Anthony Klug
Abstract
A relational database models some part of the real world by a set of relations and a set of constraints. The constraints model properties of the stored information and must be maintained true at all times. For views defined over physically stored (base) relations, this is done by determining whether the view constraints are logical consequences of base relation constraints. A technique for determining such valid view constraints is presented in this paper. A generalization of the tableau chase is used. The idea of the method is to generate a tableau for the expression whose summary violates the test constraints in a “canonical” way. The chase then tries to remove this violation.
It is also shown how this method has applications to schema design. Relations not in normal form or having other deficiencies can be replaced by normal form projections without losing the ability to represent all constraint information.
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Index Terms
- Determining View dependencies using tableaux
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