Workflow systems, BPEL and the like focus on the sequence of activities at a single 'system' or party.  However, interesting business processes involve two or more parties (and the systems they run on) that interact with each other. Various attempts have been made to express the interactions between the parties of a distributed business process in an XML form. The most notable of these are perhaps the Business Process Schema Specification, originally developed jointly between UN/CEFACT and OASIS as part of the ebXML project and now being actively evolved by an OASIS Technical Committee, and W3C WS-Choreography. The approach taken in BPSS is to build in a small amount of structure corresponding to a common pattern for business process interactions. A different angle is being taken by the W3C group developing WS-Choreography, which is aimed at being a general Choreography description language (CDL). This work is on track to become a W3C Recommendation by mid 2005.

 

Choreology has been active in this group for two reasons. Firstly we have a general interest in techniques for describing or specifying business application protocols. Secondly we are seeking to ensure that it is both possible and easy to describe which messages are part of which transaction, and the different ways in which a choreography can continue when a transaction completes. The use of transactions is important in distributed business processes for the following reasons:

 

a)  to make sure that the different parties involved can end up with assured agreement on what commitments they have agreed to, and the changes in information that have been agreed,

 

b) so that one party can coordinate the actions of one, or more, other parties according to its application requirements (i.e. business rules), and

 

c) so that the effects of any faults and exceptions that do occur can be contained.

 

Thus the use of an underlying transaction protocol and a simple scheme for showing its use in the choreography language can make the writing, and performance, of business processes much easier compared to having to do everything each time with each different application protocol that is described.