A general model for nested transactional workflows

This paper applies concepts from transaction processing to workflows, thus enabling workflows to exhibit relaxed transactional behaviour. A general model for transactional workflows is presented. We define correctness of transactional workflows in terms of the model, and use the model to find schedules such that the execution of a transactional workflow is guaranteed to terminate in one of its acceptable termination (commit or abort) states. We allow a transactional workflow to consist of a number of tasks composed by the constructs ordering, contingency, alternative, conditional and iteration. In addition, we show how the model can be used to support proper nesting of transactional workflows to reduce the diffculty of scheduling algorithms and to provide for structured and modular TWF specification.