WSDL Document

A WSDL document is just a simple XML document. It contains a series of definitions that describe a web service.

WSDL Document Structure

A WSDL document uses these main elements to describe a web service:

The main structure of a WSDL document looks like this:

WSDL Document Example

<definitions>

<types>
  data type definitions........
</types>

<message>
  definition of the data being communicated....
</message>

<portType>
  set of operations......
</portType>

<binding>
  protocol and data format specification....
</binding>

</definitions>

A WSDL document can contain other elements, such as extension elements, and a service element, which can group definitions of several web services into a single WSDL document.

WSDL Port

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

It describes a web service, the operations that can be performed, and the related messages.

You can compare the <portType> element to a function library (or a module, or a class) in traditional programming languages.

WSDL Messages

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

Each message consists of one or more parts. These parts can be compared to the parameters of a function call in traditional programming languages.

WSDL Types

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

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

WSDL Bindings

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

WSDL Example

Here is a simplified snippet 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 named "getTermRequest" and an output message named "getTermResponse".

The <message> element defines the parts of each message and their associated data types.

By analogy with traditional programming, glossaryTerms is a function library, and "getTerm" is a function with an input parameter "getTermRequest" and a return parameter "getTermResponse".