Thirty years ago, in September 1971, the ``ADJ Group'' (Joe
Goguen, Jim Thatcher, Eric Wagner, and Jesse Wright) was founded
at IBM Research.  In this talk I will sketch the history of the
group, and give an overview their technical contributions in the
area of data type specification (making considerable use of
hindsight).  In brief, my judgment is that we produced a nice,
even elegant, theoretical treatment of data type
specification, but we, and perhaps those who came after us,
failed to produce a workable methodology
for developing actual data type and program specifications.
I will close with some remarks on my current attempts to find
ways to improve this situation.