WSDL - Xml format

WSDL, aka Web Services Description Language, is a xml format created in 2000.

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24Years Old

The Web Services Description Language (WSDL ) is an XML-based interface definition language that is used for describing the functionality offered by a web service. The acronym is also used for any specific WSDL description of a web service (also referred to as a WSDL file), which provides a machine-readable description of how the service can be called, what parameters it expects, and what data structures it returns. Therefore, its purpose is roughly similar to that of a method signature in a programming language. Read more on Wikipedia...

WSDL Wikipedia page
WSDL docs
See also: (3 related languages)XML, SOAP, BPEL

Example from Wikipedia:

<?xml version="1.0" encoding="UTF-8"?>
<description xmlns="http://www.w3.org/ns/wsdl" 
             xmlns:tns="http://www.tmsws.com/wsdl20sample" 
             xmlns:whttp="http://schemas.xmlsoap.org/wsdl/http/"
             xmlns:wsoap="http://schemas.xmlsoap.org/wsdl/soap/"
             targetNamespace="http://www.tmsws.com/wsdl20sample">

<documentation>
    This is a sample WSDL 2.0 document. 
</documentation>

<!-- Abstract type -->
   <types>
      <xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"
                xmlns="http://www.tmsws.com/wsdl20sample"
                targetNamespace="http://www.example.com/wsdl20sample">
                 
         <xs:element name="request"> ... </xs:element>
         <xs:element name="response"> ... </xs:element>
      </xs:schema>
   </types>

<!-- Abstract interfaces -->
   <interface name="Interface1">
      <fault name="Error1" element="tns:response"/>
      <operation name="Get" pattern="http://www.w3.org/ns/wsdl/in-out">
         <input messageLabel="In" element="tns:request"/>
         <output messageLabel="Out" element="tns:response"/>
      </operation>
   </interface>

<!-- Concrete Binding Over HTTP -->
   <binding name="HttpBinding" interface="tns:Interface1" 
            type="http://www.w3.org/ns/wsdl/http">
      <operation ref="tns:Get" whttp:method="GET"/>
   </binding>
   
<!-- Concrete Binding with SOAP-->
   <binding name="SoapBinding" interface="tns:Interface1" 
            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" />
   </binding>

<!-- Web Service offering endpoints for both bindings-->
   <service name="Service1" interface="tns:Interface1">
      <endpoint name="HttpEndpoint" 
                binding="tns:HttpBinding" 
                address="http://www.example.com/rest/"/>
      <endpoint name="SoapEndpoint" 
                binding="tns:SoapBinding" 
                address="http://www.example.com/soap/"/>
   </service>
</description>