The W3C Web Services Activity. has posted the candidate recommendation of Semantic Annotations for WSDL. According to the draft,
Semantic Annotations for WSDL and XML Schema (SAWSDL) defines how to add semantic annotations to various parts of a WSDL document such as input and output message structures, interfaces and operations. The extension attributes defined in this specification fit within the WSDL 2.0 extensibility framework. For example, it defines a way to annotate WSDL interfaces and operations with categorization information that can be used to publish a Web service in a registry. The annotations on schema types can be used during Web service discovery and composition. In addition, SAWSDL defines an annotation mechanism for specifying the structural mapping of XML Schema types to and from an ontology such mappings could be used during invocation, particularly when mediation is required. To accomplish semantic annotation, SAWSDL defines extension attributes that can be applied both to WSDL elements and to XML Schema elements.
Semantic annotations are references from an element within a WSDL or XML Schema document to a concept in an ontology or to a mapping. This specification defines annotation mechanisms for relating the constituent structures of WSDL input and output messages to concepts defined in an outside ontology. Similarly, it defines how to annotate WSDL operations and interfaces. Further, it defines an annotation mechanism for specifying the structural mapping of XML Schema types to and from an ontology by means of a reference to a mapping definition. The annotation mechanism is independent of the ontology expression language and this specification requires no particular ontology language. It is also independent of mapping languages and does not restrict the possible choices of such languages.
