Re: types as set of values

This reponds to Giuseppe Castagna's request (below) for old
references on type ideas. The NATO Science Committee Conference
"Techniques in Software Engineering" In Rome, October 1969
distributed a book of "Working Material Volume II" dated
September 1969. It includes 2 papers:

  - "The programming language PASCAL and its design criteria"
by N. Wirth

  - "Proposed language extensions to aid coding and analysis of large
programs" by E. S. Lowry. It was also published with the same
title as IBM Poughkeepsie Lab Technical Report TR 00.1940-1,
November 21, 1969.

Both papers present the idea of types as sets of values. In my
paper they were called ranges rather than types. The extensions
in my language "Extended Systems Language" were built onto the
"Basic Systems Language" used internally at IBM and later called

I gather that Niklaus Wirth and I were both developing the ideas
independently during 1968.

I continued  by including more comprehensive executable set
referencing and removing machine oriented ideas in order to
improve simplicity of expression in an integrated programming and
data base language. That was first published as "PROSE
Specification" IBM Poughkeepsie Lab Technical Report TR 00.2909,
Nov 1977.

As far as I know there are only a few dozen people anywhere who
have experience with language as advanced as that from a
simplicity point of view. A brief description is given in
"Misdirections in Information Technology" on my web site. I asked
US Senator John Kerry to check on the delay. The main question
was whether anyone working in the US Federal Government has
experience using software technology which allows for simplicity
as advanced as what was designed over 25 years ago. He asked 5
government agencies and none has found anyone that advanced. I
have been using the "test" at the end of the "Misdirections in
Information Technology" paper.

Further work eliminating needless complexity imposes constraints
on the structure of basic data objects. It is similar to the way
eliminating vibration from cars constrains wheels to be round. I
conclude that currently used languages are "square wheel"
unreasonable. There is a $25K challenge on my web site related to
that issue.

Ed Lowry
Bedford Mass USA

Giuseppe Castnaga writes:

    interpreting a type of a language as the set of the _values_
of the language that have that type is an idea that belongs to
the type folklore. I am trying to trace back this idea, and the
oldest paper I was able to find that mentions it is the Amadio
and Cardelli paper on subtyping recursive types, but I am pretty
sure that older references must exist. Has anyone a better (i.e.
older) reference?

Thanks in advance