Integrating formal methods into the development process

It is shown that integrating formal specification and verification with development is faster and more cost-effective than doing the steps separately or in parallel. This case study demonstrates their application in a security context and documents their use in several phases of development, starting from the requirements of a terminal serving a security officer, on through formal requirements and design expressed as state transitions, to detailed design specifications and proofs that these agree with higher-level specifications, stopping just before code-level verification (due to complications typical of such projects). The effects of verification on this particular project are addressed.<>