Web Services Description Language

The purpose of this article is to provide a very brief description of the Web Services Description Language (or WSDL) as well as provide some resources of where to more detailed information and tutorials on the language.
WSDL is simply an XML file.  However, this file has a specific structure that can provide useful information to a user.  Specifically, WSDL is used to describe the functionality offered by a Web service.
This language is broken up into 5 parts, 3 of which (types, messages, and port type) are abstract definitions which define the interface, and the other 2 (binding and service) which are concrete details of how aforementioned abstract interfaces map to messages on the wire.
Very briefly, the 5 parts are described below:

• Types – a container for abstract type definitions defined using XML Schema.
• Message – a definition of an abstract message that may consist of multiple parts, each part may be of a different type.
• PortType – an abstract set of operations supported by one or more endpoints; operations are defined by an exchange of messages.
• Binding – a concrete protocol and data format specification for a particular PortType.
• Service – a collection of related endpoints, where an endpoint is defined as a combination of a binding and an address (or URI).

These elements together make up a WSDL definition.

Resources
For more information on WSDL and Web Services please refer to these websites:

• Understanding WSDL
• Web Services Description Language
• Web Service
• Web Services Description Language (WSDL) 1.1

Tutorials
For some tutorials about WSDL and Web Services please refer to these websites:

• WSDL tutorial
• Web Services tutorial