Continuous Orchestration of Web Services via Planning

The service-oriented paradigm is rapidly emerging as the key approach to develop distributed business applications. Its enactment requires the ability to automatically coordinate existing services to realize novel and powerful desired functionalities, and planning-based solutions have proved to be strong candidates for this hard task. However, no current approach can satisfactorily coordinate stateful services that evolve continuously and indefinitely in an asynchronous way, such as e.g. notification services made increasingly available by business entities. This severely limits the practical applicability of current solutions. In this paper, we provide for the first time a full-fledged planning-based solution to the problem of continuously orchestrating stateful asynchronous services. To do so, we adopt a simple yet expressive requirement language, and we devise a novel planning algorithm that solves preference-ordered maintenability goals in the presence of exogenous events. Our approach is correct and complete, and our tests on a symbolic BDD-based implementation witness its ability and effectiveness in dealing with significant and realistic scenarios which no other current approach can tackle.