Abstract: As the service-oriented computing technology matures, service composition has became a new model for business cooperation among enterprises in Internet era. WS-BPEL is the de-facto standard for service composition. However, because Web services arc loosely coupled, distributed, and autonomous, the reliability of BPEL processes can' t be assured when partner services fail. As a result, dynamic runtime substitution of partner services is needed. But BPEL provides only limited service substitution. And when the partner services arc stateful, the problem gets more complex.This paper presented an stateful aspect extension of WS-BPEL.Stateful aspects were used to store the conversational details of partner services. In case of partner service failures,the conversational details can be replayed on another ecquivalent partner service transparently for the BPEL process. Our approach makes WS-BPEL have some ability of self-healing and improves the reliability of processes.

Key words: Web service, WS-BPEL, Stateful aspect, Dynamic substitution