Database Reference
In-Depth Information
8.5 Insert Operation Procedure of the IBMSM
The SQL-like command for the insert operation has the following
form:
INSERT
INTO R [A
i
]
*
VALUES [a
i
]
*
The insertion operation is implemented as follows:
Step 1: get the classification level of the user that executes the
insert operation L(User).
Step 2: get the class views that belong to this user.
Step 3: 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; otherwise, the value of
this attribute will be null.
Step 4: insert the new instance with properties of the attributes'
values and the class level of the user into the multilevel relation.
Figure 8.3 illustrates the INSERT operation procedure in IBMSM.
8.6 The Update Operation Procedure of the IBMSM
The SQL-like command for the update operation has the following
form:
UPDATE R
SET A
i
= a
i
,[A
i
=a
i
]*
WHERE P
The update operation is implemented as follows:
Step 1: get the classification level of the user that executes the
update operation L(User).
Step 2: get the class views that belong to this user.
Step 3: get all the instance views that belong to the class views of
the user and satisfy the update condition P.
Step 4: for each instance, in the instance views, update the prop-
erty that has class level equal to the class level of the user.
Figure 8.4 illustrates the UPDATE operation procedure in IBMSM.
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