This paper presents a meta-model for describing preferences of Web services. Two types of preferences are examined namely privacy and membership. Privacy restricts the data that Web services exchange, and membership restricts the peers that Web services interact with. Both types have risen lately with force in response to the open and dynamic nature of the Internet. While most of the research work on Web services has been driven by the concerns of users, this paper stresses out the concerns of providers of Web services. Different meta-classes like Web service, functionality, and WSDL are included the meta-model for Web services' preferences. To guarantee the satisfaction of these preferences, policies are developed in this paper.