36 research outputs found

    The design of a protocol for collaboration in a distributed repository - Nomad

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    Computer Supported Cooperative Work (CSCW) is the study of how people use technology, with relation to hardware and software, to work together in shared time and space. Mobile office environments are becoming commonplace. Workers form virtual online communities on a global scale and use groupware to collaborate and complete a common goal. We tend to be mobile, yet need to be available to collaborate. This thesis investigates a protocol for our decentralized artifact control system, Nomad. Nomad enables globally dispersed members of small casually connected communities to share artifacts which are gathered on a best effort approach. The Nomad protocol takes into consideration the work habits of users and their variety of devices. The major contribution of this thesis is a simulator of the Nomad protocol, which serves as a proof-of-concept for its design. Specifically, we look at how such a protocol handles casually connected small communities. We consider high level aspects such as setting up the community, the overhead of nodes, availability, scalability and connectivity. We demonstrate scenarios that the protocol will need to handle. Furthermore, we take a broad look at CSCW, push and pull technologies, peer-to-peer technologies, and enabling technologies such as Microsoft .Net. These form the basis of the Nomad design. In addition, we suggest the integration of mobile agents, which we consider a future addition to Nomad. It was found that the protocol had to compensate for two nodes that were never online at the same time. In the case that a best effort approach is not feasible, we propose alternate approaches at the cost of overhead on a propagation node. The developed concept provided valuable insight into the problem domain, outlined the boundaries of the protocol and provided a possible solution for Nomad. The simulator proved to be a useful tool for determining outcomes from possible scenarios. The results from the simulator will feed directly into the development of Nomad.Dissertation (MSc (Computer Science))--University of Pretoria, 2007.Computer Scienceunrestricte

    Network architecture for collaborative distributed services

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    Thesis (S.M.)--Massachusetts Institute of Technology, School of Architecture and Planning, Program in Media Arts and Sciences, 2005.Includes bibliographical references (p. 85-89).This thesis proposes a network architecture, called SMPL, for the design and development of collaboration-oriented, distributed applications over the Internet. The goal of SMPL is to enable the development of applications that easily integrate the capabilities of different types of computing resources, software platforms, and data repositories across the Internet transcending the level of a single device. SMPL proposes a new abstraction of the Internet as a network composed of services, resources, and capabilities instead of just machines. The SMPL architecture distributes resources through a peer-to-peer network of service providers. The design of SMPL encourages developers to add value to the system by facilitating the creation of new functionalities based upon compositions of the existing ones.Carlos A. Rocha.S.M

    D-CaseLP: un ambiente distribuito per l\u27integrazione di Agenti Eterogenei.

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    It concerns the design of a rapid prototyping environment to ease the development of Multi-Agent Systems taking into account the declarative properties of logic programming paradigm and FIPA specification

    Designing and experimenting coordination primitives for service oriented computing

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    Service Oriented Architecture (SOA) and Web Services (WS) are becoming a widely accepted device for designing and implementing distributed systems. SOAs have given an important contribution to software engineering providing a model where applications are defined by assembling together certain functionalities, called services, possibly provided by remote suppliers. The characterizing issue of SOAs consists of defining common principles to make services accessible and usable regardless their execution context. Nevertheless, the architectural specification is far from giving a complete reference application model on which systems should rely on. The specification just includes principles for achieving interoperability and reusability of services; other aspects are left to the implementing platforms. As a consequence, it is understood how services are specified in isolation and how their functionalities are made available to the requesters, but the definition of languages for describing service composition are far from being widely accepted and reveals to be an impelling challenge. In the last years, several solutions have been proposed for describing aggregated services. However, they often lack a formally defined semantics. Moreover, these solutions are often specific for a platform (e.g. WSs) and are difficult to adapt to other platforms since they rely on low level assumptions that are out of the SOA specifications. This thesis aims at providing new methodologies for implementing the coordination of services. Our framework proposes to be flexible enough to support high level languages and to provide reliable tools for testing correctness of implementation. Our approach relies on a formal model that takes the form of a process calculus specifically designed to deal with services and their coordination. The process calculus has been the main tool driving the specification issues as well the implementation issues. Indeed, it acts as a bridge between the high level specification language and the run-time environment. A distinguished feature of our proposal is that our formal model, i.e. the process calculus, describes distributed processes relying on an event notification mechanism as machinery for interactions. Services are represented by certain components that embody local computations and react to changes of the overall environment in which they are involved. The adoption of event notification results particularly fashionable for tackling service coordination. The principles studied at specification level are from one side understood within a theoretical framework that provides instruments for checking correctness of interaction policies and from the other side offers the core model for implementing and experimenting a programming middleware

    Parallel Processes in HPX: Designing an Infrastructure for Adaptive Resource Management

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    Advancement in cutting edge technologies have enabled better energy efficiency as well as scaling computational power for the latest High Performance Computing(HPC) systems. However, complexity, due to hybrid architectures as well as emerging classes of applications, have shown poor computational scalability using conventional execution models. Thus alternative means of computation, that addresses the bottlenecks in computation, is warranted. More precisely, dynamic adaptive resource management feature, both from systems as well as application\u27s perspective, is essential for better computational scalability and efficiency. This research presents and expands the notion of Parallel Processes as a placeholder for procedure definitions, targeted at one or more synchronous domains, meta data for computation and resource management as well as infrastructure for dynamic policy deployment. In addition to this, the research presents additional guidelines for a framework for resource management in HPX runtime system. Further, this research also lists design principles for scalability of Active Global Address Space (AGAS), a necessary feature for Parallel Processes. Also, to verify the usefulness of Parallel Processes, a preliminary performance evaluation of different task scheduling policies is carried out using two different applications. The applications used are: Unbalanced Tree Search, a reference dynamic graph application, implemented by this research in HPX and MiniGhost, a reference stencil based application using bulk synchronous parallel model. The results show that different scheduling policies provide better performance for different classes of applications; and for the same application class, in certain instances, one policy fared better than the others, while vice versa in other instances, hence supporting the hypothesis of the need of dynamic adaptive resource management infrastructure, for deploying different policies and task granularities, for scalable distributed computing

    Uma interface para refinamento de pesquisas de políticas de segurança em ambientes de grid services

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    Dissertação (mestrado) - Universidade Federal de Santa Catarina, Centro Tecnológico. Programa de Pós-Graduação em Ciência da Computação.A computação em grid (ou computação em grade) consiste em uma forma de computação distribuída onde o foco principal é o compartilhamento coordenado de recursos em larga escala e resolução de problemas em organizações virtuais dinâmicas e multi-institucionais. Porém, tal compartilhamento deve ser altamente controlado, para garantir a segurança dos recursos envolvidos. Este trabalho se baseia na especificação OGSA (Open Grid Service Architecture) proposta pelo GGF (Global Grid Forum), em particular no Globus Toolkit 3 que a implementa, e apresenta uma proposta de extensão ao módulo de monitoramento e descoberta de recursos (MDS), para filtrar os resultados retornados baseado nos atributos do usuário e nas políticas do recurso

    Redes de próxima geração: uma visão funcional

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    Show a description of the convergence technologies, that if it initiated with the net of traditional telephony commuted by circuit, where served of base for the first convergent services. It is intended, also, to explain as it is the current scene of the Nets of Next Generation with reference the evolution to the nets, the convergence, the compatibility of the broadband versus mobility, in view of that the user is "a devorador" potential of width of band, for in such a way, the technological convergence will give itself through xTecnologias on IP, this monograph will show to aspects of the IPv6 protocol with regard to its perationalization and addressing. E still topical of the application of Open Architecture of Services since the operators study a form to open its "doors" for the suppliers, making partnerships with intention to increase the use of its resources. The user will present aspects of the implementation of an intelligent environment where does not go to be worried about the sophisticated devices of interconnection and the some types of nets. This work, also, intends to mostar some excellent topics that must be weighed for the diverse segments of the companies of telecommunications as: the necessities from final users, of the suppliers of services and the suppliers of nets. The following pages will present, still, considerações regarding suppliers and services with regard to profiles of users, models of business and terminals of access, as well as, aspects with relation to the technology of physical access, mobile access and fixed access wireless, and also, excellent topics on the Y.2001 Recommendation, that offers a general vision on net NGN, according to ITU-T. It intends to present excellent topics between the NGN and the X.200 recommendation, that if it relates to the Basic Model of Reference - OSI. E, considerações regarding service finally multimedia to be fit by net NGN, as well as, of the interoperabilidade between environments NGN and not NGN regarding the quality of service and a conclusion regarding that it was presented.Demonstra um histórico das tecnologias de convergência, que se iniciou com a rede de telefonia tradicional comutada por circuito, onde serviu de base para os primeiros serviços convergentes. Pretende-se, também, explicar como está o cenário atual das Redes de Próxima Geração com referência a evolução das redes, a convergência, a compatibilidade da banda passante versus mobilidade, tendo em vista que o usuário é um potencial “devorador” de largura de banda, para tanto, a convergência tecnológica se dará através de xTecnologias sobre IP, esta monografia mostrará aspectos do protocolo IPv6 com relação a sua operacionalidade e endereçamento. E ainda tópicos da aplicação de Arquitetura Aberta de Serviços já que as operadoras estudam uma forma de abrir suas “portas” para os provedores, fazendo parcerias com o intuito de aumentar a utilização de seus recursos. Apresentará aspectos da implementação de um ambiente inteligente aonde o usuário não vai se preocupar com os sofisticados dispositivos de interconexão e os vários tipos de redes. Este trabalho, também, pretende mostrar alguns tópicos relevantes que devem ser ponderados pelos diversos segmentos das empresas de telecomunicações como: as necessidades a partir de usuários finais, dos provedores de serviços e dos provedores de redes. As páginas seguintes apresentarão, ainda, considerações a respeito de provedores e serviços com relação a perfis de usuários, modelos de negócio e terminais de acesso, bem como, aspectos com relação à tecnologia de acesso físico, acesso móvel e acesso wireless fixo, e também, tópicos relevantes sobre a Recomendação Y.2001, que oferece uma visão geral sobre a rede NGN, segundo a ITUT. Pretende apresentar tópicos relevantes entre a NGN e a recomendação X.200, que se refere ao Modelo de Referência Básico - OSI. E por fim, considerações a respeito de serviço multimídia a ser enquadrado pela rede NGN, bem como, da interoperabilidade entre ambientes NGN e não NGN a respeito da qualidade de serviço e uma conclusão a respeito do que foi apresentado

    A distributed information sharing collaborative system (DISCS)

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    Combining SOA and BPM Technologies for Cross-System Process Automation

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    This paper summarizes the results of an industry case study that introduced a cross-system business process automation solution based on a combination of SOA and BPM standard technologies (i.e., BPMN, BPEL, WSDL). Besides discussing major weaknesses of the existing, custom-built, solution and comparing them against experiences with the developed prototype, the paper presents a course of action for transforming the current solution into the proposed solution. This includes a general approach, consisting of four distinct steps, as well as specific action items that are to be performed for every step. The discussion also covers language and tool support and challenges arising from the transformation

    Hypermedia-based Web Services as System Integrators

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    As we move more closely to the practical concept of the Internet of Things and, our reliance on public and private APIs increases, web services and their related topics have become utterly crucial to the informatics community. However, the question about which style of web services would best solve a particular problem, can raise signi cant and multifarious debates. There can be found two implementation styles that highlight themselves: the RPC-oriented style represented by the SOAP protocol’s implementations and the hypermedia style, which is represented by the REST architectural style’s implementations. As we search examples of already established web services, we can nd a handful of robust and reliable public and private SOAP APIs, nevertheless, it seems that RESTful services are gaining popularity in the enterprise community. For the current generation of developers that work on informatics solutions, REST seems to represent a fundamental and straightforward alternative and even, a more deep-rooted approach than SOAP. But are they comparable? Do both approaches have each speci c best suitable scenarios? Such study is brie y carried out in the present document’s chapters, starting with the respective background study, following an analysis of the hypermedia approach and an instantiation of its architecture, in a particular case study applied in a BPM context.Devido ao facto de estarmos cada vez mais próximos do conceito prático de Internet of Things, assim como da nossa dependência em APIs públicas e privadas estar a aumentar, o tópico de web services e outros tópicos relacionados tornam-se bastante cruciais para a comunidade dedicada à área informática. Pode-se encontrar dois tipos principais de estilos de implementação que se destacam: o estilo orientado a RPC, cujo conceito é representado pelas implementações do protocolo SOAP e o estilo hypermedia representado pelas implementações do estilo arquitetural REST. Ao procurarmos exemplos de web services estabelecidos no mercado, é possível nos depararmos com várias APIs SOAP públicas e privadas classi cadas como robustas e áveis. No entanto, aparentemente, os serviços cujas implementações são orientadas ao estilo arquitetural REST, estão a ganhar popularidade na comunidade empresarial. Para a geração atual de developers que trabalham em soluções informáticas, REST aparenta ser uma alternativa mais essencial, direta e até sólida que SOAP. Mas será que são comparáveis? Será que cada abordagem tem o seu cenário de melhor enquadramento? O estudo presente neste documento tenta responder a este tipo de questões, começando com um estudo do background correspondente, seguido de uma analise da abordagem hypermedia e uma instanciação da sua arquitetura, num caso de estudo aplicado num contexto BPM
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