422 ◾ Appendix D
Consider a database that consists of a relation SHIP whose attributes are ship
number, name, class, date, and MISSION, with mission number as its primary
key. e content-based constraint that classifies all SHIP values with the name
Josephine as secret is expressed as
SHIP.sname = "Josephine"— — > Secret.
A user at login security level of, for example, Confidential enters the following
data to insert a tuple into the SHIP relation:
Insert SHIP values ("SSN 729", "James","Thomsen","MR1800").
at is, the ship number for James is SSN729, his captain is omsen, and his
mission record number is MR1800.
e update processor will receive this insert and retrieve the constraints associ-
ated with the SHIP relation that specify a level gre