Concurrency control in Web service orchestration

Although the issue of atomicity in Web service orchestration is well understood and widely studied, the role of concurrency control is not neither well understood nor studied in this context. In this paper, we restrict ourselves on this issue. First we characterize the features of isolation requirements of the business processes that are processed by orchestrating Web services. Such features are also motivated by giving a motivating example. Then, we present our developed concurrency control model by considering the specification of work-flowspsila isolation requirements as well as the scheduler that enforces the isolation specifications. The key idea is to specify isolation requirements as consistency constraints in SQL database language. Workflow instances then set and unset constraints in a way similar to the way in which traditional transactions obtain and release locks. A gain of this approach is that the constraints nicely match the workflow isolation requirements, which in turn makes it possible to achieve a high degree of concurrency. In addition, the management of the constraints can be easily implemented by utilizing the services of the underlying SQL-system.