Technology Of Web Services Monitor And Substitution For The Software Dependability

SOA (service-oriented architecture) was first put forward by Gartner in 1996 and has become the hotspot both in academia and in industry recently. It's believed that SOA is promising to become the main paradigm of enterprise software architecture in the future. In the face of more and more complicated and changeable software requirements, SOA provides a rapid and effective solution for services reusability and cross-platform business integration and interoperability with its characteristics of opening, loosely-coupling and platform-independence. As the most popular scheme of SOA, Web Services based on its opening architecture and standard specifications are rapidly accepted by industry and are regarded as the main distributed computing model in the future. Web Services utilize the mature internet protocols and define the platform-independent message model and formal service description to guarantee the loose-coupling invoking way between service consumers and providers. However, the distribution characteristic presents new challenges to the management of web services.The current web services architecture, which merely describes the static information about web services and lacks the dynamic information, is not powerful enough to guarantee the dependability and efficiency in the process of web service invoking in the ever-changing Internet environment. In fact, some web services have the similar function and interface, that's, they could be substituted by one another. According to this precondition, we modify the current architecture and propose a novel model which is called Representative-Replication model to improve the dependability of web services in the process of invoking.In Representative-Replication model, representative is a special web service, which abstracts a set of substitutable web services and never provides any business function to the public. It is only responsible for dynamically selecting the most appropriate web service according to the QoS evaluation in the process of invoking and updating the value of QoS according to the result of invoking. When the invoking fails, representative will bind to another web service to guarantee the success of the invoking. Besides, the new model ensures the dependability of the representative with the technique of replication, which prevents the overhead of the representative. An effective synchronized algorithm has also been designed to guarantee the sharing of the web services with high quality.Finally, the simulated experiments suggest the feasibility and efficiency of the model in the enhancement of dependability of web services, which is at the cost of little extra time when compared with the original Web services architecture.