TY  - JOUR
A1  - Cabalar, Pedro
A1  - Dieguez, Martin
A1  - Schaub, Torsten H.
A1  - Schuhmann, Anna
T1  - Towards metric temporal answer set programming
JF  - Theory and practice of logic programming
N2  - We elaborate upon the theoretical foundations of a metric temporal extension of Answer Set Programming. In analogy to previous extensions of ASP with constructs from Linear Temporal and Dynamic Logic, we accomplish this in the setting of the logic of Here-and-There and its non-monotonic extension, called Equilibrium Logic. More precisely, we develop our logic on the same semantic underpinnings as its predecessors and thus use a simple time domain of bounded time steps. This allows us to compare all variants in a uniform framework and ultimately combine them in a common implementation.
Y1  - 2020
U6  - https://doi.org/10.1017/S1471068420000307
SN  - 1471-0684
SN  - 1475-3081
VL  - 20
IS  - 5
SP  - 783
EP  - 798
PB  - Cambridge Univ. Press
CY  - Cambridge [u.a.]
ER  - 
TY  - JOUR
A1  - Fandinno, Jorge
A1  - Lifschitz, Vladimir
A1  - Lühne, Patrick
A1  - Schaub, Torsten H.
T1  - Verifying tight logic programs with Anthem and Vampire
JF  - Theory and practice of logic programming
N2  - This paper continues the line of research aimed at investigating the relationship between logic programs and first-order theories. We extend the definition of program completion to programs with input and output in a subset of the input language of the ASP grounder gringo, study the relationship between stable models and completion in this context, and describe preliminary experiments with the use of two software tools, anthem and vampire, for verifying the correctness of programs with input and output. Proofs of theorems are based on a lemma that relates the semantics of programs studied in this paper to stable models of first-order formulas.
Y1  - 2020
U6  - https://doi.org/10.1017/S1471068420000344
SN  - 1471-0684
SN  - 1475-3081
VL  - 20
IS  - 5
SP  - 735
EP  - 750
PB  - Cambridge Univ. Press
CY  - Cambridge [u.a.]
ER  - 
TY  - JOUR
A1  - Cabalar, Pedro
A1  - Fandinno, Jorge
A1  - Garea, Javier
A1  - Romero, Javier
A1  - Schaub, Torsten H.
T1  - Eclingo
BT  - a solver for epistemic logic programs
JF  - Theory and practice of logic programming
N2  - We describe eclingo, a solver for epistemic logic programs under Gelfond 1991 semantics built upon the Answer Set Programming system clingo. The input language of eclingo uses the syntax extension capabilities of clingo to define subjective literals that, as usual in epistemic logic programs, allow for checking the truth of a regular literal in all or in some of the answer sets of a program. The eclingo solving process follows a guess and check strategy. It first generates potential truth values for subjective literals and, in a second step, it checks the obtained result with respect to the cautious and brave consequences of the program. This process is implemented using the multi-shot functionalities of clingo. We have also implemented some optimisations, aiming at reducing the search space and, therefore, increasing eclingo 's efficiency in some scenarios. Finally, we compare the efficiency of eclingo with two state-of-the-art solvers for epistemic logic programs on a pair of benchmark scenarios and show that eclingo generally outperforms their obtained results.
KW  - Answer Set Programming
KW  - Epistemic Logic Programs
KW  - Non-Monotonic
KW  - Reasoning
KW  - Conformant Planning
Y1  - 2020
U6  - https://doi.org/10.1017/S1471068420000228
SN  - 1471-0684
SN  - 1475-3081
VL  - 20
IS  - 6
SP  - 834
EP  - 847
PB  - Cambridge Univ. Press
CY  - New York
ER  - 
TY  - JOUR
A1  - Cabalar, Pedro
A1  - Fandinno, Jorge
A1  - Schaub, Torsten H.
A1  - Schellhorn, Sebastian
T1  - Gelfond-Zhang aggregates as propositional formulas
JF  - Artificial intelligence
N2  - Answer Set Programming (ASP) has become a popular and widespread paradigm for practical Knowledge Representation thanks to its expressiveness and the available enhancements of its input language. One of such enhancements is the use of aggregates, for which different semantic proposals have been made. In this paper, we show that any ASP aggregate interpreted under Gelfond and Zhang's (GZ) semantics can be replaced (under strong equivalence) by a propositional formula. Restricted to the original GZ syntax, the resulting formula is reducible to a disjunction of conjunctions of literals but the formulation is still applicable even when the syntax is extended to allow for arbitrary formulas (including nested aggregates) in the condition. Once GZ-aggregates are represented as formulas, we establish a formal comparison (in terms of the logic of Here-and-There) to Ferraris' (F) aggregates, which are defined by a different formula translation involving nested implications. In particular, we prove that if we replace an F-aggregate by a GZ-aggregate in a rule head, we do not lose answer sets (although more can be gained). This extends the previously known result that the opposite happens in rule bodies, i.e., replacing a GZ-aggregate by an F-aggregate in the body may yield more answer sets. Finally, we characterize a class of aggregates for which GZ- and F-semantics coincide.
KW  - Aggregates
KW  - Answer Set Programming
Y1  - 2019
U6  - https://doi.org/10.1016/j.artint.2018.10.007
SN  - 0004-3702
SN  - 1872-7921
VL  - 274
SP  - 26
EP  - 43
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Dimopoulos, Yannis
A1  - Gebser, Martin
A1  - Lühne, Patrick
A1  - Romero Davila, Javier
A1  - Schaub, Torsten H.
T1  - plasp 3
BT  - Towards Effective ASP Planning
JF  - Theory and practice of logic programming
N2  - We describe the new version of the Planning Domain Definition Language (PDDL)-to-Answer Set Programming (ASP) translator plasp. First, it widens the range of accepted PDDL features. Second, it contains novel planning encodings, some inspired by Satisfiability Testing (SAT) planning and others exploiting ASP features such as well-foundedness. All of them are designed for handling multivalued fluents in order to capture both PDDL as well as SAS planning formats. Third, enabled by multishot ASP solving, it offers advanced planning algorithms also borrowed from SAT planning. As a result, plasp provides us with an ASP-based framework for studying a variety of planning techniques in a uniform setting. Finally, we demonstrate in an empirical analysis that these techniques have a significant impact on the performance of ASP planning.
KW  - knowledge representation and nonmonotonic reasoning
KW  - technical notes and rapid communications
KW  - answer set programming
KW  - automated planning
KW  - action and change
Y1  - 2019
U6  - https://doi.org/10.1017/S1471068418000583
SN  - 1471-0684
SN  - 1475-3081
VL  - 19
IS  - 3
SP  - 477
EP  - 504
PB  - Cambridge Univ. Press
CY  - New York
ER  - 
TY  - GEN
A1  - Cabalar, Pedro
A1  - Fandinno, Jorge
A1  - Schaub, Torsten H.
A1  - Schellhorn, Sebastian
T1  - Lower Bound Founded Logic of Here-and-There
T2  - Logics in Artificial Intelligence
N2  - A distinguishing feature of Answer Set Programming is that all atoms belonging to a stable model must be founded. That is, an atom must not only be true but provably true. This can be made precise by means of the constructive logic of Here-and-There, whose equilibrium models correspond to stable models. One way of looking at foundedness is to regard Boolean truth values as ordered by letting true be greater than false. Then, each Boolean variable takes the smallest truth value that can be proven for it. This idea was generalized by Aziz to ordered domains and applied to constraint satisfaction problems. As before, the idea is that a, say integer, variable gets only assigned to the smallest integer that can be justified. In this paper, we present a logical reconstruction of Aziz’ idea in the setting of the logic of Here-and-There. More precisely, we start by defining the logic of Here-and-There with lower bound founded variables along with its equilibrium models and elaborate upon its formal properties. Finally, we compare our approach with related ones and sketch future work.
Y1  - 2019
SN  - 978-3-030-19570-0
SN  - 978-3-030-19569-4
U6  - https://doi.org/10.1007/978-3-030-19570-0_34
SN  - 0302-9743
SN  - 1611-3349
VL  - 11468
SP  - 509
EP  - 525
PB  - Springer
CY  - Cham
ER  - 
TY  - JOUR
A1  - Frioux, Clémence
A1  - Schaub, Torsten H.
A1  - Schellhorn, Sebastian
A1  - Siegel, Anne
A1  - Wanko, Philipp
T1  - Hybrid metabolic network completion
JF  - Theory and practice of logic programming
N2  - Metabolic networks play a crucial role in biology since they capture all chemical reactions in an organism. While there are networks of high quality for many model organisms, networks for less studied organisms are often of poor quality and suffer from incompleteness. To this end, we introduced in previous work an answer set programming (ASP)-based approach to metabolic network completion. Although this qualitative approach allows for restoring moderately degraded networks, it fails to restore highly degraded ones. This is because it ignores quantitative constraints capturing reaction rates. To address this problem, we propose a hybrid approach to metabolic network completion that integrates our qualitative ASP approach with quantitative means for capturing reaction rates. We begin by formally reconciling existing stoichiometric and topological approaches to network completion in a unified formalism. With it, we develop a hybrid ASP encoding and rely upon the theory reasoning capacities of the ASP system dingo for solving the resulting logic program with linear constraints over reals. We empirically evaluate our approach by means of the metabolic network of Escherichia coli. Our analysis shows that our novel approach yields greatly superior results than obtainable from purely qualitative or quantitative approaches.
KW  - answer set programming
KW  - metabolic network
KW  - gap-filling
KW  - linear programming
KW  - hybrid solving
KW  - bioinformatics
Y1  - 2018
U6  - https://doi.org/10.1017/S1471068418000455
SN  - 1471-0684
SN  - 1475-3081
VL  - 19
IS  - 1
SP  - 83
EP  - 108
PB  - Cambridge University Press
CY  - New York
ER  - 
TY  - JOUR
A1  - Schaub, Torsten H.
A1  - Woltran, Stefan
T1  - Answer set programming unleashed!
JF  - Künstliche Intelligenz
N2  - Answer Set Programming faces an increasing popularity for problem solving in various domains. While its modeling language allows us to express many complex problems in an easy way, its solving technology enables their effective resolution. In what follows, we detail some of the key factors of its success. Answer Set Programming [ASP; Brewka et al. Commun ACM 54(12):92–103, (2011)] is seeing a rapid proliferation in academia and industry due to its easy and flexible way to model and solve knowledge-intense combinatorial (optimization) problems. To this end, ASP offers a high-level modeling language paired with high-performance solving technology. As a result, ASP systems provide out-off-the-box, general-purpose search engines that allow for enumerating (optimal) solutions. They are represented as answer sets, each being a set of atoms representing a solution. The declarative approach of ASP allows a user to concentrate on a problem’s specification rather than the computational means to solve it. This makes ASP a prime candidate for rapid prototyping and an attractive tool for teaching key AI techniques since complex problems can be expressed in a succinct and elaboration tolerant way. This is eased by the tuning of ASP’s modeling language to knowledge representation and reasoning (KRR). The resulting impact is nicely reflected by a growing range of successful applications of ASP [Erdem et al. AI Mag 37(3):53–68, 2016; Falkner et al. Industrial applications of answer set programming. K++nstliche Intelligenz (2018)]
Y1  - 2018
U6  - https://doi.org/10.1007/s13218-018-0550-z
SN  - 0933-1875
SN  - 1610-1987
VL  - 32
IS  - 2-3
SP  - 105
EP  - 108
PB  - Springer
CY  - Heidelberg
ER  - 
TY  - GEN
A1  - Schaub, Torsten H.
A1  - Woltran, Stefan
T1  - Special issue on answer set programming
T2  - Künstliche Intelligenz
Y1  - 2018
U6  - https://doi.org/10.1007/s13218-018-0554-8
SN  - 0933-1875
SN  - 1610-1987
VL  - 32
IS  - 2-3
SP  - 101
EP  - 103
PB  - Springer
CY  - Heidelberg
ER  - 
TY  - GEN
A1  - Schäpers, Björn
A1  - Niemueller, Tim
A1  - Lakemeyer, Gerhard
A1  - Gebser, Martin
A1  - Schaub, Torsten H.
T1  - ASP-Based Time-Bounded Planning for Logistics Robots
T2  - Twenty-Eighth International Conference on Automated Planning and Scheduling (ICAPS 2018)
N2  - Manufacturing industries are undergoing a major paradigm shift towards more autonomy. Automated planning and scheduling then becomes a necessity. The Planning and Execution Competition for Logistics Robots in Simulation held at ICAPS is based on this scenario and provides an interesting testbed. However, the posed problem is challenging as also demonstrated by the somewhat weak results in 2017. The domain requires temporal reasoning and dealing with uncertainty. We propose a novel planning system based on Answer Set Programming and the Clingo solver to tackle these problems and incentivize robot cooperation. Our results show a significant performance improvement, both, in terms of lowering computational requirements and better game metrics.
Y1  - 2018
SN  - 2334-0835
SN  - 2334-0843
SP  - 509
EP  - 517
PB  - ASSOC Association for the Advancement of Artificial Intelligence
CY  - Palo Alto
ER  -