Let
represent fixed subsets of a space
Let the complement of the set
be 
and let
A constituent of the set S is the intersection of the
for
to
where
or 1 ie any intersection
The constituents are all disjoint and have intersection equal toIf all the constituents are non empty the setsare said to be independent.
Example: Let A, B and C be subsets of a space S. The constituents of
with respect to
and
are
