213 research outputs found

    An Architecture for Flexible Web Service QoS Negotiation

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    The web service selection phase is usually driven only by functional requirements. Non functional requirements, such as quality of service, should be negotiated by the service consumer and the service provider during service invocation in order to produce a contract to manage service provisioning and to monitor the actual fulfilment of negotiated SLAs. In this paper an automated approach to web service QoS negotiation is proposed; the negotiation is performed by a Negotiation Broker to which both the consumer and the service provider can notify their preferences on QoS attributes and negotiation strategies by specifying the value of a relatively small set of parameters. When consumers are unable to specify such parameters or do not trust the service provisioning platform, negotiation can also be automated only on the provider side, allowing the direct interaction of the service consumer with the broker. An architecture to support the above mentioned functionalities is also described

    A framework for QoS-based Web service contracting

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    The extensive adoption of Web service-based applications in dynamic business scenarios, such as on-demand computing or highly reconfigurable virtual enterprises, advocates for methods and tools for the management of Web service nonfunctional aspects, such as Quality of Service (QoS). Concerning contracts on Web service QoS, the literature has mostly focused on the contract definition and on mechanisms for contract enactment, such as the monitoring of the satisfaction of negotiated QoS guarantees. In this context, this article proposes a framework for the automation of the Web service contract specification and establishment. An extensible model for defining both domaindependent and domain-independentWeb service QoS dimensions and a method for the automation of the contract establishment phase are proposed. We describe a matchmaking algorithm for the ranking of functionally equivalent services, which orders services on the basis of their ability to fulfill the service requestor requirements, while maintaining the price below a specified budget.We also provide an algorithm for the configuration of the negotiable part of the QoS Service-Level Agreement (SLA), which is used to configure the agreement with the top-ranked service identified in the matchmaking phase. Experimental results show that, in a utility theory perspective, the contract establishment phase leads to efficient outcomes. We envision two advanced application scenarios for the Web service contracting framework proposed in this article. First, it can be used to enhance Web services self-healing properties in reaction to QoS-related service failures; second, it can be exploited in process optimization for the online reconfiguration of candidateWeb services QoS SLAs

    On Automated Generation of Web Service Level Agreements

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    Before a service invocation takes place, an agreement between the service provider and the service user might be required. Such an agreement is the result of a negotiation process between the two parties and defines how the service invocation has to occur. Considering the Service Oriented Computing paradigm, the relationship among providers and users is extremely loose. Traditional agreements are likely to concern long term relationships and to be manually performed. In this paper, we propose a model to generate service level agreement on-the-fly. Just before the invocation commences, the quality of the service is negotiated in order to generate a service level agreement tied to that specific invocation. Such an approach relies on a quality model that supports both users requirements and providers capabilities definition
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