1,721,106 research outputs found
From tuple spaces to tuple centres
No full textA tuple centre is a tuple space whose behaviour can be defined by means of reactions to communication events. In this paper, we motivate and define the notion of tuple centre, both conceptually and formally. Then, we show how adopting a tuple centre for the coordination of a multiagent system can benefit both the system design and the overall system performance. © 2001 Elsevier Science B.V. All rights reserved
Formal ReSpecT
No full textLogic-based languages have already proved to be effective to build individual agents and to enable inter-agent communication in multi-agent systems. Also, logic tuple centres have shown that logic-based languages can be effectively exploited to rule inter-agent communication so as to build social behaviours. In this paper, we formally define the notion of logic tuple centre as well as the operational semantics of the logic-based language ReSpecT for the behaviour specification of logic tuple centres. For this purpose, we exploit a formal framework for asynchronous systems allowing coordination media to be represented in a separate and independent way with respect to the coordinated entities. As a by-product, this shows that a logic-based approach may be effectively exploited for the coordination of heterogeneous agents of different sorts and technologies. ©2001 Published by Elsevier Science B. V
LuCe: A Tuple-based Coordination Infrastructure for Prolog and Java Agents
No full textThe engineering of an application as a multi-agent system (MAS henceforth) calls
for models, languages, and tools specifically tailored to the metaphors of agent and
agent society. In these systems, agents are typically required to interact and interoperate, yet this is not enough to guarantee that the MAS operates towards the
accomplishments of its global goals: what is needed is the ability of constraining
interaction so as to ensure that the social rules of the MAS, intended as an agent
society, are respected and enforced. This is what coordination is for. In order to provide standard metaphors and abstractions to build agent societies,
coordination should be one of the basic services supplied by an effective infrastructure for MAS design, development and run-time support. LuCe is a coordination infrastructure providing MAS engineers with tuple-based coordination technology for both Prolog and Java agents. Based on logic tuple centres, LuCe enables the definition of (reusable) intelligent coordination components, and effectively supports the MAS construction process by model-specific tools, which bring the model metaphors to action
An architecture for tuple-based coordination of multi-agent systems
No full textMulti-agent system development calls for powerful and expressive coordination models and languages, as well as for an effective coordination technology. A good deal of the current research effort focuses on tuple-based coordination, exploiting its well-known advantages, such as agent uncoupling and associative access to information, and addressing its limitations in terms of flexibility and control capabilities. In particular, the behaviour of a Linda-like tuple space is fixed once and for all by the coordination model, and cannot be tailored to the specific application needs. Tuple centres are tuple spaces whose behaviour can be programmed by defining transactional reactions to the basic communication events, allowing coordination laws to be explicitly defined and embedded into the coordination medium. This paper presents the architecture of a run-time system for tuple-based coordination, where tuple centres work as an extensible kernel, around which multi-agent systems can be designed and deployed. After sketching the implementation, the paper shows the advantages that can be achieved from both the design and the performance viewpoints
Optimal in-orbit repositioning of Sun-pointing Smart Dust
Full text linkA Smart Dust is a femto-spacecraft with an external surface coated with electrochromic material, which exploits the solar radiation pressure to produce a propulsive acceleration. As the optical properties of the electrochromic material change upon application of a suitable electric voltage, its propulsive acceleration may be modulated, within some limits, without the use of any propellant. This paper analyzes the optimal trajectories of a Sun-pointing Smart Dust, which provides a propulsive acceleration aligned with the Sun-spacecraft direction. In particular, the paper describes the relative motion of a Smart Dust with respect to a conventional spacecraft (the Mother Ship) that covers a heliocentric circular orbit of given radius. The Smart Dust is required to vary periodically its angular position with respect to the Mother Ship using an optimal (minimum time) strategy. This problem is addressed using an indirect approach and the optimal control law is obtained in a closed-form solution. The results discussed in this paper ensure interesting improvements over existing models from the recent literature, including the possibility of obtaining a generic phasing angle of the Smart Dust and to take into account an optimal number of on-off switchings of the electrochromic control system
Connessione denti e impianti: Analisi della letteratura
No full textScopo del lavoro: La riabilitazione mista su denti e impianti presuppone una condizione di parziale edentulia e l’impossibilità di sostituire ogni singolo elemento con un impianto. La complicanza più frequentemente descritta di questa terapia protesica è rappresentata dall’intrusione a scapito del pilastro naturale, la cui causa, secondo la maggior parte degli autori, risiederebbe nella fisiologica differenza di mobilità fra impianto e dente. Scopo del presente contributo è analizzare, in base agli studi longitudinali, le indicazioni al trattamento misto e il diverso comportamento dei due pilastri protesici, dente e impianto. Conclusioni Il successo a lungo termine dipende da alcune considerazioni relative alla situazione anatomica, all’utilizzo di una connessione rigida per evitare l’intrusione del dente, al fatto che gli elementi parodontalmente compromessi e con mobilità elevata non dovrebbero essere uniti rigidamente agli impianti; alla biomeccanica della connessione mista, che può causare il distacco della protesi cementata; e al fatto che, se la protesi è avvitata, la vite si può allentare o fratturare all’interno della corona
Virtual enterprises and workflow management as agent coordination issues
No full textAgents and multiagent systems (MAS) have already proved suitable for dealing with the complexity of today B2B application scenarios. Application environments such as virtual enterprises (VE) and inter-organizational workflow management systems (WfMS) specially call for the integration of heterogeneous resources, services, and processes. In this article, we first recognize VE and workflow management as agent coordination problems, then discuss how objective coordination - that is, coordination from outside agents - can help to model VE and WfMS. Finally, we show the impact of an agent coordination infrastructure like TuCSoN on the engineering of highly dynamic VE and WfMS, by discussing a simple case study
Coordination tools for mas development and deployment
No full textOne of the most critical issues in the engineering of multi-agent systems (MAS) is the inadequacy of the available tools for MAS development and deployment. As we assume interaction as a first-class issue in MAS, tools are particularly required to monitor and debug inter-agents aspects, such as interaction protocols, coordination policies, social norms, and environment constraints. Since we claim that the definition of such tools is a basic research issue, in this paper we aim to identify the main requirements for development and deployment tools within an effective agent infrastructure. Focusing on agent interaction aspects, we take tuple-based coordination infrastructures - in particular the TuCSoN technology and tools - as our reference, and discuss the role of tools in a simple case study: the development and deployment of a well-known agent interaction protocol, the Contract Net
Relative Motion of Sun-pointing Smart Dust in Circular Heliocentric Orbits
Full text linkThe aim of thisNote is to extend the results of [12] to the study of the linearized relative motion of a sun-pointing SD and an MS when the latter describes a circular heliocentric orbit. More precisely, assuming the sun–SD distance to be close to the MS orbital radius, the linearized relative dynamics between SD and MS is described with an approach similar to that used by McInnes in the analysis of the azimuthal repositioning problem for a solar sail-based spacecraft.
The contribution in the study to follow is therefore different from that discussed in [12], whose aim, instead, is to find the SD heliocentric trajectory as a function of a given control law. The results about the SD–MS relative dynamics are obtained in an analytical form and are applied to a phasing mission case, a scenario in which the SD varies its angular position (along the circular reference orbit) with respect to that of the MS
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