Web Services WSDL

WSDL is an XML-based language for describing Web services and how to access them.

What is WSDL?

• WSDL stands for Web Services Description Language
• WSDL is written in XML
• WSDL is an XML document
• WSDL is used to describe Web services
• WSDL is also used to locate Web services
• WSDL is a W3C recommendation

WSDL1.1 and WSDL2.0

The WSDL Document Structure

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

Element	Description
<types>	A container for data type definitions used by the web service
<message>	A typed definition of the data being communicated
<portType>	A set of operations supported by one or more endpoints
<binding>	A protocol and data format specification for a particular port type

The main structure of a WSDL document looks like this:

<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 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.

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WSDL Ports

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

It describes 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.

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WSDL Messages

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

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

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WSDL Types

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

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

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WSDL Bindings

The <binding> element defines the data format and protocol for each port type.

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