The semantics of an extended referential integrity for a multilevel secure relational data model

To prevent information leakage in multilevel secure data models, the concept of polyinstantiation was inevitably introduced. Unfortunately, when it comes to references through foreign key in multilevel relational data models, the polyinstantiation causes referential ambiguities. To resolve this problem, this paper proposes an extended referential integrity semantics for a multilevel relational data model, Multilevel Secure Referential Integrity Semantics (MLS-RIS). The MLS-RIS distinguishes foreign key into two types of references, i.e. value-based and entity-based reference. For each type, it defines the referential integrity to be held between two multilevel relations, and provides resolution rules for the referential ambiguities. In addition, the MLS-RIS specifies the semantics of referential actions of the SQL update operations so as to preserve the referential integrity. 2003 Elsevier B.V. All rights reserved.