Database Reference
In-Depth Information
level L runs a command to delete tuples from MLS relation R: for all
t
∈ R, if
t
satisfies P and Pl is equal to the security class level of the
user L, the delete operation is implemented as follows [35]:
• Step 1: get the security level of the subject that runs the delete
operation.
• Step 2: if Sl (Xview(Tuple Class)) is NULL, the tuple will be
deleted.
• Step 3: if Sl (Xview(Tuple Class)) is not NULL, unverify the
tuple for the current user and set the flag for higher level users.
• Step 4: unverify all tuples with the same primary key and its
security level as the deleted tuple having Ib(tc) = l (belief: false).
Figure 3.21 illustrates the flow chart for the delete operation in the
belief-consistent model.
Get user class L(user)
Set i = 1
Pl(ti
i
[TC]) = L(user) and
Sl(Xview(ti
i
[TC])) = Null
Ye s
No
Unverify t
i
for current user
Detele ti
i
Set �ag for higher level users
Set j = 1
i = i + 1
j = j + l
No
t
j
[PK, C
PK
] = t
i
[PK, C
PK
] and
Ib(t
j
[TC]) = 1
Ye s
Unverify t
j
for current user
End
Figure 3.21
Flow chart for delete operation in the belief-consistent model.
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