
Appendix B ◾ 391
Figure B.17 illustrates the classification of tuples. Here the tuples relating to
John are unclassified while the tuples relating to Paul are secret. Furthermore the
tuples relating to Mary are top secret. Note that we have also assigned tuple level
labeling to the relation DEPT. Here again we can classify collections of tuples
taken together at say the top secret level.
Figure B.18 illustrates element level classification. is is the finest level of gran-
ularity. For example, we classify the salary of John at the confidential level while the
EMP: Level = Secret DEPT: Level = Unclassified
SS# Ename Salary D# D# Dname Mgr
1 John 20K