Migration Validity of WS-BPEL Instances Revisited

WS-BPEL processes ought to be adaptable even at run-time so as to adapt to the changing environments and requirements. It is cost-ineffective and time-consuming to restart a running WS-BPEL instance from scratch after the WS-BPEL process is changed. Instead, a WS-BPEL instance had better be transferred to the updated process. Current approaches to validity checking of instance migration are too conservative and thus few instance migrations are considered to be valid. To address this problem, we propose a novel criterion for valid migration which is based on the dynamic dependence graph for the trace of a WS-BPEL instance. Compared with existing approaches, our approach is significantly less conservative, that is, it allows more instances to migrate to the updated process. We illustrate the applicability and effectiveness of our approach by dynamically updating the WS-BPEL process of a travel agency.