External Behaviour of Systems of State Machines with Variables

This is the author’s version. The official appeared in LNCS 7480. This tutorial is an introduction to compositionality and externally observable behaviour. To make it easier to understand system descriptions, traditional process-algebraic languages have been replaced by state machines represented as annotated directed graphs. Emphasis is on a novel way of treating local variables, and on the Chaos-Free Failures Divergences semantics. Even so, big themes that are not tied to any particular semantics are pointed out where possible. Other semantic models are introduced briefly. Most important verification methods facilitated by compositionality are mentioned with pointers to literature. Mathematical details are given less attention but not left out altogether. Throughout the tutorial, important principles are summarized in framed pieces of text.