Semantic Annotations for WSDL and XML Schema — Usage Guide

Web services provide a standards-based foundation for exchanging information between distributed software systems. The World-Wide Web Consortium (W3C) standard Web Services Description Language (WSDL) specifies a standard way to describe the interfaces of a Web Service at a syntactic level and how to invoke it. While the syntactic descriptions provide information about the structure of input and output messages of an interface and how to invoke them, semantics are needed to describe what a Web service actual does. These semantics when expressed in formal languages disambiguate the description of Web services interfaces paving the way for automatic discovery, composition and integration of software components. WSDL does not explicitly provide mechanisms to specify the semantics of a Web service. Semantic Annotations for WSDL (SAWSDL) is an effort to define mechanisms by which semantic annotations can be added to WSDL components. Many of the concepts in SAWSDL are based on an earlier effort WSDL-S, a W3C submission. This usage guide is an accompanying document to SAWSDL specification. It presents examples to illustrate how to associate semantic annotations with a Web service that could be used for classifying, discovering, matching, composing, and invoking Web services. Some of the examples illustrated in this document use RDF and OWL Web Ontology Language for representing ontologies. Some knowledge of RDF and OWL is useful for understanding this document, but not essential.