Comparative study of polyinstantiation models in MLS database

Polyinstantiabtion provides the ability to create more versions of single information. It is used to prevent inference attacks. This paper explains the use of polyinstantiation in relational databases with multilevel security. Also, shows how polyinstantiation can be occurred and what types of polyinstantiation. The basic concepts of multilevel security database models are described and issues regarding the MLS such as semantics, decomposition and recovery algorithms are considered. A comparison of well-known multilevel security models (SeaView, Jajodia-Sandhu, Smith-Winslett, MLR, and Belief-Consistent Model) is given. The main problems such as semantic ambiguity caused by the lack of semantics or incomplete semantic definitions, proliferation problem, Restriction of the scope of an update and disbelief in a tuple are discussed.