Building a valid web service composition using integrated service substitution and adaptation

Traditional web service composition is often statically generated using knowledge available at the design time. In addition, they assume the final composition workflows are always executable. However, this assumption might be false since the environment can change during the execution time. Therefore, it is essential that the correctness of a partial/full composition needs to be validated and maintained during its execution. This paper utilises the notion of workflow exception handling to generate valid web service compositions. More specifically, we propose the concepts of synchronous exception handling and asynchronous service interrupt (ASI). The synchronous workflow exception is used in the initial service configuration which contains static service substitution, planning time-service adaptation and mapping time-service adaptation, while the ASI is implemented via dynamic service substitution and binding time-service adaptation. The integrated usage of the above approaches is demonstrated by an implementation of an e-hospital application.