LINC: A Compact Yet Powerful Coordination Environment

International audienceThis paper presents LINC, a coordination programming environment. It is an evolution of earlier middlewares (the Coordination Language Facility (CLF) and Stitch). The aim is to provide a more flexible and expressive language correcting several of their limitations and an improved run-time environment. LINC provides a compact yet powerful coordination language and an optimised run-time which executes rules. This paper describes the intrinsic properties brought by the LINC environment and how it helps the coordination aspects in a distributed system. This paper also emphasises on the reflexivity of LINC and its usage at system level. Finally, it illustrates through several case studies, how LINC can manage a wide range of application domains

Concepts et mécanismes pour la mise en oeuvre d'un environnement d'édition coopérative sur un réseau à grande échelle

The following dissertation addresses one aspect of cooperative editing which has not been well examined until now : the consideration of hardware limitations imposed by a large scale distributed system (namely the Internet). This system model implies heterogeneous hardware, unbounded communication delays, and process failures. In this context, mechanisms usually used for cooperative editing in a local area network are not suitable. The model proposed here is based on a dynamic decomposition of the document into independant parts, maintained by a replicated kernel. The decomposition is controlled by the users themselves, who can then act on the concurrency allowed at the document level. The more a document is fragmented, the more concurrency is allowed. The replication of the independant document parts within the kernel, ensures the document availability and this regardless of the performances of the users' sites. Communication is reduced to minimum, thus allowing use in large scale distributed system. Users interact with the kernel either by copying a kernel object to their own local environment where it can be modified, or by handling over the modified object to the kernel. Consistency is managed according to several policies that can be chosen by the user depending on the document maturity or the required interaction with the other users. A new criterion has been defined to ensure consistency : the NRT-linearizability. This criterion is more adapted to our problem than linearizability, and allows in particular a non-blocking implementation even in the case of failures (user site as well as kernel site failure), which is important when considering large scale distributed system. This criterion maintains the locality property of the linearizability. Contrary to the classical approach, this criterion is not applied to the read-modify-write operations ensuring the atomicity of the following actions : loading a document part into an editor, modifying it with the editor, and storing the modified part. The atomicity of the read-modify-write operations is only considered ot the application level and takes into account the knowledge of the users. Thus, the user is free to choose the way it will be performed His her choice will be made between several concurrency control policies based on rules established between the users, either optimistic based on conflict detection, pessimistic based on capabilities, or hybrid

Reliable Control through Wireless Networks

submitted paperReliability is one of the biggest challenges when using Wireless Sensor-Actuator Networks in control systems. This paper exploits the transactional guarantees offered by the LINC coordination environment to provide reliability and robustness in wireless control systems. First, LINC transactions were embedded in the mirco-controllers to deal with possible communication errors, faulty devices, and concurrent access to the devices. Then, an active replication mechanism was provided so that the system can be correctly recovered from hardware and communication failures. A case study of a ball and plate problem is detailed. The plate is lift up and down by three motors. Each motor is controlled by a micro-controller communicating in wireless with the system controller

Rapid prototyping of complete systems, the case study of a smart parking

International audienceThis paper details how LINC a coordination middle-ware, can fasten the development of prototypes that integrate several equipment. A case study of rapid prototyping is presented. It illustrates how a smart parking prototype has been built from several independent and autonomous equipment, coming from different vendors. This has been achieved by parallel development thanks to the resource based approach offered by LINC. This paper also describes how LINC helps building rich user interfaces quickly and easily. I. INTRODUCTION Embedded systems have been part of our daily life for decades. Most of the industrial or consumer products embed multiple processors, sensors and actuators. The next step is the opportunity to build new products, systems, and usages, combining together several of these products. In such innovative and quickly evolving context it is necessary to build prototypes to test, validate, and challenge new products usages or solutions. This paper considers prototypes including several equipment, possibly from different vendors. Such prototypes can be used to exhibit demonstrations in a trade fair, to convince investors of the viability of an idea or to verify the adequacy of the solutions for early adopters. To succeed in today's highly competitive market, a prototype should be more than a few items wired together with a command line interface. Targeted prototypes are real-life demonstrations of new products or technologies with a high end-user experience. Moreover, a prototype should be included in its targeted environment (e.g. a house, a building or a parking). The development of prototypes is vital during the validation stage of new products as they may help to

Smart Sensors and Actuators: A Question of Discipline

Low power consumption and reliability are two important properties in the wireless sensor network area. The approach presented here to improve these aspects is to use a rule-based middleware enforcing a coordination protocol on top of the communication protocols imposed by the different wireless sensor networks. In addition, we move the callee side of this protocol from the gateway to the sensors/actuators in order to make them able to directly respond to this protocol. Then, it is possible to control from the application side the control (sleep/awake) of the sensors and the transactional processing of operations involving a group of sensors/actuators. This has a positive impact both on the consumption and the reliability. Examples illustrating our approach are presented

Preconditioning of the Reduced System Associated with the Restricted Additive Schwarz Method

International audienceIt is of interest to solve large scale sparse linear systems on distributed computers, using Krylov subspace methods along with domain decomposition methods. If accurate subdomain solutions are used, the restricted additive Schwarz preconditioner allows a reduction to the interface via the Schur complement, which leads to an unpreconditioned reduced operator for the interface unknowns. Our purpose is to form a preconditioner for this interface operator by approximating it as a low-rank correction of the identity matrix. To this end, we use a sequence of orthogonal vectors and their image under the interface operator, which are both available after some iterations of the generalized minimal residual method

Duplex: A Distributed Collaborative Editing Environment in Large Scale

DUPLEX is a distributed collaborative editor for users connected through the Internet. Large scale implies heterogeneity, unpredictable communication delays, and failures, and leads to inefficient implementations of techniques traditionally used for collaborative editing in local area networks. To cope with these unfavorable conditions, DUPLEX proposes a model based on splitting the document into independent parts, maintained individually and replicated by a kernel. Users act on document parts and interact with co-authors using a local environment providing a safe store and recovery mechanisms against failures or divergence with co-authors. Communication is reduced to a minimum, allowing disconnected operation. Atomicity, concurrency, and replica control are confined to a manageable small context. KEYWORDS: Collaborative editing, distributed groupware, large scale networks, concurrency control INTRODUCTION The past ten years have seen the number of interconnected computers and networ..