Describe Your Web Service with WSDL
For clients to be able to call a Web service they need to know the available method names, the parameter names and types, and the expected output type for each method. Therefore, you need to generate some kind of interface that can sit between the server and client so each can understand the other's request or response. The Web Services Description Language (WSDL) fulfills these interface requirements.

WSDL, officially, is an XML grammar that contains information about the interface and semantics of a call to a Web service. But you can think of a WSDL file as an XML document that describes a set of SOAP messages, and how those messages are exchanged. In other words, WSDL is to SOAP as Interface Definition Language (IDL) is to CORBA or COM. Because WSDL is also XML, it is humanly readable and editable.

After developing a Web service, you publish its description and a link to it in a UDDI (Universal Description, Discovery and Integration) repository so that potential users can find it. When someone thinks they want to use your service, they request your WSDL file to find out the details for using the service. They then use the information in your WSDL file to form a SOAP request message.

The WSDL file is the heart of the Web service transaction, because without it the clients can't communicate with your Web service. To understand the value of WSDL, imagine you want to start calling a SOAP method provided by one of your business partners. You could ask him for some sample SOAP messages and write your application to produce and consume messages that look like the samples, but that can be error-prone. For example, you might see a customer ID of 8907 and assume it's an integer when in fact it's a string. The WSDL file specifies the contents of request and response messages unambiguously.


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Karpagarajan. R
Necessity is the mother of invention