I had an interesting conversation the other day at a client who was very interested in an event driven approach towards integration versus the traditional centralized orchestration model. The discussion identified that within the event driven model, the state of the process would be maintained in the message versus in the singular centralized orchestration (BPEL). Both solutions have their strengths and drawbacks. One of the big drawbacks that was discussed was in monitoring/management. Operations likes to have a centralized, process oriented depiction of what is occurring. The event model we discussed would spread out the process across a wide range of intermediaries and the message would be updated along the way. Not an ideal situation if viewing from this perspective. Whereas, the BPEL Service provides a more centralized view/approach.
An option for Event Driven would be to utilize an auditing interceptor that would provide a centralized view/update of the process execution. Operations could then monitor this service to get the depiction they preferred.
A strength of the BPEL approach was in the composing of task services or business processes. An event approach everyone thought would not be as easy to compose, however the scalability/performance benefits is very intriguing. This discussion will continue and hopefully draw out distinct patterns on when one approach is better than another.