Database Reference
In-Depth Information
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 into an MLS relation R, the insertion operation is implemented
as follows [32]:
• 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 of the insert statement.
• Step 3: the security level of the primary key will be equal to
the security level of the subject that runs the insert operation.
• Step 4: insert the new tuple into the multilevel relation.
Figure 3.7 illustrates the flow chart for the insertion operation in the
Smith-Winslett 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
PK
= L(user)
Insert the row
End
Figure 3.7
Flow chart for insertion operation in Smith-Winslett model.
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