A Quick Introduction to WSDL

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The Web Services Description Language (WSDL) is an XML message format for describing the network services offered by the server.

You use WSDL to create a file that identifies the services provided by the server and the set of operations within each service that the server supports.

For operation, the WSDL file also describes the format that the client must follow in requesting an operation.

The SOAP Toolkit for Windows Embedded CE is compliant with the Web Services Description Language (WSDL) 1.1 Specification, which can be found on the World Wide Web Consortium Web site.

Because the WSDL file sets up requirements for both server and client, this file is like a contract: The server agrees to provide certain services if the client sends a properly formatted SOAP request.

Suppose a WSDL file defines a service called StockQuoteService. This service describes operations such as GetLastTradePrice, GetLowestPriceOfTheDay, and GetHighestPriceOfTheDay. You place this file on the server.

A client who wants to send a SOAP request to the server first obtains a copy of this WSDL file from the server. The client then uses the information in this file to format a SOAP request.

The client sends this request to the server. The server executes the requested operation and sends the resulting stock price back to the client as a SOAP response.

Unless otherwise specified, the "wsdl" namespace is the namespace used for all WSDL elements discussed in this documentation.

The operations in the WSDL file can be document oriented or remote procedure call (RPC) oriented, as defined by the style attribute of the <soap:binding> element in the file.

If an operation in the WSDL file is document-oriented, the input (request) and output (response) messages specified for that operation contain XML documents.

For example, a WSDL file defines a SubmitPO operation such that this operation expects a purchase order document, which is an XML document, as the input message part and returns another XML document for the response that might have information such as the purchase order tracking number.

RPC-oriented operations have input messages that contain the operations' input parameters and output messages that contain the operations' results.

For example, the input message parts for the Add operation defined in the WSDL file in Code Listing for the Calc.wsdl File are the parameter values for the Add method on the server, while the output message part returns the result of the addition.

WSDL File Example

For an example of a WSDL file and a description of the file's contents, see About the Calc.wsdl File.