Database Reference
In-Depth Information
6.3.2 Polyinstantiation Integrity
In polyinstantiation integrity (PI), a multilevel relational database
instance
r
satisfies the polyinstantiation integrity if the following
requirement exists [78]:
For 1 ≤
i
≤
n:
A
1
,
TC
→
C
i
;
and
A
1
,
C
1
,
C
i
→
A
i
;
This property ensures that the primary key attribute
A
1
, in conjunction
with the security classification level attributes
C
1
and
C
i
,
functionally
determines the value of the
A
i
attribute.
6.3.3 Data-Borrow Integrity
In data-borrow integrity (DBI), a multilevel relational database instance
r
satisfies the data borrow if the following requirement exists [79]:
For 1 ≤
i
≤
n,
all the nonprimary key attributes in tuple
t
∈
r
that
have data encrypted by key according to security classification levels
lower than the tuple classification level, there exists polyinstantiated
tuple
t
′ that has
t
′[
A
1
] =
t
[
A
1
] ∧
t
′[
TC
] =
t
′[
c
i
] =
t
[
c
i
] ∧
t
′[
A
i
] =
t
[
A
i
].
6.3.4 Foreign Key Integrity
In foreign key integrity (FKI), let
FK
be a foreign key of the referenc-
ing relation
R
. A multilevel relational database instance
r
satisfies the
foreign key if the following requirement exists [79]:
For each tuple
t
∈
r:
(∀
A
i
∈
FK
),
t
[
A
i
] ≠ null
and
A
i
,
A
i
∈
FK
⇒
t
[
C
i
] =
t
[
C
i
]
The first requirement of this property ensures that no foreign key
attribute in the referencing relation has a null data value. The second
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