Abstract. The SOAP Service Description Language (SSDL) is a SOAPcentric language for describing Web Service contracts. SSDL focuses on message abstraction as the building block for creating service-oriented applications and provides an extensible range of protocol frameworks that can be used to describe and formally model component composition based on Web Service interactions. Given its novel approach, implementing support for SSDL contracts presents interesting challenges to middleware developers. At one end of the spectrum, programming abstractions that support message-oriented designs need to be created. At the other end, new functionality and semantics must be added to existing SOAP engines. In this paper we explain how component developers can create message-oriented Web Service interfaces with contemporary tool support (specifically the Windows Communication Foundation) using SSDL. We show how SSDL can be used as an alternative and powerful metadata language natively alongside existing tooling without imposing additional burdens on application developers. Moreover, we describe the design and architecture of the Soya middleware which supports SSDLbased development of Web Services on the WCF platform.