9,337 research outputs found
Organisational Abstractions for the Analysis and Design of Multi-Agent Systems
The architecture of a multi-agent system can naturally be viewed as a computational organisation. For this reason, we believe organisational abstractions should play a central role in the analysis and design of such systems. To this end, the concepts of agent roles and role models are increasingly being used to specify and design multi-agent systems. However, this is not the full picture. In this paper we introduce three additional organisational concepts - organisational rules, organisational structures, and organisational patterns - that we believe are necessary for the complete specification of computational organisations. We view the introduction of these concepts as a step towards a comprehensive methodology for agent-oriented systems
QoS-Aware Middleware for Web Services Composition
The paradigmatic shift from a Web of manual interactions to a Web of programmatic interactions driven by Web services is creating unprecedented opportunities for the formation of online Business-to-Business (B2B) collaborations. In particular, the creation of value-added services by composition of existing ones is gaining a significant momentum. Since many available Web services provide overlapping or identical functionality, albeit with different Quality of Service (QoS), a choice needs to be made to determine which services are to participate in a given composite service. This paper presents a middleware platform which addresses the issue of selecting Web services for the purpose of their composition in a way that maximizes user satisfaction expressed as utility functions over QoS attributes, while satisfying the constraints set by the user and by the structure of the composite service. Two selection approaches are described and compared: one based on local (task-level) selection of services and the other based on global allocation of tasks to services using integer programming
Distributed Detection and Estimation in Wireless Sensor Networks
In this article we consider the problems of distributed detection and
estimation in wireless sensor networks. In the first part, we provide a general
framework aimed to show how an efficient design of a sensor network requires a
joint organization of in-network processing and communication. Then, we recall
the basic features of consensus algorithm, which is a basic tool to reach
globally optimal decisions through a distributed approach. The main part of the
paper starts addressing the distributed estimation problem. We show first an
entirely decentralized approach, where observations and estimations are
performed without the intervention of a fusion center. Then, we consider the
case where the estimation is performed at a fusion center, showing how to
allocate quantization bits and transmit powers in the links between the nodes
and the fusion center, in order to accommodate the requirement on the maximum
estimation variance, under a constraint on the global transmit power. We extend
the approach to the detection problem. Also in this case, we consider the
distributed approach, where every node can achieve a globally optimal decision,
and the case where the decision is taken at a central node. In the latter case,
we show how to allocate coding bits and transmit power in order to maximize the
detection probability, under constraints on the false alarm rate and the global
transmit power. Then, we generalize consensus algorithms illustrating a
distributed procedure that converges to the projection of the observation
vector onto a signal subspace. We then address the issue of energy consumption
in sensor networks, thus showing how to optimize the network topology in order
to minimize the energy necessary to achieve a global consensus. Finally, we
address the problem of matching the topology of the network to the graph
describing the statistical dependencies among the observed variables.Comment: 92 pages, 24 figures. To appear in E-Reference Signal Processing, R.
Chellapa and S. Theodoridis, Eds., Elsevier, 201
A Non-Cooperative Game Theoretical Approach For Power Control In Virtual MIMO Wireless Sensor Network
Power management is one of the vital issue in wireless sensor networks, where
the lifetime of the network relies on battery powered nodes. Transmitting at
high power reduces the lifetime of both the nodes and the network. One
efficient way of power management is to control the power at which the nodes
transmit. In this paper, a virtual multiple input multiple output wireless
sensor network (VMIMO-WSN)communication architecture is considered and the
power control of sensor nodes based on the approach of game theory is
formulated. The use of game theory has proliferated, with a broad range of
applications in wireless sensor networking. Approaches from game theory can be
used to optimize node level as well as network wide performance. The game here
is categorized as an incomplete information game, in which the nodes do not
have complete information about the strategies taken by other nodes. For
virtual multiple input multiple output wireless sensor network architecture
considered, the Nash equilibrium is used to decide the optimal power level at
which a node needs to transmit, to maximize its utility. Outcome shows that the
game theoretic approach considered for VMIMO-WSN architecture achieves the best
utility, by consuming less power.Comment: 12 pages, 8 figure
A value chain and cluster perspective on competitiveness of European fresh vegetable production â Case studies from Germany, Italy, and Spain
In the present study we combine cluster theory with a value chain approach, with the aim of discovering elements of the European fresh vegetable business that could enable local producers to gain competitive advantages in a global market. European producers of fresh vegetables are under pressure to improve their performance and increase their competitiveness. Competitive advantage can be gained through innovation and by using unique resources stemming from cooperation between producers and complementary actors in local clusters. However, locally clustered producers do not sell to open markets but need access to value chains governed by lead firms, the large European retail chains, which set the rules and conditions of participation. The study presents first results from a multiple case-study analysis involving three different European regions in Germany, Italy and Spain specialized in fresh vegetable production. In-depth interviews with practitioners allowed us to confirm some main trends in business organization in the European fresh vegetable industry, but also to point out some interesting peculiarities of this industry. Local fresh vegetable producers become competitive due to their integration both in local production and wider marketing networks, where unique knowledge is created and interchanged by personal relationships. Further concentration on the local level is claimed to countervail power imbalances that usually favor buyers. The need for leading supermarket chains to build up direct relationships with key suppliers disturbs the functioning of existing relationship patterns in the local cluster. Creation of exclusive relationships with retail chains is pursued by entrepreneurs of innovative producing farms who treat their special knowledge and capacities as competitive advantages in the sharp competition in world markets and do not share it with other cluster actors.Fresh vegetables, value chains, clusters, competitiveness
Distributed Web Service Coordination for Collaboration Applications and Biological Workflows
In this dissertation work, we have investigated the main research thrust of decentralized coordination of workflows over web services. To address distributed workflow coordination, first we have developed âWeb Coordination Bondsâ as a capable set of dependency modeling primitives that enable each web service to manage its own dependencies. Web bond primitives are as powerful as extended Petri nets and have sufficient modeling and expressive capabilities to model workflow dependencies. We have designed and prototyped our âWeb Service Coordination Management Middlewareâ (WSCMM) system that enhances current web services infrastructure to accommodate web bond enabled web services. Finally, based on core concepts of web coordination bonds and WSCMM, we have developed the âBondFlowâ system that allows easy configuration distributed coordination of workflows. The footprint of the BonFlow runtime is 24KB and the additional third party software packages, SOAP client and XML parser, account for 115KB
- âŠ