Implementing atomic rendezvous within a transactional framework

International audienceThe authors address the problem of implementing the CSP (communicating sequential processes) rendezvous within a transactional framework. Instead of implementing a fair nondeterministic choice and assuming the correct functioning of processors and communication media, the authors propose an efficient transactional implementation of the atomic rendezvous in the presence of processor failures in a multiprocessor machine. Both atomicity and efficiency are obtained by using high-speed stable storage device

Increasing Data Resilience of Mobile Devices with a Collaborative Backup Service

Whoever has had his cell phone stolen knows how frustrating it is to be unable to get his contact list back. To avoid data loss when losing or destroying a mobile device like a PDA or a cell phone, data is usually backed-up to a fixed station. However, in the time between the last backup and the failure, important data can have been produced and then lost. To handle this issue, we propose a transparent collaborative backup system. Indeed, by saving data on other mobile devices between two connections to a global infrastructure, we can resist to such scenarios. In this paper, after a general description of such a system, we present a way to replicate data on mobile devices to attain a prerequired resilience for the backup

An experimental study of Java objects behaviour for mobile architectures

Java is an interesting programming language in the context of embedded applications for the flexibility and security it provides. However, its execution requirements and performances are often an issue. We plan to build a better Java execution environment, targeting mobile phones. To improve its performances, we believe that a special attention has to be put on the mapping of Java objects in memory. To understand the issues, an overview of memory inside a standard Java Virtual Machine is proposed. Then, relevant characteristics and behaviours of objects from selected embedded applications are presented. Their similarities with standard desktop applications are also illustrated, along with a first discussion on how they could be organized on memory

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

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PERSEND : Enabling Continuous Queries in Proximate Environments

In the mobile computing area, short-range wireless communication technologies enable to envision direct interactions between mobile devices.Thus, each device can be provided with a remote access to data its neighbours agree to share. Such a service enables applications to consult a set of data providers which dynamically evolves according to the mobility of the neighbouring devices. The set of data sources an application may access by this way is therefore representative of its physical neighbourhood. For this purpose, we propose to design a tool enabling the continuous consultation of neighbouring shared data. We present, in this paper, the PERSEND system we develop in this scope. Based on relational databases systems, PERSEND enables applications to define continuous queries over neighbouring data

Using Context to Combine Virtual and Physical Navigation

In this paper we present how context can be used to support an user that is navigating both virtually and physically an information system. Navigation is seen as the act of going from one object to another. Navigation can be virtual like the Web navigation or physical like with a digital museum guide. We start by giving a formal definition of context that relies on the notion of proximity. An important peculiarity of this definition is that it permits us to build context according to several dimensions at a time, like the thematic dimension, the physical dimension or the temporal dimension. This definition permits us to build two applications that ease the navigation by constantly proposing relevant destinations to the navigating user. The first application is an assistant to help an user that navigates the web. The second application is a digital guide that permits the user to navigate through an information system composed of digital photos

Increasing Data Resilience of Mobile Devices with a Collaborative Backup Service

Whoever has had his cell phone stolen knows how frustrating it is to be unable to get his contact list back. To avoid data loss when losing or destroying a mobile device like a PDA or a cell phone, data is usually backed-up to a fixed station. However, in the time between the last backup and the failure, important data can have been produced and then lost. To handle this issue, we propose a transparent collaborative backup system. Indeed, by saving data on other mobile devices between two connections to a global infrastructure, we can resist to such scenarios. In this paper, after a general description of such a system, we present a way to replicate data on mobile devices to attain a prerequired resilience for the backup

Dependability of Aggregated Objects, a pervasive integrity checking architecture

International audienceRFID-enabled security solutions are becoming ubiquitous; for example in access control and tracking applications. Well known solutions typically use one tag per physical object architecture to track or control, and a central database of these objects. This architecture often requires a communication infrastructure between RFID readers and the database information system. Aggregated objects is a different approach presented in this paper, where a group of physical objects use a set of RFID tags to implement a self-contained security solution. This distributed approach offers original advantages, in particular autonomous operation without an infrastructure support, and enhanced security

Communicating processes and fault tolerance : a shared memory multiprocessor experience

The concept of backward recovery is now well established as a means of restoring a consistent state of a fault tolerant system should some faults occur. In this paper, we consider a system of communicating processes mapped onto a multilevel execution support. A shared memory multiprocessor machine is assumed. Our interest is in tolerating the hardware faults that may occur during the execution of a concurrent computation. The machine provides a hardware backard recovery protocol based on a specialized memory device which tracks dependencies between the processors accessing shared data residing in memory. The transparency provided by the protocol is discussed considering successively the models of computation at the various levels of abstraction of the execution support

Lessons from FTM: an Experiment in the Design and Implementation of a Low Cost Fault Tolerant System

This report describes an experiment in the design of a general purpose fault tolerant system, FTM. The main objective of the FTM design was to implement a "low-cost" fault tolerant system that could be used on standard workstations. At the operating system level, our goal was to provide a methodology for the design of modular reliable operating systems, while offering fault tolerance transparency to user applications. In other words, porting an application to FTM had only to require compiling the source code without having to modify it. These objectives were achieved using the Mach micro-kernel and a modular set of reliable servers which implement application checkpoints and provide continuous system functions despite machine crashes. At the architectural level, our approach relies on a high performance stable storage implementation, called Stable Transactional Memory (STM), which can be implemented either by hardware or software. We first motivate our design choices, then we detail the FTM implementation at both architectural and operating system level. We comment on the reasons for the evolution of our stable memory technology from hardware to software. Finally, we present a performance evaluation of the FTM prototype. We conclude with lessons learned and give some assessments