Abstracting Remote Object Interaction in a Peer-2-Peer Environment

Leveraged by the success of applications aiming at the ``free'' sharing of data in the Internet, the paradigm of peer-to-peer (P2P) computing has been devoted substantial consideration recently. This paper presents an abstraction for remote object interaction in a P2P environment, called borrow/lend (BL). We present the principles underlying our BL abstraction, and its implementation in Java. We contrast our abstraction with established abstractions for distributed programming such as the remote method invocation or the tuple space, illustrating how the BL abstraction, obviously influenced by such predating abstractions, unifies flavors of these, but also how it captures the constraints specific to P2P environments

Mobility Friendly Publish/Subscribe

This paper describes an event dissemination algorithm that implements a topic-based publish/subscribe abstraction in mobile ad-hoc networks (MANETs). Our algorithm relies on (1) the mobility of the processes and (2) the validity period of the events to ensure the reliability of the dissemination (under reasonable conditions) with a thrifty usage of the memory. The algorithm is inherently portable and does not assume any specific routing protocol. Old events are collected to save the memory and the energy consumption is, in some sense, related to the size of the event scope a subscriber is interested in. We give simulation results in different mobility models and highlight the advantages/drawbacks of our approach as well as we expose some interesting relations between validity periods and reliability

The Driving Philosophers

We introduce a new synchronization problem in mobile ad-hoc systems: the Driving Philosophers. In this problem, an unbounded number of driving philosophers (processes) access a round-about (set of shared resources organized along a logical ring). The crux of the problem is to ensure, beside traditional mutual exclusion and starvation freedom at each particular resource, gridlock freedom (i.e., cyclic waiting chain amongst processes). The problem captures explicitly the very notion of process mobility and the underlying model does not involve any assumption on the total number of (participating) processes or the use of shared memory, i.e., the model conveys the ad-hoc environment. We present a generic algorithm that solves the problem in a synchronous model. Instances of this algorithm can be fair but not concurrent, or concurrent but not fair. We derive the impossibility of achieving fairness and concurrency at the same time as well as the impossibility of solving the problem in an asynchronous model. We also conjecture the impossibility of solving the problem in an ad-hoc network model with limited-range communication

Data-Aware Multicast

This paper presents a multicast algorithm for peer-to-peer dissemination of events in a distributed topic-based publish-subscribe system, where processes publish events of certain topics, organized in a hierarchy, and expect events of topics they subscribed to. Our algorithm is ``data-aware'' in the sense that it exploits information about process subscriptions and topic inclusion relationships to build dynamic groups of processes and efficiently manage the flow of information within and between these process groups. This ``data-awareness'' helps limit the membership information that each process needs to maintain and preserves processes from receiving messages related to topics they have not subscribed to. It also provides the application with means to control, for each topic in a hierarchy, the trade-off between the message complexity and the reliability of event dissemination. We convey this trade-off through both analysis and simulation

Pragmatic Type Interoperability

Providing type interoperability consists in ensuring that, even if written by different programmers, possibly in different languages and running on different platforms, types that are supposed to represent the same software module are indeed treated as one single type. This form of interoperability is crucial in modern distributed programming. We present a pragmatic approach to deal with type interoperability in a dynamic and distributed environment. Our approach is based on an optimistic transport protocol, specific serialization mechanisms and a set of implicit type conformance rules. We experiment the approach over the .NET platform which we indirectly evaluate

The Driving Philosophers

We introduce a new synchronization problem in mobile ad-hoc systems: the Driving Philosophers. In this problem, an unbounded number of driving philosophers (processes) access a round-about (set of shared resources organized along a logical ring). The crux of the problem is to ensure, beside traditional mutual exclusion and starvation freedom at each particular resource, gridlock freedom (i.e., a cyclic waiting chain among processes). The problem captures explicitly the very notion of process mobility and the underlying model does not involve any assumption on the total number of (participating) processes or the use of shared memory, i.e., the model conveys the ad-hoc environment. We present a generic algorithm that solves the problem in a synchronous model. Instances of this algorithm can be fair but not concurrent, or concurrent but not fair. We derive the impossibility of achieving fairness and concurrency at the same time as well as the impossibility of solving the problem in an asynchronous model. We also conjecture the impossibility of solving the problem in an ad-hoc network model with limited-range communication

Conclusions and consensus statements on periodontal health, policy and education in Europe: A call for action - consensus view 1

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