In the same 1971 seminar where we studied Algol-68, we had to read and
write a short paper on the 1970 Codd paper on relational theory, which had
only been out for about a year. The professor running the seminar noted
that Codd proved that the relational model worked, but didn't guarantee
that it worked efficiently enough to be implementable without immense
computer resources, which of course became available.
--
Mike Nolan