The DeltaGrid Service Composition and Recovery Model

This research has defined an abstract execution model for establishing user-defined correctness and recovery in a service composition environment. The service composition model defines a flexible, hierarchical service composition structure, where a service is composed of atomic and/or composite groups. The model provides multi-level protection against service execution failure by using compensation and contingency at different composition granularity levels, thus maximizing the potential for forward recovery of a process when failure occurs. The recovery procedures also include rollback as a recovery option, where incremental data changes known as deltas are extracted from service executions and externalized by streaming data changes to a Process History Capture System. Deltas can then be used to backward recover an operation through a process known as Delta-Enabled Rollback. This article defines the semantics of the service composition model and the manner in which compensation, contingency, and Delta-Enabled-rollback are used together to recover process execution. The authors also present a case study and describe a simulation and evaluation framework for demonstrating the functionality of the recovery algorithm and for evaluating the performance of the recovery command generation process.