This paper presents the work that has been done at Thales Communications France regarding the specification and implementation of a semantic Web Service discovery and orchestration platform as part of the S4ALL ITEA program [13]. The central objective is to increase systems' interoperability and adaptability by adding semantic annotations on service declarations and business processes, in order to capitalize on the information contained in ontologies. The semantic platform was developed using common (semantic) web languages and technologies like the Semantic Annotation for WSDL Language (SAWSDL), BPEL, OWL and the UDDI service registry. The following twofold approach has been undertaken: firstly, specifying a SAWSDL to UDDI structural mapping. Its implementation allows us to publish semantically annotated declarations into a well-known service registry and make discovery queries regarding semantic concepts extracted from ontologies. Secondly, implementing a semantically aware business process execution engine able to conduct reasoning on processes where service requirements are expressed using ontological concepts. It also supports a basic form of data adaptation.