Richard Seroter of Microsoft has published a useful blog posting at http://blogs.msdn.com/richardbpi/archive/2005/10/27/485696.aspx in which he describes one technique for passing messages of any type through a BizTalk orchestration. Here is some further information to supplement what he has written.
Here's a little useless trivia. Just under a month ago (27th September to be precise), The US Patent & Trademark Office granted patent 6,951,022 to Microsoft Corporation. Filed on March 14th 2001, it had taken a little while to go through the system. The patent was for ...drum roll please... "Delegate-based event handling". So now we really can be sure that's one C# feature Java won't have for a very long time!
In Microsoft's Windows Workflow Foundation (WF), rules are executed through a sequential, rather than an 'inferencing' engine. Although WF rule processing bears a superficial resemblance to rule processing in the Microsoft Business Rules Engine (MS BRE), there are profound differences. This article attempts to explain the fundamental differences, and to provide some insight into the strengths and weaknesses of each approach.