Implementation of MLS/DBMS Models - Multilevel Security for Relational Databases - page 37

where R is an MLS relation, A 1 ,A 2 ,...,A n are the attributes from
R, and a 1 ,a 2 ,...,a n are values from domains of A 1 ,A 2 ,...,A n .
If a subject with the security class level L runs a command to insert a
tuple in an MLS relation R, the insertion operation is implemented
as follows [30]:

• Step 1: get the security level of the subject that runs the insert
operation.
• Step 2: if the attribute is included in the attributes list in the
insert statement, this attribute will be set to its value from the
values list in the insert statement.
• Step 3: the security level of all attributes will be equal to the
security level of the subject that runs the insert operation.
• Step 4: insert into single-level relations, with the security level
equal to the security level of the user, values that are included
in the values list of the insert statement and that correspond
to the attributes of these single-level relations.

Figure 3.2 illustrates the flow chart for the insert operation in the
SeaView model.

Get user class L(user)

Set i = 1

A i ∈ R [A i ]*

i = i + 1

No Ye s

A i = null A i = a i

C i = L(user)

Execute the insert statement

End

Figure 3.2 Flow chart for insertion operation in SeaView and Jajodia-Sandhu models.