Lazy-Grounding for Answer Set Programs with External Source Access

Eiter, Thomas; Kaminski, Tobias; Weinzierl, Antonius

doi:10.24963/ijcai.2017/141

Cited by 9 publications

(8 citation statements)

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“…These solvers all have in common that they process only normal rules, i.e., they allow for only ordinary literals in rule bodies and no disjunction in heads, and in particular, they do not support aggregates. Recent developments around Alpha are on exploiting justifications (Bogaerts and Weinzierl 2018) as well as its use in evaluating external atoms (Eiter, Kaminski, and Weinzierl 2017). Furthermore, Alpha is the only lazy-grounding ASP system with efficient techniques for search (CDNL), hence it was taken as basis for this work.…”

Section: Discussionmentioning

confidence: 99%

Enhancing Lazy Grounding with Lazy Normalization in Answer-Set Programming

Bomanson

Janhunen

Weinzierl

2019

AAAI

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Answer-Set Programming (ASP) is an expressive rule-based knowledge-representation formalism. Lazy grounding is a solving technique that avoids the well-known grounding bottleneck of traditional ASP evaluation but is restricted to normal rules, severely limiting its expressive power. In this work, we introduce a framework to handle aggregates by normalizing them on demand during lazy grounding, hence relieving the restrictions of lazy grounding significantly. We term our approach as lazy normalization and demonstrate its feasibility for different types of aggregates. Asymptotic behavior is analyzed and correctness of the presented lazy normalizations is shown. Benchmark results indicate that lazy normalization can bring up-to exponential gains in space and time as well as enable ASP to be used in new application areas.

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Section: Discussionmentioning

confidence: 99%

Enhancing Lazy Grounding with Lazy Normalization in Answer-Set Programming

Bomanson

Janhunen

Weinzierl

2019

AAAI

Self Cite

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“…Another intriguing issue would be to analyze the relationships between the notions of safety of (Eiter et al 2013) and the notions of boundedness used by termination criteria.…”

Section: Discussionmentioning

confidence: 99%

“…To this end, an interesting approach would be to plug termination criteria in the generic framework proposed in (Eiter et al 2013) and study their combination in such a framework. Another intriguing issue would be to analyze the relationships between the notions of safety of (Eiter et al 2013) and the notions of boundedness used by termination criteria.…”

Section: Discussionmentioning

confidence: 99%

Using linear constraints for logic program termination analysis

Greco¹,

Molinaro²,

Trubitsyna³

2016

Theory and Practice of Logic Programming

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It is widely acknowledged that function symbols are an important feature in answer set programming, as they make modeling easier, increase the expressive power, and allow us to deal with infinite domains. The main issue with their introduction is that the evaluation of a program might not terminate and checking whether it terminates or not is undecidable. To cope with this problem, several classes of logic programs have been proposed where the use of function symbols is restricted but the program evaluation termination is guaranteed. Despite the significant body of work in this area, current approaches do not include many simple practical programs whose evaluation terminates. In this paper, we present the novel classes of rule-bounded and cycle-bounded programs, which overcome different limitations of current approaches by performing a more global analysis of how terms are propagated from the body to the head of rules. Results on the correctness, the complexity, and the expressivity of the proposed approach are provided. Under consideration in Theory and Practice of Logic Programming (TPLP).

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“…A corresponding ASP encoding for the non-probabilistic case for Card exists [Sch15,Simpl], however it shows prohibitively bad performance. The termination proofs we do are related to the notion of Liberal Safety in HEX programs [EFKR13], however Liberal Safety requires either specific acyclicity conditions (which are absent in our encodings), or conditions on finiteness of the domain of certain attributes of the external atom (that our Skolemization atoms do not fulfill). Hence we had to prove termination without using Liberal Safety.…”

Section: Related Workmentioning

confidence: 99%

Modeling Variations of First-Order Horn Abduction in Answer Set Programming

Schüller

2016

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We study abduction in First Order Horn logic theories where all atoms can be abduced and we are looking for preferred solutions with respect to three objective functions: cardinality minimality, coherence, and weighted abduction. We represent this reasoning problem in Answer Set Programming (ASP), in order to obtain a flexible framework for experimenting with global constraints and objective functions, and to test the boundaries of what is possible with ASP. Realizing this problem in ASP is challenging as it requires value invention and equivalence between certain constants, because the Unique Names Assumption does not hold in general. To permit reasoning in cyclic theories, we formally describe fine-grained variations of limiting Skolemization. We identify term equivalence as a main instantiation bottleneck, and improve the efficiency of our approach with on-demand constraints that were used to eliminate the same bottleneck in state-of-the-art solvers. We evaluate our approach experimentally on the ACCEL benchmark for plan recognition in Natural Language Understanding. Our encodings are publicly available, modular, and our approach is more efficient than state-of-the-art solvers on the ACCEL benchmark. * This work is a significant extension of [Sch15]; major additions are preference relations Coh and Wa, revised encodings, increase performance, on-demand constraints, and flexible value invention. This work has been supported by Scientific and Technological Research Council of Turkey (TUBITAK) Grant 114E777. This document is a preprint of [Sch16] with minor formatting corrections.

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Lazy-Grounding for Answer Set Programs with External Source Access

Cited by 9 publications

References 10 publications

Enhancing Lazy Grounding with Lazy Normalization in Answer-Set Programming

Enhancing Lazy Grounding with Lazy Normalization in Answer-Set Programming

Using linear constraints for logic program termination analysis

Modeling Variations of First-Order Horn Abduction in Answer Set Programming

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