ELS-programs and the efficient evaluation of non-stratified programs by transformation to ELS

Abstract

We give a simple transformation from normal programs with no stratification (local, weak, modular, etc.) into a subclass of the locally stratified programs, called Explicitly Locally Stratified (ELS) programs, for which there are efficient evaluation techniques. One set of predicates are generated for the true tuples and a different set of predicate are generated for the true and undefined tuples. A similar transformation is given that incorporates a magic sets like transformation. Previous approaches to magic sets transformations of unstratified programs either restricted the class of sips used or generated a program that required special treatment of the magic sets predicates. Our transfor..