Method for associating integrity maintenance constraints with data object classes in an object-oriented database

摘要

A technique is provided for the association of constraints with data object classes in an object-oriented database. Given a constraint comprising zero or more quantifiers followed by a quantifier- free boolean expression, a non-primitive reference expression is identified in the boolean expression. The constraint is then modified as follows. First, the primitive reference expression at the head of the identified non- primitive reference expression is replaced with a variable. Then a universal quantifier which quantifies the added variable over all data objects in the class comprising that primitive reference expression is added to the constraint. Finally, a disjunctive condition specifying that the added variable is not equal to the primitive reference expression is added to the boolean expression. The modified constraint may then be associated with the class comprising the aforesaid primitive reference expression. This modification may be performed repeatedly, for each of a number of non-primitive reference expressions. The boolean expression may comprise one or more function calls with implicit non-primitive references which may be identified. The modified constraint may then also be associated with classes based on these references. The modified constraint may be evaluated whenever an object in an associated class is updated. A modified constraint which has been associated with a given class may be further modified to improve evaluation efficiency.