In a service-oriented architecture, adaptive and evolvable applications should be able to select, configure and compose different existing application services to deal with the changes which can arise from runtime contextual changes or the change of user requirements and preferences. To support this, hybrid service composition approaches have been proposed, in which the core of application logic, which is rather stable, is specified in terms of processes while rules are employed to specify the conditions and constraints to adapt the application behaviour. The rules are then exposed as a decision service which can be employed by the process to make adaptation decision with respect to runtime circumstances. The interaction between processes and decision services are generally performed in synchronous request-response manner. We argue that such an interaction is not efficient to support different types of adaptation at runtime and therefore asynchronous interaction should also be supported. In this paper, we present an adaptive service provisioning architecture and a decision service template allowing both synchronous request-response interaction and asynchronous notification. To motivate the proposed architecture and the decision service template, we use a blood pressure monitoring scenario from the homecare domain. We also explain the implementation of the proposed approach based on commercially available rule and process engines. Finally, we discuss: 1) what is the efficient way (synchronous request-response interaction vs. asynchronous notification) of calling decision service to execute different types of decision rules? and 2) to what extent the use of decision service facilitates dealing with the unforeseen changes?

Recent trends in the use of service oriented architecture for designing, developing, managing, and using distributed applications have resulted in an increasing number of independently developed and physically distributed services. These services can be discovered, selected and composed to develop new applications and to meet emerging user requirements. Service composition is generally defined on the basis of business processes in which the underlying composition logic is guided by specifying control and data flows through Web service interfaces. User demands as well as the services themselves may change over time, which leads to replacing or adjusting the composition logic of previously defined processes. Coping with change is still one of the fundamental problems in current process based composition approaches. In this paper, we exploit declarative and imperative design styles to achieve better flexibility in service composition.

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In this paper, we present a distributed Web service discovery architecture that is designed to be reliable, flexible and scalable. The architecture is based on the concept of distributed shared space and intelligent search among a subset of spaces. It allows the publishing of Web service descriptions as well as to submit requests to discover the Web service of user's interests. The Web service capabilities and the user requests (goal) are described using a Resource Description Framework (RDF) data model. The architecture supports integration of applications running on different resource specific devices. An application scenario is presented to illustrate the functionality of the proposed architecture.

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