Web Services Description Language

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"WSDL" redirects here. For other uses, see WSDL (disambiguation).
Web Services Description Language
File name extension .wsdl
Internet media type application/wsdl+xml
Developed by World Wide Web Consortium
Contained by XML

The Web Services Description Language (WSDL, pronounced 'wiz-dəl' or spelled out, 'W-S-D-L') is an XML-based language that provides a model for describing Web services.

The current version of the specification is 2.0; version 1.1 has not been endorsed by the W3C but version 2.0 is a W3C recommendation. [1] WSDL 1.2 was renamed WSDL 2.0 because of its substantial differences from WSDL 1.1. By accepting binding to all the HTTP request methods (not only GET and POST as in version 1.1) WSDL 2.0 specification offers a better support for RESTful web services, much simpler to implement [2][3]. However support for this specification is still poor in software development kits for Web Services which often offer tools only for WSDL 1.1.

The WSDL defines services as collections of network endpoints, or ports. The WSDL specification provides an XML format for documents for this purpose. The abstract definition of ports and messages is separated from their concrete use or instance, allowing the reuse of these definitions. A port is defined by associating a network address with a reusable binding, and a collection of ports define a service. Messages are abstract descriptions of the data being exchanged, and port types are abstract collections of supported operations. The concrete protocol and data format specifications for a particular port type constitutes a reusable binding, where the operations and messages are then bound to a concrete network protocol and message format. In this way, WSDL describes the public interface to the web service.

WSDL is often used in combination with SOAP and XML Schema to provide web services over the Internet. A client program connecting to a web service can read the WSDL to determine what functions are available on the server. Any special datatypes used are embedded in the WSDL file in the form of XML Schema. The client can then use SOAP to actually call one of the functions listed in the WSDL.

XLang is an extension of the WSDL such that "an XLANG service description is a WSDL service description with an extension element that describes the behavior of the service as a part of a business process" [1].

Resources or services are exposed using WSDL by both Web Services Interoperability (WS-I Basic Profile) and WSRF framework.

Contents

[edit] Example WSDL file

Here is an example of a structured WSDL 2.0 document:

<?xml version="1.0" encoding="UTF-8"?>
<description xmlns="http://www.w3.org/ns/wsdl" 
             xmlns:tns="http://www.example.com/wsdl20sample" 
             xmlns:whttp="http://www.w3.org/ns/wsdl/http"
             xmlns:wsoap="http://www.w3.org/ns/wsdl/soap"
 
             targetNamespace="http://www.example.com/wsdl20sample">
 
 
<!-- Abstract types -->
   <types>
      <xs:schema xmlns="http://www.example.com/wsdl20sample"
                 xmlns:xs="http://www.w3.org/2001/XMLSchema" 
                 targetNamespace="http://www.example.com/wsdl20sample">
 
         <xs:element name="request">
            <xs:complexType>
               <xs:sequence>
                  <xs:element name="header" maxOccurs="unbounded">
                     <xs:complexType>
                        <xs:simpleContent>
                           <xs:extension base="xs:string">
                              <xs:attribute name="name" type="xs:string" use="required"/>
                           </xs:extension>
                        </xs:simpleContent>
                     </xs:complexType>
                  </xs:element>
                  <xs:element name="body" type="xs:anyType" minOccurs="0"/>
               </xs:sequence>
               <xs:attribute name="method" type="xs:string" use="required"/>
               <xs:attribute name="uri" type="xs:anyURI" use="required"/>
            </xs:complexType>
         </xs:element>
 
         <xs:element name="response">
            <xs:complexType>
               <xs:sequence>
                  <xs:element name="header" maxOccurs="unbounded">
                     <xs:complexType>
                        <xs:simpleContent>
                           <xs:extension base="xs:string">
                              <xs:attribute name="name" type="xs:string" use="required"/>
                           </xs:extension>
                        </xs:simpleContent>
                     </xs:complexType>
                  </xs:element>
                  <xs:element name="body" type="xs:anyType" minOccurs="0"/>
               </xs:sequence>
               <xs:attribute name="status-code" type="xs:anySimpleType" use="required"/>
               <xs:attribute name="response-phrase" use="required"/>
            </xs:complexType>
         </xs:element>
      </xs:schema>
   </types>
 
 
<!-- Abstract interfaces -->
   <interface name="RESTfulInterface">
      <fault name="ClientError" element="tns:response"/>
      <fault name="ServerError" element="tns:response"/>
      <fault name="Redirection" element="tns:response"/>
      <operation name="Get" pattern="http://www.w3.org/ns/wsdl/in-out">
         <input messageLabel="GetMsg" element="tns:request"/>
         <output messageLabel="SuccessfulMsg" element="tns:response"/>
      </operation>
      <operation name="Post" pattern="http://www.w3.org/ns/wsdl/in-out">
         <input messageLabel="PostMsg" element="tns:request"/>
         <output messageLabel="SuccessfulMsg" element="tns:response"/>
      </operation>
      <operation name="Put" pattern="http://www.w3.org/ns/wsdl/in-out">
         <input messageLabel="PutMsg" element="tns:request"/>
         <output messageLabel="SuccessfulMsg" element="tns:response"/>
      </operation>
      <operation name="Delete" pattern="http://www.w3.org/ns/wsdl/in-out">
         <input messageLabel="DeleteMsg" element="tns:request"/>
         <output messageLabel="SuccessfulMsg" element="tns:response"/>
      </operation>
   </interface>
 
 
 
<!-- Concrete Binding Over HTTP -->
   <binding name="RESTfulInterfaceHttpBinding" interface="tns:RESTfulInterface" 
            type="http://www.w3.org/ns/wsdl/http">
      <operation ref="tns:Get" whttp:method="GET"/>
      <operation ref="tns:Post" whttp:method="POST" 
                 whttp:inputSerialization="application/x-www-form-urlencoded"/>
      <operation ref="tns:Put" whttp:method="PUT" 
                 whttp:inputSerialization="application/x-www-form-urlencoded"/>
      <operation ref="tns:Delete" whttp:method="DELETE"/>
   </binding>
 
<!-- Concrete Binding with SOAP-->
   <binding name="RESTfulInterfaceSoapBinding" interface="tns:RESTfulInterface" 
            type="http://www.w3.org/ns/wsdl/soap" 
            wsoap:protocol="http://www.w3.org/2003/05/soap/bindings/HTTP/"
            wsoap:mepDefault="http://www.w3.org/2003/05/soap/mep/request-response">
      <operation ref="tns:Get" />
      <operation ref="tns:Post" />
      <operation ref="tns:Put" />
      <operation ref="tns:Delete" />
   </binding>
 
 
<!-- Web Service offering endpoints for both the bindings-->
   <service name="RESTfulService" interface="tns:RESTfulInterface">
      <endpoint name="RESTfulServiceRestEndpoint" 
                binding="tns:RESTfulInterfaceHttpBinding" 
                address="http://www.example.com/rest/"/>
      <endpoint name="RESTfulServiceSoapEndpoint" 
                binding="tns:RESTfulInterfaceSoapBinding" 
                address="http://www.example.com/soap/"/>
   </service>
</description>

[edit] WSDL Viewers

  • Liquid Xml
  • Improve WSDL viewer for Eclipse
  • WiSDale by xTend Inc.

[edit] References

  1. ^ Web Services Description Language (WSDL) Version 2.0 Part 1: Core Language.
  2. ^ Web Services Description Language (WSDL) Version 2.0 Part 2: Adjuncts.
  3. ^ WITW WSDL 2.0 HTTP Binding.

[edit] External links


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