Querying Mediated Web Services

Web services provide interfaces to web resources described by WSDL interface definitions. The Web Service MEDiator system (WSMED) enables querying data accessible through web services. WSMED allows web service meta-data to be automatically extracted from any WSDL description. Then views can be created in terms of the imported meta-data and queried using SQL. To enhance query performance, WSMED permits to complement the automatically extracted web service meta-data with semantic enrichments. A WSMED prototype is being evaluated over existing web services to verify the effectiveness of the approach. It is being investigated how semantic enrichments and other query optimization methods are useful for efficient querying of mediated web services. invokes the web service operations to retrieve the desired information. In this work we provide the capability to define declarative queries and views over data extracted from web services. The WSMED (Web Service MEDiator) engine permits integration of data from heterogeneous remote systems accessible through web services. It permits SQL queries over data produced by distributed web service enabled data sources. Any web service can be accessed by importing its WSDL interface descriptions. The imported WSDL interface descriptions are stored in WSMED as meta-data. To enhance query processing, the meta-data can be complemented with user-provided semantic enrichments describing properties of data in the sources not provided by WSDL. The user can define views of data from the web services in terms of the imported meta-data. Applications then query these views transparently as if all the data was stored in a relational database. SQL is used by applications and users for querying these views. Composed SQL views can be defined in terms of the web service views. A mediator query optimizer automatically decides strategies to access wrapped web service operations to minimize the execution cost.