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Facing changing environments and evolving business rules, composite services ought to be adaptable, even at run-time. Existing mainstream service composition languages and execution engines exhibit insufficient support for variability and adaptability to cater for dynamic changes. Research efforts have been put on the extension of the languages and argumentation of the engines. However, how to ensure the correctness for the adaptation of a running composite service instance and minimize unnecessary re-execution of component services remains a challenge. To address this problem, we propose a model-based approach that allows run-time adaptation of composite services. It is based on an instance transfer mechanism that transfers an active instance of the old service composition schema to a appropriate state of the new schema. Algorithms are proposed to find the appropriate destination states of the transformation. After the migration, the suspended instances can resume their execution according to the new schema. An example based on a FindRoute composite service is also included.
Date of Conference: 23-26 Sept. 2008