WSDL objects

Web Services Description Language (WSDL) is based on the XML programming language. WSDL is used to describe the services a business offers and to provide a way for individuals and other businesses to access those services electronically.

WSDL is the language used by UDDI (Universal Description, Discovery and Integration), an XML-based worldwide business registry. UDDI provides a platform-independent framework for describing services, discovering businesses, and integrating business services by using the Internet.

Web services

A WSDL document is simply a set of definitions. A WSDL document describes a web service—a collection of communication endpoints capable of exchanging messages. It does so using these major elements:

• <portType> The operations performed by the web service.
• <message> The messages used by the web service.
• <types> The data types used by the web service.
• <binding> The communication protocols used by the web service.

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.

Web services can convert your applications into web applications. Web services share business logic, data and processes. The applications interface with each other, not with users. For example, one purchase-and-ordering application could communicate to an inventory application that specific items need to be reordered.

Web services allow organizations to communicate data without intimate knowledge of each other's IT systems behind a firewall.

Related concepts

XML

Extensible Markup Language, a specification developed by the W3C. XML is designed especially for Web documents. It allows designers to create their own customized tags, enabling the definition, transmission, validation, and interpretation of data between applications and between organizations. An XML schema describes the structure of an XML document.

SOAP

Simple Object Access Protocol, a lightweight XML-based messaging protocol used to encode the information in a web service request and response message before sending it over a network. SOAP messages are independent of any operating system or protocol and may be transported using a variety of Internet protocols, including SMTP, MIME, and HTTP.

UDDI

Universal Description, Discovery and Integration, a Web-based distributed directory that enables businesses to list themselves on the Internet and discover each other, similar to a traditional phone book's yellow and white pages.

XML is used to tag the data, SOAP is used to transfer the data, WSDL is used for describing the services available, and UDDI is used for listing what services are available.