Chapter 5: Established SOA Standards

Overview

In most cases, you use the following open-standard technologies when developing a Web service.

• Web Services Description Language (WSDL) is an XML format for describing how to access a service.

• SOAP is an XML format for transmitting data to and from a Web service. The runtime message includes business data (as defined in the WSDL definition) and may contain Quality-of-Service (QoS) details too, including (for example) the security details needed to gain access to the service. Although QoS details may be defined in the WSDL definition, those details are increasingly likely to be defined only when a system administrator uses an SOA runtime product to configure the message.

  SOAP was once called Simple Object Access Protocol and is now known only as SOAP.

• Universal Description, Discovery, and Integration (UDDI) is a set of rules for registering and retrieving details about a business and its services. Some of the registered details are in the form of WSDL definitions.

WSDL and SOAP have become enormously important, with UDDI less so. The three standards are interrelated to some extent. Figure 5.1 depicts the relationship.

Figure 5.1: Established SOA standards

As the figure suggests, a WSDL definition describes a Web service. A UDDI-compliant service registry can help companies to discover that description. At run time, SOAP-based messages carry business data that conforms to the description.

The World Wide Web Consortium (W3C) is the sponsoring organization for WSDL and SOAP. The Organization for the Advancement of Structured Information Standards (OASIS) has an equivalent role for UDDI.