Building Adaptive Services for Distributed Systems

There exists a growing class of distributed applications that require adaptive middleware services, i.e., services that are able to monitor changes in the execution environment, and in the user requirements, reacting to these changes by adapting their behaviour. This paper presents a framework that supports the definition, implementation, and execution of reconfigurable service compositions, and puts forward an approach to the construction of adaptive distributed applications. Adaptiveness is achieved through the dynamic reconfiguration of service compositions in accordance with high-level policies. The framework allows those reconfigurations to be carried out transparently to the application. This approach is illustrated using a messaging application.