[FOM] Correction to "A question about modal models"
Dana Scott
dana.scott at cs.cmu.edu
Fri Jun 12 00:12:40 EDT 2009
I forgot for a moment what "finite meets" has to
entail: the empty meet, which equals 1.
Hence, if L is a complete Boolean algebra, then
the two degenerate sublattices closed under all
finite meets and arbitrary joins are thus:
H = {0, 1} and H = L.
The modal operators defined by either of these H
are trivial.
Of course -- just as with ordinary topological
spaces -- we can generate an H by closing a given
set, first, under finite meets, then, under arbitrary
joins. This gives many non-degenerate examples.
Finding "interesting" examples is another question.
-- Dana Scott
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