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  - Fandinno, Jorge
A1  - Laferriere, Francois
A1  - Romero, Javier
A1  - Schaub, Torsten H.
A1  - Son, Tran Cao
T1  - Planning with incomplete information in quantified answer set programming
JF  - Theory and practice of logic programming
N2  - We present a general approach to planning with incomplete information in Answer Set Programming (ASP). More precisely, we consider the problems of conformant and conditional planning with sensing actions and assumptions. We represent planning problems using a simple formalism where logic programs describe the transition function between states, the initial states and the goal states. For solving planning problems, we use Quantified Answer Set Programming (QASP), an extension of ASP with existential and universal quantifiers over atoms that is analogous to Quantified Boolean Formulas (QBFs). We define the language of quantified logic programs and use it to represent the solutions different variants of conformant and conditional planning. On the practical side, we present a translation-based QASP solver that converts quantified logic programs into QBFs and then executes a QBF solver, and we evaluate experimentally the approach on conformant and conditional planning benchmarks.
KW  - answer set programming
KW  - planning
KW  - quantified logics
Y1  - 2021
U6  - https://doi.org/10.1017/S1471068421000259
SN  - 1471-0684
SN  - 1475-3081
VL  - 21
IS  - 5
SP  - 663
EP  - 679
PB  - Cambridge University Press
CY  - Cambridge
ER  - 
TY  - JOUR
A1  - Cabalar, Pedro
A1  - Fandinno, Jorge
A1  - Lierler, Yuliya
T1  - Modular Answer Set Programming as a formal specification language
JF  - Theory and practice of logic programming
N2  - In this paper, we study the problem of formal verification for Answer Set Programming (ASP), namely, obtaining aformal proofshowing that the answer sets of a given (non-ground) logic programPcorrectly correspond to the solutions to the problem encoded byP, regardless of the problem instance. To this aim, we use a formal specification language based on ASP modules, so that each module can be proved to capture some informal aspect of the problem in an isolated way. This specification language relies on a novel definition of (possibly nested, first order)program modulesthat may incorporate local hidden atoms at different levels. Then,verifyingthe logic programPamounts to prove some kind of equivalence betweenPand its modular specification.
KW  - Answer Set Programming
KW  - formal specification
KW  - formal verification
KW  - modular logic programs
Y1  - 2020
U6  - https://doi.org/10.1017/S1471068420000265
SN  - 1471-0684
SN  - 1475-3081
VL  - 20
IS  - 5
SP  - 767
EP  - 782
PB  - Cambridge University 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  - Aguado, Felicidad
A1  - Cabalar, Pedro
A1  - Fandinno, Jorge
A1  - Pearce, David
A1  - Perez, Gilberto
A1  - Vidal, Concepcion
T1  - Forgetting auxiliary atoms in forks
JF  - Artificial intelligence
N2  - In this work we tackle the problem of checking strong equivalence of logic programs that may contain local auxiliary atoms, to be removed from their stable models and to be forbidden in any external context. We call this property projective strong equivalence (PSE). It has been recently proved that not any logic program containing auxiliary atoms can be reformulated, under PSE, as another logic program or formula without them – this is known as strongly persistent forgetting. In this paper, we introduce a conservative extension of Equilibrium Logic and its monotonic basis, the logic of Here-and-There, in which we deal with a new connective ‘|’ we call fork. We provide a semantic characterisation of PSE for forks and use it to show that, in this extension, it is always possible to forget auxiliary atoms under strong persistence. We further define when the obtained fork is representable as a regular formula.
KW  - Answer set programming
KW  - Non-monotonic reasoning
KW  - Equilibrium logic
KW  - Denotational semantics
KW  - Forgetting
KW  - Strong equivalence
Y1  - 2019
U6  - https://doi.org/10.1016/j.artint.2019.07.005
SN  - 0004-3702
SN  - 1872-7921
VL  - 275
SP  - 575
EP  - 601
PB  - Elsevier
CY  - Amsterdam
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  -