EVALUATING RECURSIVE AND EXIVERSAL PREDICATES

摘要

Methods, systems, and apparatus, including computer programs encoded on computer storage media, for evaluating recursive predicates and exiversal predicates. One of the methods includes receiving an expression having an exiversal quantifier that specifies a condition x and a condition y. The expression is transformed into a second expression having multiple recursive calls, the second expression having a first non-negated term with a first recursive call in the condition y, and a second negated term with a second recursive call in the condition y. The second expression is evaluated using evaluation predicates that include a single delta predicate that replaces only the recursive call in the first non-negated term to identify data elements in the relation having at least one attribute satisfying the condition x and the condition y, and, for each attribute of the data element satisfying the condition x, the attribute also satisfies the condition y.

主权项

1. A computer-implemented method comprising:
receiving an expression having a programming language construct representing an exiversal predicate having an exiversal quantifier, wherein the construct specifies a condition x and a condition y, wherein the condition y includes a recursive call to the expression; transforming the expression into a second expression having multiple recursive calls, the second expression having a first non-negated term with a first recursive call in the condition y, and a second negated term with a second recursive call in the condition y; generating evaluation predicates including a single delta predicate that replaces only the recursive call in the first non-negated term; and evaluating the second expression using the generated evaluation predicates to identify data elements in the relation having at least one attribute satisfying the condition x and the condition y, and, for each attribute of the data element satisfying the condition x, the attribute also satisfies the condition y.