There are lots of potential uses for machine readable specifications so you would think that every major real world artifact like long-lived hardware and software systems, protocols, languages, etc. would have a formal specification that is used by all teams extending the design, creating new implementations, testing/verifying the system, verifying code that uses the system, doing security analyses or any of the other potential uses. But, in practice, this is usually not true: most real world systems do not have a well tested, up to date, machine readable specification.