A correlation-based service mediator consists of Semantic Query Generator, Service Query Manager, Service Invocation Flow Generator, Service Invocation Manager, Expression Interpreter and Service Invocation Result Cache. The Semantic Query Generator converts service request to Semantic Query based on input/output parameters in the service request. The Service Query Manager interfaces with an Ontology Engine, passing query results to Service Invocation Flow Generator, which creates service invocation flow definition based on passed query results. The Service Invocation Manager executes flow definitions. It also manages a service invocation result cache, so that invocation results can be saved and reused for later service request. When the execution results are not available in cache, the Service Invocation Manager invokes service according to flow definition. When attribute dependent functions are invoked Expression Interpreter compute the execution results. The service mediator possesses two major functionalities: service matching and service invocation.