Integrity Constraints Maintenance For Parallel Databases

This research work proposed a standard framework for maintaining integrity in parallel database systems. A model consisting of two main modules has been successfully implemented. This framework is flexible and can be extended easily as the framework is designed in a modular fashion where each module has a clear function, input and output and interacts easily with the other modules. A constraint verification method is proposed to check the consistency between the integrity constraints in the constraint base. The proposed method is based on the construction of Modal Records to determine if a newly defined constraint is not contradicting with an existing constraint set. A constraint simplification approach is proposed to simplify the integrity constraints in the constraint base. Deriving and checking a simplified version of the integrity constraint called integrity tests can gain efficiency. Efficient maintenance of integrity is a critical problem, since checking the validity of a large number of integrity constraints against a large database is crucial to the database systems. The derivation of these integrity tests is not trivial, adding to the cost of integrity maintenance. The strength of the proposed approach is that it combines the advantages of the substitution as well as the theorem proving technique in the previous work. The proposed approach is based on substitution and requires no resolution search. It requires no complex transition axioms to describe the update operations. The proposed method is considered as a general one since it derives complete integrity tests for first order constraints. In addition, it derives sufficient tests for key, referential and semantic integrity constraints. The complete and sufficient integrity tests can be applied before the update operation is performed. Moreover, it can be extended to deal with transition integrity constraints, which are excluded from the previous approaches. Transition integrity constraints are important since they give relationships between the two states that an update or transaction is required to obey. As the research interest is in parallel database system, this research has proposed a virtual rule partitioning method for maintaining database integrity by dynamically partition the table(s) to accommodate with parallel integrity subsystem. Therefore, there will be no fixed partitions specified during the design process, which result in time consuming for the system to locate the proper partition of data, for fulfilling the requirement of the integrity test. The presented method is benefited from the direct access method because the tuples in each partition are indexed according to the test attribute during the execution of the integrity test. The test attribute is the attribute of the generated test that is substituted by the submitted update operation.

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