Implementation of MLS/DBMS Models - Multilevel Security for Relational Databases - page 48

Get user class L(user)

Set i = 1

Get t i that satisfy P

i = i + 1

No

t i [TC]= L(user)

Ye s

Delete ti i

End

Figure 3.9 Flow chart for delete operation in Smith-Winslett model.

tuples from an MLS relation R, the selection operation is implemented
as follows [33]:

• Step 1: get the security level of the subject that runs the select
operation.
• Step 2: get all tuples that have a security level below or equal
to the security level of the subject that runs the select opera-
tion and that satisfy selection condition P.

Figure 3.6 illustrates the flow chart for the selection operation in the
MLR model.

3.5.2 Insert Operation Procedure

The SQL statement for the insert operation is described as follows:

INSERT
INTO R [A 1 ,A 2 ,...,A n ]
VALUES [a 1 ,a 2 ,...,a n ]