With Web services bringing together an array of different users, applications and services, their interactions must be choreographed, so the World Wide Web Consortium (W3C) has published the first in a series of drafts for the Web Services Choreography Description Language, Version 1.0 (WS-CDL).
The consortium, created to leverage the Web through common protocols to promote evolution and interoperability, said WS-CDL will provide a set of rules governing how different components can act together and in what sequence for a flexible, systemic view of the process.
W3C spokesperson Janet Daly told TechNewsworld that the consortium hopes to release at least two more drafts of WS-CDL and put out a last call for input by the end of the year.
“That’s fast, but the group is ambitious,” Daly said.
Web Ballet
The W3C said the WS-CDL is needed to complement end-point languages, such as Business Process Execution Language (BPEL) and Java, providing them with the global model required to ensure that end-point behavior, also described as “rules of engagement,” is consistent across cooperating services.
Daly said that whereas BPEL and Java are complete programming languages, WS-CDL is simply a choreography description language.
“They’re both very important,” she said. “BPEL/Java directs individual behavior at one point in the multipoint transaction. CDL dictates how they move together, whether they can do so in parallel, what needs to happen first before something else can happen and those kinds of things.”
She used the analogy of professional dance, in which executed steps are dictated by BPEL or Java as individual dancers, with WS-CDL describing the dance and how the different dancers interact with one another. The “choreography” name for the Web services language actually comes from that analogy, according to Daly.
Web Services March
Yankee Group senior analyst Dana Gardner said standards, interoperability and adoption of Web services all rely on each other, but he added that the standards are presently most important.
“Web services really depends on interoperability, and that comes from standards, so it’s really an ongoing march. You never really reach the destination, but you get closer,” Gardner told TechNewsWorld.
The analyst added that choreography and the ability to assemble services into a business process or workflow or aggregated interface represents the next level for Web services.
Help Instead of Hype
The W3C’s Daly said that after suffering from overly aggressive Web-services marketing from some vendors, customers now are driving the embrace of open standards and the refusal to work with proprietary ones.
“With the hype dying down, there’s more input from users, and that means things are better matched to what’s developing,” Daly said.
She said that although it will still take time to deal completely with such issues as security in Web services, the W3C is seeing more stability in its specs and is benefiting from more input from various companies and communities.
Iterative Approach
Gardner said that while there is some rivalry among various Web services specifications and standards, it is too soon in the evolution of the technology to know exactly where the different standards will settle.
“BPEL and CDL are really at a point where they are pieces of a puzzle that may not fit together well yet,” he said. “These are complex undertakings, and they involve a lot of different technologies and players.
“There’ll be an iterative approach to making this stuff behave well in concert,” he added.
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