Currently in the travel domain, most of the travel products are sold through global distribution aystems (GDSs). Since only major airline companies or hotel chains can afford to join GDSs, it is difficult for small and medium enterprises to market their travel products. In this chapter, we describe a middleware, called SATINE, to address this problem. In the SATINE middleware, existing travel applications are wrapped as Web services. Web services, as such, is of limited use because the service consumer must know all the details of the Web service like the functionality of the Web service (what it does) and the content and the structure of input and output messages. Therefore, we annotate both the service functionality and the service messages with Web ontology language (OWL) ontologies. Service functionality ontology is obtained from the “Open Travel Alliance (OTA)” specifications. Service message ontologies are automatically generated from the XML schema definitions of the messages. These local message ontologies are mapped into one or more global message ontologies through an ontology mapping tool developed, called OWLmt. The mapping definitions thus obtained are used to automatically map heterogeneous message instances used by the Web service provider and the consumer using a global ontology as a common denominator. This architecture is complemented by a peer-to-peer network which uses the introduced semantics for the discovery of Web services. Through the SATINE middleware, the travel parties can expose their existing applications as semantic Web services either to their Web site or to Web service registries they maintain. SATINE middleware facilitates the discovery and execution of these services seamlessly to the user.