Symmetric intertask communication

Abstract

We argue for the need of supporting a symmetric select construct, in which entry calls as well as accepts can be alternatives. We present several situations in which a symmetric select leads to a more natural programming style. We show that several semantic principles are violated by a nonsymmetric select, while being satisfied by a symmetric one. In particular, the suggested symmetric intertask communication mechanism is fully abstract and composable, and has a distributed termination rule which reduces the risk of deadlock. Our discussion is in terms of Ada™.