Web Services protocols (WSDL, UDDI) concepts

Web Services protocols (WSDL, UDDI) concepts

Web Services Description Language (WSDL) is an XML-based standard specification for describing Web services. WSDL defines an XML format for describing network services as a set of endpoints that operate on messages that contain either document-oriented or procedure-oriented information.

The WSDL service description can be structured in many ways. However, to assist with publishing and finding WSDL service descriptions in a UDDI registry, WSDL documents consist of two main parts:

The service interface definition describes the abstract type interface and its protocol binding, known as the WSDL binding document
The service implementation definition describes the service access location information, known as the WSDL service document
When creating Web services with the Apache Axis run-time environment, the Web services tools create a single WSDL document when generating Web services from Java™ beans or EJBs. This WSDL document contains both the service interface and implementation documents.

A service interface is described by a WSDL document that contains the types, import, message, portType, and binding elements. A service interface contains the WSDL service definition that will be used to implement one or more services. It is an abstract definition of a Web service, and is used to describe a specific type of service. This document can reference another service interface document using an import element. The Web services tools in this product generate a service interface document that contains only the message and portType elements that are referenced by the binding document that contains only bindings for the portType.

The service implementation document contains the service elements. A service implementation document contains a description of a service that implements a service interface. At least one of the import elements will contain a reference to the WSDL service interface document; however monolithic WSDL such as that created using the Axis run-time environment does not have imports.