Weakest and Incremental Preconditions for Constraint Checking

Constraint checking plays a critical role in maintaining validity of database semantics Straightforward verification of the constraintsafter each transaction is very expensive An alternative approachis to derive a simplified condition from the involvedtransaction and constraint, which can be checked before theupdate to ensure the constraint holds after the update A method based on weakest and incremental precondition is givenfor efficiently calculating necessary and sufficient conditionsfor such test Sufficient conditions are generally simpler to evaluate with the assumption that the constraint holds in currentdatabase state This method deals with more general constraintsand transactions than other approaches do and the derivation oftest conditions is more effective