
Shepherdson
The
Relation
between the Closed World
Assumption
and the
Completed
Database
The closed world assumption, cwa(P), and the completed database, comp(P),
are superficially similar. They are both examples of reasoning by default, as-
suming that if some positive piece of information cannot be proved in a certain
way from P, then it is not true. But for cwa(P), the notion of proof involved is
that of full first order logic, whereas for comp(P), it is "using one of the
program clauses whose head matches the given atom." At first sight this is a
narrower notion of proof so that more ground atoms should be false under
comp(P) than under cwa(P) ...