74,570 research outputs found

    Dynamic deployment of web services on the internet or grid

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    PhD ThesisThis thesis focuses on the area of dynamic Web Service deployment for grid and Internet applications. It presents a new Dynamic Service Oriented Architecture (DynaSOAr) that enables the deployment of Web Services at run-time in response to consumer requests. The service-oriented approach to grid and Internet computing is centred on two parties: the service provider and the service consumer. This thesis investigates the introduction of mobility into this service-oriented approach allowing for better use of resources and improved quality of service. To this end, it examines the role of the service provider and makes the case for a clear separation of its concerns into two distinct roles: that of a Web Service Provider, whose responsibility is to receive and direct consumer requests and supply service implementations, and a Host Provider, whose role is to deploy services and process consumers' requests on available resources. This separation of concerns breaks the implicit bond between a published Web Service endpoint (network address) and the resource upon which the service is deployed. It also allows the architecture to respond dynamically to changes in service demand and the quality of service requirements. Clearly defined interfaces for each role are presented, which form the infrastructure of DynaSOAr. The approach taken is wholly based on Web Services. The dynamic deployment of service code between separate roles, potentially running in different administrative domains, raises a number of security issues which are addressed. A DynaSOAr service invocation involves three parties: the requesting Consumer, a Web Service Provider and a Host Provider; this tripartite relationship requires a security model that allows the concerns of each party to be enforced for a given invocation. This thesis, therefore, presents a Tripartite Security Model and an architecture that allows the representation, propagation and enforcement of three separate sets of constraints. A prototype implementation of DynaSOAr is used to evaluate the claims made, and the results show that a significant benefit in terms of round-trip execution time for data-intensive applications is achieved. Additional benefits in terms of parallel deployments to satisfy multiple concurrent requests are also shown

    Dynamic Mashup Interfaces for Information Systems using Widgets-as-a-Service

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    Web Information Systems intend to adapt to the users’ preferences as new data available on the network. In this regard, the composition and reuse of services which are involved in a web application is an interesting research topic, since these techniques pursue the dynamic construction of applications that can be adapted at design or run time. As for the visualization of these applications, web user interfaces play a key role, serving as a connection point between users and the rest of the system. This article proposes an architecture for specification, storage, management and visualization of components, built from widgets complying with the W3C recommendation, for making web user interfaces. We follow a service-based approach for the interface deployment and communication management, introducing the concept of Widgets-as-a-Service (WaaS). To illustrate this proposal, an example of widget-based Web Information System is shown

    Economic Policy Analysis and the Internet: Coming to Terms with a Telecommunications Anomaly

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    The significant set of public policy issues for economic analysis that arise from the tensions between the ‘special benefits’ of the Internet as a platform for innovation, and the drawbacks of the “anomalous” features of the Internet viewed as simply one among the array of telecommunications systems, is the focus of discussion in this chapter. Economists concerned with industrial organization and regulation (including antitrust and merger law) initially found new scope for application of their expertise in conventional policy analyses of the Internet’s interactions with other segments of the telecommunications sector (broadcast and cable television, radio and telephone), and emphasized the potential congestion problems posed by user anonymity and flat rate pricing. Policy issues of a more dynamic kind have subsequently come to the fore. These involve classic tradeoffs between greater efficiency and producer and consumer surpluses today, and a potential for more innovation in Web-based products and service in the future. Many such tradeoffs involve choices such as that between policies that would preserve the original ‘end-to-end’ design of the original Internet architecture, and those that would be more encouraging of market-driven deployment of new technologies that afforded ISPs with greater market power the opportunity to offer (and extract greater profits from) restricted-Web services that consumers valued highly, such as secure and private VOIP.public policy, telecommunications, Web-based products, user anonymity

    A Chemistry-Inspired Workflow Management System for a Decentralized Composite Service Execution

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    With the recent widespread adoption of service-oriented architecture, the dynamic composition of such services is now a crucial issue in the area of distributed computing. The coordination and execution of composite Web services are today typically conducted by heavyweight centralized workflow engines, leading to an increasing probability of processing and communication bottleneck and failures. In addition, centralization induces higher deployment costs, such as the computing infrastructure to support the workflow engine, which is not affordable for a large number of small businesses and end-users. Last but not least, central workflow engines leads to diverse inadequate consequences dealing with privacy or energy consumption. In a world where platforms are more and more dynamic and elastic as promised by cloud computing, decentralized and dynamic interaction schemes are required. Addressing the characteristics of such platforms, nature-inspired analogies recently regained attention to provide autonomous service coordination on top of dynamic large scale platforms. In this report, we propose a decentralized approach for the execution of composite Web services based on an unconventional programming paradigm that relies on the chemical metaphor. It provides a high-level execution model that allows executing composite services in a fully decentralized manner. Composed of services communicating through a persistent shared space containing control and data flows between services, our architecture allows to distribute the composition among nodes without the need for any centralized coordination. A proof of concept is given, through the deployment of a software prototype implementing these concepts, showing the viability of an autonomic vision of service composition.Suite Ă  l'adoption grandissante des architectures orientĂ©es service, la composition dynamique de services est devenu un problĂšme important de la construction de plates-formes de calcul distribuĂ©. La coordination et l'exĂ©cutiuon de Web Service composites sont aujourd'hui typiquement conduits par des moteurs de "workflows" (graphes de composition de services, formant un "service composite") centralisĂ©s, entrainant diffĂ©rents problĂšmes, et notamment une probabilitĂ© grandissante d'apparition d'Ă©checs ou de goulots d'Ă©tranglement. Dans un monde oĂč les plate-formes sont de plus en plus dynamiques (ou "Ă©lastiques", comme envisagĂ© par les "clouds", de nouveaux mĂ©canismes de coordination dynamiques sont requis. Dans ce contexte, des mĂ©taphores naturelles ont gagnĂ© une attention particuliĂšre rĂ©cemment, car elles fournissent des abstractions pour la coordination autonome d'entitĂ©s (commes les services.) Dans ce rapport, une approche dĂ©centralisĂ©e pour l'exĂ©cution de Web Services composites fondĂ©e sur la mĂ©taphore chimique, qui fournit un modĂšle d'exĂ©cution haut-niveau pour l'exĂ©cution dĂ©centralisĂ©e, est prĂ©sentĂ©e. Dans cette architecture, les services communiquent Ă  travers un espace virtuellement partagĂ© persistant contenant l'information sur les flux de contrĂŽle et de donnĂ©es, permettant une coordination dĂ©centralisĂ©e des services. Un prototype logiciel a Ă©tĂ© dĂ©veloppĂ© et expĂ©rimentĂ©. Les rĂ©sultats de ces expĂ©riences sont prĂ©sentĂ©s Ă  la fin de ce rapport

    Dynamic Model-based Management of Service-Oriented Infrastructure.

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    Models are an effective tool for systems and software design. They allow software architects to abstract from the non-relevant details. Those qualities are also useful for the technical management of networks, systems and software, such as those that compose service oriented architectures. Models can provide a set of well-defined abstractions over the distributed heterogeneous service infrastructure that enable its automated management. We propose to use the managed system as a source of dynamically generated runtime models, and decompose management processes into a composition of model transformations. We have created an autonomic service deployment and configuration architecture that obtains, analyzes, and transforms system models to apply the required actions, while being oblivious to the low-level details. An instrumentation layer automatically builds these models and interprets the planned management actions to the system. We illustrate these concepts with a distributed service update operation

    An architecture for autonomic web service process planning

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    Web service composition is a technology that has received considerable attention in the last number of years. Languages and tools to aid in the process of creating composite web services have been received specific attention. Web service composition is the process of linking single web services together in order to accomplish more complex tasks. One area of web service composition that has not received as much attention is the area of dynamic error handling and re-planning, enabling autonomic composition. Given a repository of service descriptions and a task to complete, it is possible for AI planners to automatically create a plan that will achieve this goal. If however a service in the plan is unavailable or erroneous the plan will fail. Motivated by this problem, this paper suggests autonomous re-planning as a means to overcome dynamic problems. Our solution involves automatically recovering from faults and creating a context-dependent alternate plan

    An Infrastructure for the Dynamic Distribution of Web Applications and Services

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    This paper presents the design and implementation of an infrastructure that enables any Web application, regardless of its current state, to be stopped and uninstalled from a particular server, transferred to a new server, then installed, loaded, and resumed, with all these events occurring "on the fly" and totally transparent to clients. Such functionalities allow entire applications to fluidly move from server to server, reducing the overhead required to administer the system, and increasing its performance in a number of ways: (1) Dynamic replication of new instances of applications to several servers to raise throughput for scalability purposes, (2) Moving applications to servers to achieve load balancing or other resource management goals, (3) Caching entire applications on servers located closer to clients.National Science Foundation (9986397

    Semantic model-driven development of web service architectures.

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    Building service-based architectures has become a major area of interest since the advent of Web services. Modelling these architectures is a central activity. Model-driven development is a recent approach to developing software systems based on the idea of making models the central artefacts for design representation, analysis, and code generation. We propose an ontology-based engineering methodology for semantic model-driven composition and transformation of Web service architectures. Ontology technology as a logic-based knowledge representation and reasoning framework can provide answers to the needs of sharable and reusable semantic models and descriptions needed for service engineering. Based on modelling, composition and code generation techniques for service architectures, our approach provides a methodological framework for ontology-based semantic service architecture

    Two ways to Grid: the contribution of Open Grid Services Architecture (OGSA) mechanisms to service-centric and resource-centric lifecycles

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    Service Oriented Architectures (SOAs) support service lifecycle tasks, including Development, Deployment, Discovery and Use. We observe that there are two disparate ways to use Grid SOAs such as the Open Grid Services Architecture (OGSA) as exemplified in the Globus Toolkit (GT3/4). One is a traditional enterprise SOA use where end-user services are developed, deployed and resourced behind firewalls, for use by external consumers: a service-centric (or ‘first-order’) approach. The other supports end-user development, deployment, and resourcing of applications across organizations via the use of execution and resource management services: A Resource-centric (or ‘second-order’) approach. We analyze and compare the two approaches using a combination of empirical experiments and an architectural evaluation methodology (scenario, mechanism, and quality attributes) to reveal common and distinct strengths and weaknesses. The impact of potential improvements (which are likely to be manifested by GT4) is estimated, and opportunities for alternative architectures and technologies explored. We conclude by investigating if the two approaches can be converged or combined, and if they are compatible on shared resources
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