Process Mediation, Execution Monitoring and Recovery for Semantic Web Services.
Katia P. Sycara, Roman Vaculín · 2008
One of the main promises of web services standards is to enable and facilitate seamless interoperability of diverse applications and business processes implemented as components or services. A service can be part of a business workflow that prescribes control and data flows of complex applications. As business needs change, processes may need to get reconfigured or additional process components and services may need to be added. As a result of these changes, the previous components must become interoperable with the new one. This can be accomplished by making manual changes to the existing workflow components and programming the new components in such a way as to have interoperability built-in. This is a rather laborious and inefficient process since it must be repeated every time workflow reconfiguration is needed. Also, since many different elements of a business workflow may be under the control of third parties (e.g. subcontractors), additional costly coordination will be needed with these third parties to manually find interoperability solutions. Moreover, since the Internet gives the opportunity to dynamically discover service providers, it is often not a priori known which service provider may best fit the application workflow changing needs. In other words, the new service component that must interoperate with old ones, is dynamically discovered. Therefore, (a) a more general solution is desired, namely the ability to achieve process interoperability (e.g. interoperability of existing processes with new ones) without actually modifying their implementation and interfaces, and (b) the mediation may need to be done dynamically even at runtime, which implies that only minimal assumptions about knowledge of service requester and service provider interfaces is allowed. One solution to this requirement is to apply a process mediation component which resolves all incompatibilities and generates appropriate mappings between different processes while making minimal assumptions about implementation details of service providers and requesters. Creating such a process mediation component is a very challenging task. Service providers and requesters may not share basic standards for Web Service specification; they may not share domain ontologies; furthermore, they typically do not do share the same data models or interaction protocols. Moreover, the changing business needs may dictate that existing services are modified, thus rendering previous compatible interactions incompatible. As a result, a mediation module must deal with incompatibilities of multiple types and also be able to incorporate adaptive reasoning mechanisms to address dynamic environment changes. Current web services standards provide a good basis for achieving at least some level of interoperability. WSDL allows to declaratively describe operations and format of messages and data structures that are used to