On the Expressiveness of Linda-like Concurrent Languages

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On the Introduction of Guarded Lists in Bach: Expressiveness, Correctness, and Efficiency Issues

Concurrency theory has received considerable attention, but mostly in the scope of synchronous process algebras such as CCS, CSP, and ACP. As another way of handling concurrency, data-based coordination languages aim to provide a clear separation between interaction and computation by synchronizing processes asynchronously by means of information being available or not on a shared space. Although these languages enjoy interesting properties, verifying program correctness remains challenging. Some works, such as Anemone, have introduced facilities, including animations and model checking of temporal logic formulae, to better grasp system modelling. However, model checking is known to raise performance issues due to the state space explosion problem. In this paper, we propose a guarded list construct as a solution to address this problem. We establish that the guarded list construct increases performance while strictly enriching the expressiveness of data-based coordination languages. Furthermore, we introduce a notion of refinement to introduce the guarded list construct in a correctness-preserving manner.Comment: In Proceedings ICE 2023, arXiv:2308.0892

Environmental Good Production in the Optimum Activities Portfolio of a Risk Averse Farmer

An analytical framework is proposed for analysis of environmental good production by farmers in the case of price uncertainty. Environmental good production contracted by means of agri-environmental agreements is treated as a risk less option in the farmer's production activities portfolio. Efficient frontiers were generated using mathematical programming farm level models of suckler cow farms in Monts du Cantal, in France. It was demonstrated that for a DARA risk averse farmer: 1) the agreement payment level is not without impact on the farming intensity on parcels not subscribed under the corresponding argi-environmental programme, 2) a lump sum payment matters under uncertainty, 3) the overall impact of the lump sum payment on environmental good production depends on the type of jointness in production of agricultural and environmental goods, and on the level of uncertainty.uncertainty, portfolio optimisation, biodiversity, agricultural policy, mathematical programming, Agricultural and Food Policy, Resource /Energy Economics and Policy, Q12, Q18, Q28,

On Modeling Coordination via Asynchronous Communication and Enhanced Matching

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Environmental good production in the optimum activities portfolio of a risk averse-farmer

An analytical framework is proposed for analysis of environmental good production by farmers in the case of price uncertainty. Environmental good production contracted by means of agri-environmental agreements is treated as a riskless option in the farmer’s production activities portfolio. It is shown that agri-environmental agreements aiming at biodiversity competing with beef production are likely to increase management intensity on the non-enrolled land, and that the effect of the payments for these agreements on the number of hectares enrolled is ambiguous. It is also demonstrated that an increase in the output price variability and/or a decrease in the level of decoupled subsidies will induce an increase (decrease) in the area enrolled in agreements aiming at biodiversity competing with (complementary to) beef production. The obtained results are illustrated by means of efficient frontiers generated using mathematical programming farm level models of suckler cow farms in Monts du Cantal, in France.uncertainty, portfolio optimisation, biodiversity, agricultural policy, mathematical programming

Blackboard Rules for Coordinating Context-aware Applications in Mobile Ad Hoc Networks

Thanks to improvements in wireless communication technologies and increasing computing power in hand-held devices, mobile ad hoc networks are becoming an ever-more present reality. Coordination languages are expected to become important means in supporting this type of interaction. To this extent we argue the interest of the Bach coordination language as a middleware that can handle and react to context changes as well as cope with unpredictable physical interruptions that occur in opportunistic network connections. More concretely, our proposal is based on blackboard rules that model declaratively the actions to be taken once the blackboard content reaches a predefined state, but also that manage the engagement and disengagement of hosts and transient sharing of blackboards. The idea of reactiveness has already been introduced in previous work, but as will be appreciated by the reader, this article presents a new perspective, more focused on a declarative setting.Comment: In Proceedings FOCLASA 2012, arXiv:1208.432

3D simulations of gas puff effects on edge density and ICRF coupling in ASDEX Upgrade

In recent experiments, a local gas puff was found to be an effective way to tailor the scrape-off layer (SOL) density and improve the ion cyclotron range of frequency (ICRF) power coupling in tokamaks. In order to quantitatively reproduce these experiments, to understand the corresponding physics and to optimize the gas valve positions and rates, simulations were carried out with the 3D edge plasma transport code EMC3-EIRENE in ASDEX Upgrade. An inter-ELM phase of an H-mode discharge with a moderate gas puff rate (1.2 x 10(22) electrons s(-1)) is used in our simulations. We simulated cases with gas puff in the lower divertor, the outer mid-plane and the top of the machine while keeping other conditions the same. Compared with the lower divertor gas puff, the outer mid-plane gas puff can increase the local density in front of the antennas most effectively, while a toroidally uniform but significantly smaller enhancement is found for the top gas puff. Good agreement between our simulations and experiments is obtained. With further simulations, the mechanisms of SOL density tailoring via local gas puffing and the strategies of gas puff optimization are discussed in the paper