Research On Multilevel Secure Data Model And Transaction Processing

As a result of deeply application of information technology in national economy and national defense, information security become extremely important for national development and security. As a basic software of MIS, DBMS is at a critical position of information security stratety. Moreover, The event that Army of United States destroyed Iraqian air-defense system via computer virus in war of 1991 illustrates: using foreign products in important fields will introduce muderous loopholes to national security. So it means significant in national strategy for exploiting theory and application of secure database.On the basis of existing data models, this tutorial presents an improved multilevel secure relational data model-MLSR, which clarifies the data-based semantics by extending the classification of polyinstantiation from two to three and solves the data redundance coming up with polyinstantiation by dividing relational schema into view schema and storage schema. For key loophole, MLSR refers to the idea of System Defined Entity Identifier of BCMLS, then improves it and turns it from theory to realization.On the basis of existing extended transaction models, this tutorial presents a new transaction processing mechanism. By using a kind of improved nested transaction model, the mechanism not only reduces probability of transaction starvation, but also obtains the ability of supporting multilevel transaction processing. By using the improved 2PL lock protocol, the mechanism makes the read opertaion of low-level data not interfereing the write operation towards the same data which guarantees the security of single-level transaction processing, and guarantees the serializability of mechanism. After that, the tutorial presents the realization of this mechanism.