Foundations of logic programming; (2nd extended ed.)
Foundations of logic programming; (2nd extended ed.)
Handbook of theoretical computer science (vol. B)
Proceedings of the eleventh international conference on Logic programming
Nested expressions in logic programs
Annals of Mathematics and Artificial Intelligence
Perfect Model Checking via Unfold/Fold Transformations
CL '00 Proceedings of the First International Conference on Computational Logic
Strong equivalence made easy: nested expressions and weight constraints
Theory and Practice of Logic Programming
On inductive proofs by extended unfold/fold transformation rules
LOPSTR'10 Proceedings of the 20th international conference on Logic-based program synthesis and transformation
On inductive and coinductive proofs via unfold/fold transformations
LOPSTR'09 Proceedings of the 19th international conference on Logic-Based Program Synthesis and Transformation
Using real relaxations during program specialization
LOPSTR'11 Proceedings of the 21st international conference on Logic-Based Program Synthesis and Transformation
Improving Reachability Analysis of Infinite State Systems by Specialization
Fundamenta Informaticae - Concurrency Specification and Programming (CS&P)
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We study negative unfolding for logic programs from a viewpoint of preservation of the answer set semantics. To this end, we consider negative unfolding in terms of nested expressions by Lifschitz et al., and regard it as a combination of the replacement of a literal by its definition (called "pre-negative unfolding") and double negation elimination. We give sufficient conditions for preserving the answer set semantics. We then consider a framework for unfold/fold transformation of locally stratified programs, which, besides negative unfolding, contains replacement rules, allowing a more general form than those proposed by Pettorossi and Proietti. A new folding condition for the correctness proof is identified, which is not required either for definite or stratified programs, but becomes necessary only in case of locally stratified programs. An extension of the framework beyond the class of locally stratified programs is also discussed.