WSDL Documents

A WSDL document is just a simple XML document.

It contains set of definitions to define a web service.

The WSDL Document Structure

A WSDL document defines a web service using these major elements:

The main structure of a WSDL document looks like this:

<definitions>

<types>
   definition of types........
</types>

<message>
   definition of a message....
</message>

<portType>
   definition of a port.......
</portType>

<binding>
   definition of a binding....
</binding>

</definitions>

A WSDL document can also contain other elements, like extension elements and a service element that makes it possible to group together the definitions of several web services in one single WSDL document.

For a complete syntax overview go to the chapter WSDL Syntax.

WSDL Ports

The <portType> element is the most important WSDL element.

It defines a web service, the operations that can be performed, and the messages that are involved.

The <portType> element can be compared to a function library (or a module, or a class) in a traditional programming language.

WSDL Messages

The <message> element defines the data elements of an operation.

Each messages can consist of one or more parts. The parts can be compared to the parameters of a function call in a traditional programming language.

WSDL Types

The <types> element defines the data type that are used by the web service.

For maximum platform neutrality, WSDL uses XML Schema syntax to define data types.

WSDL Bindings

The <binding> element defines the message format and protocol details for each port.

WSDL Example

This is a simplified fraction of a WSDL document:

<message name="getTermRequest">
   <part name="term" type="xs:string"/>
</message>

<message name="getTermResponse">
   <part name="value" type="xs:string"/>
</message>

<portType name="glossaryTerms">
  <operation name="getTerm">
      <input message="getTermRequest"/>
      <output message="getTermResponse"/>
  </operation>
</portType>

In this example the portType element defines "glossaryTerms" as the name of a port, and "getTerm" as the name of an operation.

The "getTerm" operation has an input message called "getTermRequest" and an output message called "getTermResponse".

The message elements defines the parts of each message and the associated data types.

Compared to traditional programming, glossaryTerms is a function library, "getTerm" is a function with "getTermRequest" as the input parameter and getTermResponse as the return parameter.

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