Database Reference
In-Depth Information
Get user class L(user)
Set i = 1
t
i
[TC] = L(user)
Ye s
No
Delete ti
i
i = i + 1
t
i
[TC]
≻
L(user) and
t
i
[C
PK
] = L(user)
Ye s
No
Mark to be deleted
by high user
End
Figure 3.12
Flow chart for delete operation in an MLR model.
3.5.5 Uplevel Operation Procedure
The SQL statement for the uplevel operation is described as follows:
UPLEVEL R
GET [A
1
,A
2
,...,A
n
] FROM [C
1
,C
2
,...,C
n
]
WHERE P
where R is an MLS relation,
A
1
,A
2
,...,A
n
are the attributes from R,
C
1
,C
2
,...,C
n
are the classification level of
A
1
,A
2
,...,A
n
, and P
is an uplevel condition that defines the tuples that are to be uplev-
eled. A user on the security level L issues an UPLEVEL command
to indicate that he believes the tuples in the lower level. If a subject
with the security class level L runs a command to uplevel tuples from
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