Planning Process Instances with Web Services

Planning is an important approach to developing complex applications composed of web services, based upon semantic annotations of these services. Despite numerous publications in recent years, the problems considered in the literature typically do not require planning as it has been well-defined in computer science. This could lead to confusion about which technologies are being designated, and raises the question of what whether planning is an appropriate technology for services. We describe the essential features of planning technology and note its advantages, which include the dynamic synthesis of processes and the lack of need to verify the correctness of the message exchange. We show that planning technology really is necessary by giving an example of web service composition that cannot be solved with simpler technologies as could previously published examples. We describe the basics of adapting planning to web service composition. We restrict its use to process instance synthesis in order to simplify exploration of some fundamental issues. A major issue is that web services are usually incompletely modeled. We illustrate this with a second example. We show some additional semantic annotations of web services can be used to solve the problems similar to the example when used in conjunction with re-planning.