Tracking design changes with formal machine-checked proof

Abstract

Design are often modified for use in new circumstances. If formal proof is to be an acceptable verification methodology for industry, it must be capable of tracking design changes quickly. We describe our experiences formally verifying an implementation of an ATM network component, and on our subsequent verification of modified designs. Three of the designs verified are in use in a working network. They were designed and implemented with no consideration for formal methods. This case study gives an application of the difficulties in formally verifying a real design and of subsequently tracking design changes.