  Integrity checking is a crucial issue, as databases change their instance all
the time and therefore need to be checked continuously and rapidly. Decades of
research have produced a plethora of methods for checking integrity constraints
of a database in an incremental manner. However, not much has been said about
when to check integrity. In this paper, we study the differences and
similarities between checking integrity before an update (a.k.a. pre-test) or
after (a.k.a. post-test) in order to assess the respective convenience and
properties.
