The Web services technology is founded on the use of a number of standards based particularly on XML, such as SOAP, WSDL, UDDI and BPEL. However, these standards are not sufficient to allow an automation of the various tasks of the Web service's life cycle, namely the discovery, the invocation, the publication and the composition. Recently, the W3C consortium produced the SAWSDL language. This language is a new standard enabling the semantic Web services' description. It allows the semantic annotation of WSDL elements and XML schemas. Within the framework of the MDA approach, this paper proposes a semantic Web services metamodel founded on SAWSDL language. This metamodel would constitute an abstraction of the complexity of the use of the WSDL standard. It would also enable developers to easily implement semantic Web services based applications.