Workflow reconfiguration traditionally modifies only workflow definitions. Incorporating dynamism in web service workflows should also adapt instance execution as services change availability. Commercial workflow engines lack mechanisms to adapt instances except where instances deploy with all possible workflow paths, to achieve pseudodynamism. This error prone method has the potential for unsound specifications and still does not allow runtime modifications. We perform workflow reconfiguration through an inspection-feedback loop that decouples services specifications and priorities that can change BPEL workflows from their actual execution. When a change occurs, such as service unavailability, immediate adaptation of the workflow instance takes place. To guarantee proper reconfiguration, we formally specify the architecture, interactions, and change directives, according to a natural separation of reconfiguration concerns. We prove the workflow instance will correctly adapt to an alternative service when certain conditions are met.
Workflow languages can compose and sequenceWeb service invocations to achieve meaningful task results. Updating workflows when services and task goals change is difficult, and automating the change at runtime requires workflow goals and service preferences to be stated, organized, and controlled. Changing the preferences should be immediately reflected in executing workflows. While there are many applications that could benefit from this dynamic reconfiguration, managing such preferences can be daunting. We introduce NeWT, a Next-generation Workflow Toolkit that combines workflow editing with utilities for introducing and managing change. NeWT allows the novel input of goal preferences to use workflows that accomplish the same task but in different ways to be interchangeable according to the current goal. It accepts that multiple, competing Web services will be available and should be interchanged as dictated by need. We detail the implementation of these concepts using a crisis management example.
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