Extending the Assurance Point (AP) Approach to Process Recovery for Use with Flow Groups

The concept of Assurance Points (APs) provides a new approach to addressing data consistency in processes composed of service invocations. APs allow for checking of user-defined correctness conditions at different points during the execution of a business process, along with options for recovery actions if those conditions are not met, where recovery actions include rollback, retry, and a recovery technique for hierarchically nested processes known as cascaded contingency. APs also serve as partial rollback points from which forward recovery can resume when an error occurs. This research has extended the AP concept to support parallelism within a process using the flow group construct. A flow group allows concurrent execution threads within a process, making the AP approach suitable for use in cloud computing environment. Assuming there are no data dependencies between the concurrent threads, this research has defined the placement and behavior of APs within flow groups, also defining the recovery semantics for rollback, retry, and cascaded contingency when failure occurs within a flow group. These extensions have been designed with the intent of minimizing rollback and unnecessary backwards recovery activities for concurrent execution threads. This paper formalizes the use of APs and recovery actions within a flow group by Petri Nets.