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The rapid development of web service technology brings up a number of crucial requirements for designing service computing runtime, such as supporting multiple message exchange patterns, switching among different transports, integrating various extended web service protocols and achieving robust performance under high concurrency. Based on staged event-driven architecture, we propose a novel architecture for an adaptive web-service-centric service computing runtime, named SEDA4SC. In SEDA4SC, the process of basic and extended web service protocols is divided into four primary event-driven stages to enable system independence and module isolation. Moreover, this architecture allows messages to be handled in two independent pipelines: the input pipeline and the output pipeline. Arbitrary message exchange patterns can be supported through a combination of the two pipelines. With SEDA4SC, we design and implement a service computing runtime system. The performance evaluation results show that our system exhibits robust performance under high concurrency.

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It is very difficult to construct a correct BPEL engine, which is the runtime environment supporting the execution of BPEL processes. The main reason is the complexity of informal specification. It leads to that the programmers build the system without knowing precisely what they do. In this paper, we provide an operational semantics of BPEL based on Abstract BPEL Machine (ABM). ABM is a formal model that simulates the execution environment of BPEL. The functional behavior of a BPEL engine can be described as the input-output state transitions on ABM. It can be further divided into the execution behavior of each BPEL constructs, such as activities and handlers. The aim of our work is to provide the precise understanding on execution model of BPEL, and narrow the gap between BPEL specification and BPEL implementation. The result can be used as a formal specification to construct a correct BPEL engine.