Polyinstantiation

1. 1 Polyinstantiation

2. 2 Polyinstantiation Definition and need for polyinstantiation Sea View model Jajodia – Sandhu model

3. 3 Definition and need for polyinstantiation Polyinstantiation is a database technique that allows the database to contain multiple instances of the same data but with different classifications Polyinstantiation occurs because of mandatory policy In relational DBMS it is possible to have different tuples with the same key but with different classifications

4. 4 Definition and need for polyinstantiation Polyinstantiation can affect relations, tuples and data elements Polyinstantiation arises because subjects with different classes are allowed to operate on the same relations Polyinstantiated relations are relations with different access classes Polyinstantiated tuples (also called entity polyinstantiation) are tuples with the same primary key but with different access classes associated to the primary keys

5. 5 Definition and need for polyinstantiation Polyinstantiated elements (also called attribute polyinstantiation) are elements of an attribute which have different access classes but are associated with the same primary key and key class Polyinstantiation occurs as one of: Visible polyinstantiation Invisible polyinstantiation

6. 6 Definition and need for polyinstantiation Visible polyinstantiation occurs when a higher user attempts to insert data in a field that already contains low data. The high data is entered as a new tuple. Invisible polyinstantiation occurs when a low user attempts to insert data in a field that already contains high data. The low data is entered as a new tuple.

7. 7 Example of polyinstantiated relation