Research On Web Service Composition Technologies

With the evolution of service-oriented architecture, providing support for compositing distributed and autonomous web services into business applications has become a key area in the software engineering research. Agility of business applications will be obtained through utilizing web services composition technologies. However, at this stage, the research on these emerging technologies does not solve the necessary problems to build web service compositions, especially in web service composition modeling, composition verification, executable semantics and supporting systems.In this thesis, we investigated several key issues of web service composition. Firstly, WSCG (Web Service Composition Graph) model, a model for web service composition, is proposed, which consists of visual presentation model and executable model. According to this model, the interactions and execution sequences among web services are characterized by WSCG nodes and edges and their attributes. Based on attributed graph theory, we give the formal definition of WSCG model. Secondly, based on attributed graph grammar theory, we present a meta-model named WSCG grammar for WSCG model. Elements, elements' attributes and elements' relationships of WSCG model are all defined in WSCG grammar. Directed by WSCG grammar, a WSCG model can be developed, which can satisfy the specification of WSCG model and eliminate some structure errors.To ensure the well-formed of WSCG model, we have developed an algorithm to check the type-safety of WSCG model, in which data edges of WSCG model can be used to check whether the export messages of an edge's source node is matched with the import messages of the edge's target node, and to determine whether the import messages of a node is self-contained. We also develop another algorithm, which is based on WSCG dependence graph that simulates the WSCG dynamic behaviors, to eliminate the deadlock of WSCG model.Using attributed graph transformation productions defined on WSCG model, the consistency between WSCG execution instance and WSCG model is guaranteed with a sound formal semantic basis. The executable semantics of WSCG model can be classified into two types, the one type is defined on WSCG meta-model, and the other type is domain-oriented, whose executable semantics are customized by extending theevent handle in executable model. To improve the execution performance of WCSG model, all transformation productions, which express executable semantics of WSCG model, have been divided into several parallel independent disjoint set, and sequential independent sets for every transformation productions are also defined.Lastly, to support, facilitate and assist the visual design, verification and execution of web service composition, we present WSCG framework that includes web service composition model design, WSCG model, WSCG transformation and WSCG verification. At the same time, WSCG toolset and WSCG runtime, prototype systems for proposed framework, are implemented in J2EE environment. We outline the architecture of both prototypes and detail the design and implementation of components of prototypes, such as: WSCG editor, WSCG coordinator, state manager, web service broker and WSCG peer service.