This paper brings forward a two-phase semantic service discovery mechanism which supports both the operation matchmaking and operation-composition matchmaking. A serial of experiments on a service management framework show that the mechanism gains better performance on both discovery recall rate and precision than a traditional matchmaker. Categories and Subject Descriptors D.2.12 [Software Engineering]: Interoperability ? data mapping, distributed objects, interface definition languages; H.3.5 [Information Storage and Retrieval]: Online Information Services ? data sharing, Web-based services General Terms: Algorithms, Design, Experimentation, Measurement, Performance