A proposed WS-Reliability standard defines a method for guaranteeing delivery of XML documents in business communications.
WS-Reliability, if accepted as a standard and adopted by Web services providers, will let a company ensure that a message sent between two different applications is delivered reliably. For example, a company could send a purchase order to a supplier via a Web service and be guaranteed that the message was either successfully delivered and performed its function, or that the transmission failed.
Currently, businesses working with Web services can make sure their communications are reliable using specialized software or other established products. WS-Reliability seeks to create a standardized method that is widely supported.
The specification, which will be submitted to a standards body in a few weeks, was written by a number of companies, including Fujitsu, Hitachi, NEC, Oracle, Sun Microsystems and Sonic Software.
WS-Reliability builds on top of the Simple Object Access Protocol (SOAP), one of the fundamental Web services protocols that defines how XML (Extensible Markup Language) documents are transported over a network. Layering WS-Reliability on top of SOAP gives businesses that deploy Web services the flexibility to use different network transport protocols, representatives from the authoring companies said.
The contributors said that reliable messaging is a key piece in making Web services industrial strength, particularly for asynchronous communications between different parties. Traditionally, business applications rely on a request/response form of communication, which demands that different applications synchronize using the same underlying protocols and development models.
The "loosely coupled" model that Web services facilitates is better suited to multistep business processes where an XML document moves from one step in the business workflow to the next, company representatives said.
For more long-running, asynchronous, document-oriented business processes, "you need assurances that when there are multiple messages, you can manage the quality of service," said Tom Rutt, a consulting engineer with Fujitsu.
Ron Schmelzer, an analyst at ZapThink, said WS-Reliability tackles one of the long-standing hurdles to Web services adoption, which also include security, management and transactions.
"The big problem with the way people are implementing Web services today is that they are using pretty brittle protocols like HTTP (hypertext transport protocol). It's OK for your browser, but no one in their right mind is going to implement a travel reservation booking system with that," said Schmelzer. "The application had better succeed or reliably fail. It shouldn't be that the server didn't respond."