Formal Analysis for Encryption- Based Multilevel Model for DBMS - Multilevel Security for Relational Databases - page 119

requirement ensures that all the foreign key attributes FK should have
the same security classification level in the tuple t ∈ r.

6.3.5 Referential Integrity

In referential integrity (RI), suppose that FK1 is defined for a foreign
key in the referencing relation R 1 that has a primary key AK 1 . Suppose
that R 2 is defined for the referenced relation that has a primary key
AK 2 [80]. Multilevel relational database instances r 1 , r 2 satisfy the
referential integrity if the following requirement exists:
For all

t 11 ∈ r 1

such that

t 11 [ FK 1 ] ≠ null,

there exists

t 21 ∈ r 2

such that

tFKt [ ] = [ AK ] ∧ tTCt [] = [] [ TC ∧ tC ] ≥ tC [ ]

,

11 1 21 2 11 21 11 FK 21 AK 1 2

and for all

t 11 , t 12 ∈ r 1

and

t 21 , t 22 ∈ r 2 ,

if

tAKt [ ] = [ AK ] ∧ tTCt [] = [] [] TC ∧ tTCt = [] TC 11 1 12 1 11 21 12 22

= tC [ ] = tC [ ] ∧ tFKt [ ] = [ AK ]

11 FK 12 FK 11 1 21 2 1 1

= t [ K ],then[ t AK ] = t [ K ].

22 2 21 2 22 2

6.4 Manipulation

This section presents the data manipulation statements for the
encryption-based multilevel database model.