Web Service Choreography

Web Service Choreography (WS-Choreography) is a specification by the W3C defining a XML-based business process modeling language that describes collaboration protocols of cooperating Web Service participants, in which services act as peers, and interactions may be long-lived and stateful.

The underlying intuition behind the notion of choreography can be summarised as follows.

“Dancers dance following a global scenario without a single point of control"

Web Service Choreography leverages the power of Web services to allow entities to create business processes that mirror today's dynamic and ever-changing business needs. Organizations can expose their application software and resources as Web services so that others can dynamically find and use them in their business processes. Creating a business process requires not only a clear definition of collaboration patterns of all its components but also a way of depicting standard B2B interactions. WS-Choreography addresses the vision of true Web service coordination and collaboration by:

1. Providing practical models for dynamic, reusable and scalable process compositions and choreography
2. Addressing technical completeness/correctness/executability issues
3. Enabling more dynamic, semi-automated composed processes
4. Enabling the incorporation of semantics

History

"Many presentations at the W3C Workshop on Web services of 11-12 April 2001 pointed to the need for a common interface and composition language to help address choreography. The Web Services Architecture Requirements Working Draft created by the Web Services Architecture Working Group also lists the idea of Web service choreography capabilities as a Critical Success Factor, in support of several different top-level goals for the nascent Web services architecture"[1].

The problem of choreography was (and still is) of great interest to the industry during that time efforts such as WSCL (Web Service Conversation Language) and WSCI (Web Service Choreography Interface) were submitted to W3C and were published as Technical Notes. Moreover complementary efforts were launched[2]:

• BPML, now BPMN
• BPSS by ebXML[3]
• WSFL by IBM
• XLANG by Microsoft
• BPEL4WS by IBM, Microsoft and BEA

"In June 2002, Intalio, Sun, BEA and SAP released a joint specification named Web Services Choreography Interface (WSCI). This specification was also submitted to W3C as a note in August 2002. W3C has since formed a new Working Group called Web Services Choreography Working Group within the Web services Activity. The WSCI specification is one of the primary inputs into the Web Services Choreography Working Group which published a Candidate Recommendation on WS-CDL version 1.0 on November 9th, 2005"[4]. "XLang, WSFL and WSCI are no longer being supported by any standard organization or companies BPEL replaced Xlang and WSFL WSCI was superseded by WS-CDL"[5].

See also

• BPEL - OASIS standard
• Web Services Choreography Description Language - A Description Language based on the notion of Choreography

External links

• Web Service Choreography Description Language - W3C specification for WS-Choreography
• Web Service Choreography Description Language: Primer -
• Web Service Choreography Interface (WSCI) 1.0 - specification by Intalio, Sun, BEA and SAP; input into WS-Choreography
• Web services choreography in practice - Motivation and description of WSCI
• Service Choreographies - Site promoting the concept of service choreography as a basis for service-oriented systems design. The site also describes a language for modeling choreographies on top of WSCI, namely Let's Dance.