The World Wide Web Consortium has published the first draft of the Web services Choreography Description Language (WS-CDL). WS-CDL is targeted at coordinating interactions among Web services and their users. WS-CDL promises to be a necessary component for BPEL or other programming languages used to model business processes.

The WS-CDL specification defines peer-to-peer collaboration between Web service participants. A user of a Web service, automated or otherwise, is a "client" of that service. Users may be other Web services, applications and human beings. In WS-CDL, a set of client interactions may be related over time in a "collaboration group." A collaboration group could be for example, a set of components that make up a business transaction or a database transaction.

The future of e-business applications is in the loosely coupled, decentralized environment of the World Wide Web. This environment requires the ability to perform long-lived, peer-to-peer collaborations between the participating services, within or across the trusted domains of an organization. Applications that implement WS-CDL can accomplish this shared business goal, as the Working Group developed its requirements document to consider both broad practical business needs and sound theories.

From World Wide Web Consortium Publishes First Public Working Draft of Web Services Choreography Description Language 1.0
Referenced Wed Apr 28 2004 17:31:35 GMT-0600

Interestingly enough, WS-CDL is based on Pi Calculus. I used to be a formal methods guys and have studied Pi Calculus and its predecessor, CCS before. Never imagined that they'd show up in Web services.

I believe that there is hope that WS-CDL and BPEL will be complimentary. We'll see.