The Model Checker SPIN Written by Gerard J. Holzmann Presented by Chris Jensen

Introduction Description Verification system for models of distributive, concurrent systems Goals Intuitive code-like notation for specifying design choices unambiguously without implementation detail Notation for expressing correctness requirements Methodology for establishing consistency between design choices and correctness requirements

How It Works Iterative refinement of model behavior refinement through simulation, verifier generation Correctness properties are expressed in linear temporal logic (LTL) Converts this to a Buchi automaton, produces a synchronous product of the claim and the BA representing the the state space If the language accepted by the resulting BA is empty, the claim is NOT satisfiable, otherwise, it IS satisfiable Correctness is verified by demonstrating a lack of undesirable behavior Worst case global reachability graph has size of Cartesian product of all component systems

How It Works (2) Design specifications are expressed in Process Meta Language (PROMELA) Devised to permit only finite range of component state spaces State space is traversed with a DFS using state space compression and bit-state hashing to manage otherwise exponential memory requirements

Interesting Points Distinction between behavior and requirements on behavior Requirements and behaviors are checked for internal and mutual consistency Iterative refinement of correctness properties