The detection of suitable services for solving a defined task, commonly referred to as Web service discovery, is regarded as the most important operation in service-oriented environments, since it is the prerequisite of the core technical benefit of SOA: reuse. With the current Web service technology stack, service discovery is limited to a syntactic keyword based search mechanism aided by a simple metadata service description taxonomy and browsing capabilities. In future service environments with already thousands of available services in local organizational infrastructures, much more sophisticated discovery techniques are required. The emerging concept of Semantic Web services (SWS) promises to address the deficiencies of today's Web service technologies. The research on Semantic Web services concentrates on the development of inference based approaches to enhance the discovery, composition and execution of Web services towards a full-blown automated process.