Though WSCI is more famous, the official choreography model blessed by the W3C’s Choreography Working Group is WS-CDL, whose latest working draft was released by the W3C in December 2004.[*] WS-CDL is a brand-new XML process contract language that provides a standard way to specify technical contracts that capture (from a global viewpoint) the common observable behavior of autonomous interacting participants. The distinguishing characteristics of WS-CDL are the following:
WS-CDL choreography is seldom confined to applications on a corporate intranet. Rather, the participants are usually from different companies all over the world. Participants use web services to communicate with one anothe, and publish their service interfaces in a WSDL. (WS-CDL supports WSDL Versions 1.1 and 2.0.)
WS-CDL choreography may be global, but WS-CDL does not prescribe a global, centralized control engine to coordinate or manage participant interactions. Instead, each participant has its own engine that executes the participant’s business process. The process, in turn, is required to obey the rules of interaction required by the WS-CDL choreography.
A company’s business process can have many steps, but
WS-CDL is concerned only with the public face (e.g., in a BPEL
invoke activities for
relevant partner links).