Sun Microsystems and a group of software vendors are proposing to add another standard to the recipe for building Web services.
On Wednesday, the companies detailed a specification that would allow developers to "choreograph" events and transactions that take place between computers when applications and services are accessed over the Internet. The specification is called the Web Service Choreography Interface (WSCI), and it is designed to work with Web services based on the standard data format XML (Extensible Markup Language).
Joining Sun in drafting and publishing the specification are software makers SAP AG, BEA Systems Inc. and Intalio Inc.
For Web services that make use of several existing Web-based applications, the specification aims to define a standard way for developers to describe which actions must occur and in what order they must take place, so that the Web service they are building can process information in an orderly manner, said Karsten Riemer, an XML architect with Sun.
For example, a Web site where users can book airline tickets online might require an application that combines existing Web services for various tasks, such as determining whether the user is a member of a frequent flier program, figuring out which airlines fly to the destination being requested, and checking that the user has sufficient funds in his or her bank account to purchase the ticket.
Technologies for choreographing interaction between Web services are not new, and WSCI is not the only standard to have been proposed, noted Mike Gilpin, a research fellow with Giga Information Group Inc. Intalio, which makes application infrastructure software and developed much of the WSCI specification, has been using a technology related to WSCI in products that it already sells.
"There are a bunch of these things around," Gilpin said.
In fact, while several standards used to create and deploy XML-based Web services have already been agreed upon by vendors, many have come up with their own technologies for choreographing Web services, a process also known as workflow orchestration.
IBM Corp.'s MQ Series Workflow tool uses an orchestration specification called WSFL (Web Services Flow Language). Microsoft Corp. has its own technology called XLang which is used by its BizTalk Server. A third technology used by some companies for similar purposes is BPML (Business Process Modeling Language), Gilpin said. Intalio is a lead member of the group that developed BPML.
Sun said it plans to release the test version of a developer tool later this week that would include support for the specification. Called the Sun ONE WSCI Editor, the graphical editing tool should help developers to choreograph a series of transactions in a Web service using WSCI, Sun said.
If WSCI is accepted by a wider group of vendors, it would be added to the existing alphabet soup of XML-based Web services standards such as WSDL (Web Services Description Language), SOAP (Simple Object Access Protocol) and UDDI (Universal Description, Discovery and Integration). But there are signs that it could face resistance as individual software vendors promote their own technologies.
"Unlike some of the other XML standards for Web services like SOAP and WSDL, there is less consensus across the industry about which of these formats should be the one to win," Gilpin said. "There's more motivation to be incompatible because there are various products that support each technology."
The technical details of WSCI have been posted on the Web at the various participating vendor Web sites and are available for public review and comment. After a public review period, WSCI will be submitted to an industry standards body for consideration, Sun said. The companies supporting WSCI have not decided which standards body the specification will be submitted to. Some options, according to Sun, include the W3C (World Wide Web Consortium) as well as OASIS (Organization for the Advancement of Structured Information Standards).
The WSCI specification is available as a free download from the Web sites of each co-author of the technology, and can be found online at: http://dev2dev.bea.com/techtrack/wsci.jsp; http://www.intalio.com/wsci; http://ifr.sap.com/wsci; and http://www.sun.com/software/xml.