FOM: Reply to Simpson

Vaughan R. Pratt pratt at cs.Stanford.EDU
Sun Nov 9 02:37:38 EST 1997

>From: simpson at
>I wonder if Vaughan would care to estimate the half-life of Chu
>spaces.  Is there any reason to think that it will exceed 5 years?

The concept in its current form is around 20 years old, Chu spaces
having been studied by Peter Chu in the 1970's.  I first heard about
them in 1989 but did not grasp their significance until 1992.  At a
conference I was at this summer four people presented papers on them.

The inspiration for Chu spaces goes back to George Mackey's 1945 thesis
(and it's been suggested they be called Chu-Mackey spaces).  They can
be understood as a unification and generalization of the ostensibly
dissimilar notions of topological space and inner product space, so in
that respect at least one could say that they're a century old.

>I'm not trying to denigrate linear logic; rather, I'm trying to goad
>Vaughan into explaining the general intellectual interest of Chu spaces
>and linear logic, if they have any.

Which parts were unclear in the three paragraphs on linear logic in my
post dated Thu, 06 Nov 1997 13:59:14 -0800?

For Chu spaces my message of Thu, 23 Oct 1997 17:01:18 -0700 would do,
but I appreciate that that was a fortnight ago and long to boot.  I'll
follow up this message with a paragraph informally defining them and
two paragraphs on some interesting aspects.


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