Dynamically Changing Workflows of Web Services

Abstract

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 pseudo-dynamism. 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.