A set S, a subset of D, is Scott-closed if
(1) If Y is a subset of S and Y is
directed then lub Y is in
S and
(2) If y #@= s in S then y is in S.
I.e. a Scott-closed set contains the
lubs of its
directedsubsets and anything less than any element. (2) says that S
is downward
closed (or left closed).
(1995-02-03)