Fast methods for testing quantified relational calculus assertions

  • Authors:

  • Philip A. Bernstein;Barbara T. Blaustein

  • Affiliations:

  • Harvard University, Cambridge, MA;Computer Corporation of America, Cambridge, MA

  • Venue:
  • SIGMOD '82 Proceedings of the 1982 ACM SIGMOD international conference on Management of data
  • Year:
  • 1982

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Abstract

Semantic integrity assertions are predicates that define consistent states. A database system enforces assertions by ensuring that consistency is maintained as the database is updated.Most research on the efficient enforcement of assertions has concentrated on assertion simplification algorithms --- algorithms that produce simplified assertions that can be evaluated before the update is executed. This paper describes a strategy for further improving the efficiency of assertion enforcement.We develop an efficient algorithm for evaluating an assertion produced by an assertion simplification algorithm. We characterize a class of assertions that can be evaluated using a simple two-step procedure. The first step defines and evaluates simple selection queries on each relation. The second step applies set emptiness tests to the results of these selections. We also show how these techniques may be used to improve the efficiency of evaluating assertions outside our class.