445 research outputs found

    KLAIM: A Kernel Language for Agents Interaction and Mobility

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    We investigate the issue of designing a kernel programming language for mobile computing and describe KLAIM, a language that supports a programming paradigm where processes, like data, can be moved from one computing environment to another. The language consists of a core Linda with multiple tuple spaces and of a set of operators for building processes. KLAIM naturally supports programming with explicit localities. Localities are first-class data (they can be manipulated like any other data), but the language provides coordination mechanisms to control the interaction protocols among located processes. The formal operational semantics is useful for discussing the design of the language and provides guidelines for implementations. KLAIM is equipped with a type system that statically checks access rights violations of mobile agents. Types are used to describe the intentions (read, write, execute, etc.) of processes in relation to the various localities. The type system is used to determine the operations that processes want to perform at each locality, and to check whether they comply with the declared intentions and whether they have the necessary rights to perform the intended operations at the specific localities. Via a series of examples, we show that many mobile code programming paradigms can be naturally implemented in our kernel language. We also present a prototype implementaton of KLAIM in Java

    A coordination language for mobile components

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    Abstract In this paper we present the sigmapi coordination language, a core language for specifying dynamic networks of components. The language is inspired by the Manifold coordination language and by the pi-calculus. The main concepts of the language are components, classes, objects and channels. A program in sigmapi consists of a number of components, where each component is a collection of classes separable from its original context and re-usable in any other context. An object is an instance of a class that executes in parallel with the other objects active in the system. The sigmapi language differs from other models of object-oriented systems mainly in its treatment of communication and mobility: communication is anonymous via synchronous or asynchronous channels, while mobility is obtained by moving channels in the virtual space of linked objects. Thus, a channel is a transferable capability of communication, and objects are mobile in the sense that their communication possibilities may change during a computation. The language sigmapi itself does not impose exogenous coordination, meaning that the coordination primitives affecting each object can be executed within the computation of the object itself. However, only simple restrictions on the class-definitions of a sigmapi program suffice to enforce a separation between computation and coordination. Interaction typically occurs anonymously and under the full control of the objects involved. This make it easier to deal with Internet application where security policies must be enforced in view of the possibilities of attacks

    A coordination language for mobile components

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    The mobile agent technology to support and to access museum information

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    Who gets the information? Gender, power and equity considerations in the design of climate services for farmers

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    Central to understanding the usefulness of climate and weather forecasts in support of agricultural decision-making is addressing the issue of who receives what information. Many contend that improved climate forecasts since the late 1990s have had limited impact on smallholder farming communities in Africa and across the developing world. However, power and privilege may determine who has access to appropriate climate and advisory services within those communities. In 2011-2012, we tested this hypothesis in three climate-vulnerable farming communities in the CGIAR Research Program on Climate Change, Agriculture and Food Security semi-arid research site of Kaffrine, Senegal. Therein, we assessed gender-specific vulnerabilities to climate-related shocks, endogenous adaptation strategies, and coping mechanisms. From the gap between vulnerability and local capacity, we deduced farmers’ climate service needs, and then assessed whether these systematically differed between distinct vulnerable sub-groups within the community – chiefly, between male and female farmers. In 2011 we introduced a seasonal climate forecast for the first time in the community, and explored perceptions of forecast access, usefulness and value, by both men and women

    KLAIM: a kernel language for agents interaction and mobility

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    Active citizenship and participation through the media: a community project focused on pre-school and primary school children

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    The project “Educação para a cidadania digital e participação democrática” [Digital citizenship education for democratic participation], which began in 2015, currently involves around 200 kindergarten and primary school children, their families, teachers and other members of the Caneças educational community, a neighbourhood in Odivelas, Lisbon. The project’s methodology is action research, its objective is to understand how a coordinated action by a school, families and the community, contributes to enabling three to nine-year-old children to become active digital citizens. This paper focuses on social participation activities of children through traditional and digital media and involves activities that include formal, non-formal and informal learning contexts. Results show that social participation of children through the media increased and gradually evolved from producing traditional media content (school newspaper) to producing digital content (video). They also evidence that action research methodology, adjusted to context and deriving from prior understanding of the context, is an adequate methodology for developing this type of project. However, its adequate implementation implies the support of the school board, researchers’ support to the teachers and the involvement of journalists and/or other media professionals.O projeto “Educação para a cidadania digital e participação democrática” envolveu cerca de 200 crianças de Pré-escolar e 1º Ciclo, suas famílias, professoras e outros membros das comunidades escolar e educativa de Caneças, concelho de Odivelas, distrito de Lisboa. Assumindo como metodologia a investigação-ação, teve como objetivo central compreender em que medida uma ação concertada da escola, das famílias e da comunidade contribui para a preparação de crianças, dos três aos nove anos, para o exercício de uma cidadania digital ativa. Este artigo centra-se nas atividades de participação social das crianças, através dos média, tradicionais e digitais, envolvendo atividades marcadas pela transversalidade entre os contextos de aprendizagem formais, não-formais e informais. Os resultados mostram que a participação social das crianças através dos média aumentou, tendo evoluído paulatinamente, da produção de conteúdos de média tradicionais (jornal escolar) para a produção de conteúdos digitais (vídeo). Revelam ainda que um modelo de investigação-ação, efetivamente adaptado ao contexto e em função da prévia caracterização deste, é uma metodologia adequada ao desenvolvimento deste tipo de projetos. Mas o adequado desenvolvimento implica ainda apoio da direção da escola, apoio sustentado dos investigadores aos docentes e o desejável envolvimento de jornalistas e/ou outros profissionais de média

    Cooperative team formation using distributed decomposition knowledge

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    In recent years, the problem of automating the formation of Virtual Organisations (VO) has risen to prominence. Work in this area has typically considered the process of VO formation to be a centralised process driven by a company with responsibility for the business opportunity.Such systems use two main stages: first they decompose the business opportunity into a set of roles and then select suppliers for each role by matching their advertised capability against criteria supplied by the user. Both stages require that the company driving the VO formation process has access to considerable amounts of centralised knowledge.In contrast, this thesis considers virtual organisations as forming by combining the cooperative contributions within a group of organisations. It is shown that, within this context, both the knowledge required to facilitate and the control within the virtual organisation formation process are naturally distributed. In particular companies are free to vary their level of commitment to given projects and so only they have detailed knowledge of their capabilities. Supporting VO formation within this context requires a novel approach capable of utilising this distributed information. The primary contribution of this thesis is to provide such a novel approach to supporting virtual organisation formation. This approach builds on the traditions of blackboard and multi-agent systems. It allows virtual organisation formation to be driven by the accumulation of voluntary contributions from the prospective members of the virtual organisation. The principle focus of the system is on identifying candidate virtual organisations, and it does not offer automated support for such aspects as the creation of contracts. Crucially this system works with the distributed knowledge encountered in the chosen problem domain. The following technical contributions shape the general approach into a detailed system: (a) the representation of company's capabilities, (b) an algorithm for combining those capabilities and (c) mechanisms enabling intelligent agents representing the companies to produce candidate virtual organisations. The proposed system is evaluated in three ways - its technical feasibility is demonstrated through the implementation of a testbed prototype, a theoretical discussion of the systems performance is given and finally its potential benefits are shown in a reasoned case study.EThOS - Electronic Theses Online ServiceGBUnited Kingdo
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