The Design And Implement Of A Metadata-driven Web Service QoS Enforcement Framework

The Web service platform is gaining popularity as an highly mature approach of intergrating applications in diverse and heterogeneous distributed environments.One of the biggest barriers preventing widespread adoption of this technology in enterprise misson- critical applications is a lack of products that support non-functional features of web service,such as security,transactionality and reliability.The approach of using metadata-driven QoS enforcement through dynamic discovery and binding is a popular solution which comply with the features of web service.This solution needs a language describing QoS of web service and enforcements in concrete executing environment and mapping layer.Though detailed comparison and consideration on security and reliable messaging,the language to describe QoS requirement of a service in WS-Policy specification is extended to enhance the ablility of expressing security requirements.QoS requirements of web services are expressed as policies.A mathematical model is abstract from this language through the abstraction from policy operator to logic operator.This model make the language more machine-readable and thus greatly simplify the management and manipulation of the policy document.A medatada-driven web service QoS enforcement framework is designed and implemented based on the policy language and the Axis2 open source project.It provide web service invocations with secure and reliable messaging enforcement.It can interoperate with web services in other popular SOA platforms and can easily extended to provide support for other domain-specific quality requirements.Through specifying control SOAP message,the system completely support complex interoperation model of mutiple policy negotiation.