Database Reference
In-Depth Information
• Step 2: make a logical view over the stored single security level
relations by performing join between vertical single security
class level relations and union between horizontal single-level
relations.
• Step 3: get all tuples from the logical view that have security
levels below or equal to the security class level of the subject
that runs the selection operation.
Figure 3.1 illustrates the flow chart for the selection operation in the
SeaView model.
3.2.2 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
]
Get user class
Get logical view for stored single-level
relations by union and join operation
Get rst row from logical view
No
Get next row
Row class <= user class
Ye s
Display Row
End
Figure 3.1
Flow chart for selection operation in the SeaView model.
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