cooperative caching, which significantly reduces the associated network load compared to that induced by existing systems. ...

Tolerating node failures in cache only memory architectures

COMAs (cache only memory architectures) are an interesting class of large scale shared memory multiprocessors. They extend the concepts of cache memories and shared virtual memory by using the local memories of the nodes as large caches for a single shared address space. Due to their large number of components, these architectures are particularly susceptible to hardware failures and so fault tolerance mechanisms have to be introduced to ensure a high availability. We propose an implementation of backward error recovery in a COMA which minimizes performance degradation and requires little hardware modifications. This implementation uses the features of a COMA to implement a stable storage abstraction using the standard memories of the architecture. Recovery data are replicated and mixed with current data in node memories both of which are managed in a transparent way using an extended coherence protocol.<<ETX>>

Improving the Effectiveness of Web Caching

The bandwidth demands on the (World-Wide) Web continue to grow at an exponential rate. It is thus becoming crucial to provide solutions improving the Web latency. In that framework, the most promising low cost solution lies in the use of caches at the level of the clients, network and servers. Caching effectiveness then relies upon adequate cache management so as to keep in the cache the Web objects that are the most likely to be re-accessed. However, the effectiveness of a single cache remains poor as it is in general no higher than 40%. One way to further improve caching effectiveness is thus to make caches cooperate so as to increase the probability of retrieving an object at the caching level. The cache cooperation protocol must then be such that it induces a negligible load for the network and cooperating caches. This paper presents our solutions to improving the effectiveness of Web caching concerning both cache management and cache cooperation. Regarding cache management, we propose two novel algorithms that exploit the latest results about Web usage, enabling us to undertake replacement decisions that are more accurate than the one taken by existing algorithms. From the standpoint of cooperating caches, we propose a cooperation protocol, which minimizes the associated network bandwidth, processing load, and storage consumption among caches.