Further Operators

Abstract

This chapter completes the CSP language by introducing three operators that allow one process to hand control on to another. In sequential composition P;Q this happens when the first process terminates successfully via a special action ✓. In interrupt $P\mathrel {\mathord {\triangle }}Q$ this happens when the environment communicates an initial action of Q, and in throw $P\mathop{ \varTheta _{A}}Q$ any occurrence of an action in A within P counts as an exception which hands control to Q. We study in particular the relationship between termination and parallel composition, and the effect of termination on the semantic models seen in earlier chapters.