Encapsulating concurrency with Early-Reply

Component methods often produce their final parameter values long before the method body is ready to terminate. To minimize client blocking, Early-Reply can be used to forward invocation results to the caller as soon as they are (safely) available. After executing Early-Reply, the method remainder and the client caller can proceed concurrently, modulo synchronization constraints. The prime motivation for Early-Reply, then, is to improve performance factors such as response time and resource utilization.Early-Reply received previous attention as a construct for explicit concurrent programming. It's value for sequential programming, however, has not been widely recognized. The present research supplies a formal treatment of Early-Reply as a basis for concurrent execution of sequential programs. In particular, we reformulate Early-Reply under local proof obligations that encapsulate concurrency as a (temporal) unit of information hiding. The upshot is that software developers can use Early-Reply to exploit the performance benefits of concurrent execution, without compromising the reasoning benefits of sequential programming.