OPEN UNIVERSE: One possible view of the relationship between the data in a
database and the subject matter thus described (See CLOSED UNIVERSE).
In the OPEN UNIVERSE, there are certain facts which are true in the real
world, and could be asserted in the database, but are not. Thus a search
for a fact in a database that comes up empty does not assert that the fact
is false in the real world.
CLOSED UNIVERSE: One possible view of the relationship between the data in
a database and the subject matter thus described (See OPEN UNIVERSE).
In the CLOSED UNIVERSE, a database that is capable of storing a certain
fact about the real world, but has no such fact stored, is implicitly
denying the truth of that fact.