Schema Files and Service Definition Documents

The Liberty Alliance Project has created a number of XML Schema Definition (XSD) files and Web Services Description Language (WSDL) documents to complement the specifications. XSD files specify the information that the corresponding service can host by defining the data and data structure. Typically, this structure is hierarchical and has one root node. Individual branches of the structure can be accessed separately, and the whole structure can be accessed by pointing to the root node. The data might be stored in implementation-specific ways. However, the data will be exposed by the service using the XML schema and the WSDL definition of the service type.

The purpose of an XML schema is to describe the structure of an XML document. The XML schema file format is XSD. XSD is an XML-based alternative to the Document Type Definition (DTD) format. A DTD also describes the structure of an XML document, but it is not in the XML format.

The WSDL definition is XML-based and describes how to communicate with the web service; namely, protocol bindings and message formats. In simpler terms, the WSDL for a specific service describes the public interface for that web service. The available XSD files and WSDL documents specific to the previously described specifications can be found on the Liberty Alliance Project web site.