Hi,
In my research, I deal with filters.
A filter is a non-empty set whose members are
supersets of a particular given set. As an example, consider
the set X = {1, 2, 3}. The filter generated by the set {1} has
the following members: {1}, {1, 2}, {1, 3} and X.
Note that any filter is a subet of the powerset of
X, whose members are the empty set, {1}, {2}, {3}, {1, 2}, {1, 3},
{2, 3} and X.
Thanks!
Cheers,
Wen Shih