Back in Chapter 7, Planning Service-oriented BizTalk Solutions, we looked at Message Exchange Patterns (MEP) and evaluated differences between them. We concluded that asynchronous patterns can be more service-oriented and loosely coupled than synchronous patterns. However, there are cases where you want a single business process to accommodate invocation by either mechanism. In certain scenarios, the caller has no interest in the outcome, but in other situations, the caller requires resolution about the service outcome. You could choose to build two distinct processes that each support a distinct MEP, but this is fairly inefficient and challenging to maintain. What if we want to build a BizTalk orchestration with the least amount of effort required that can be invoked either synchronously or asynchronously?