The current Web service technology brought a new potential to the Web of services. However, the success of Web services still depends on resolving three fundamental challenges, namely search, integration and mediation. In this paper we define an extended Web service stack enabling total or partial automation of web service provisioning process. With the goal of a maximal Web standards compliance, we describe various types of service semantics, use RDF Schema (RDFS) to define a pragmatic meaning for those descriptions, and use Semantic Annotations for WSDL and XML Schema (SAWSDL) to define a place for a semantic description in a Web service. We elaborate on the existing SAWSDL specifications and define precise rules for semantic annotations of Web services.