A new polyinstantiation integrity constraint for multilevel relations

Abstract
We propose a new polyinstantiation integrity constraintfor multilevel relations based on the intuitiveidea that every entity in a relation can have at mostone tuple for every access class. We discuss the consequencesof this property and some of its variations.1 INTRODUCTIONIn multilevel environments it is inherent that userswith different clearances see different sets of facts.This inevitably results in polyinstantiation, i.e., thesimultaneous existence of data objects, attributes or...

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