Identifying standard message exchange patterns
When we talk about Message Exchange Patterns, or MEPs, we're considering the direction and timing of data between the client and service. How do I get into the bus and what are the implications of those choices? Let's discuss the four primary options.
Request/response services
This is probably the pattern that's most familiar to you. We're all comfortable making a function call to a component and waiting for a response. When a service uses this pattern, it's frequently performing a Remote Procedure Call where the caller accesses functionality on the distant service and is blocked until either a timeout occurs or until the receiver sends a response that is expected by the caller.
As we'll see below, while this pattern may set developers at ease, it may encourage bad behavior. Nevertheless, the cases where request/response services make the most sense are fine-grained functions and mashup services. If you need a list of active contracts that a hospital...
