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El autor Joaquín Arias ha publicado 5 artículo(s):

1 - Description and Evaluation of a Generic Design to Integrate CLP and Tabled Execution (Trabajo de alto nivel)

Logic programming systems with tabling and constraints (TCLP, tabled constraint logic
programming) have been shown to be more expressive and in some cases more efficient
than those featuring only either tabling or constraints. Previous implementations of TCLP
systems which use entailment to determine call / answer subsumption did not provide a
simple, uniform, and well-documented interface to facilitate the integration of additional
constraint solvers in existing tabling systems, which would increase the application range of
TCLP. We present the design and an experimental evaluation of Mod TCLP, a framework
which eases this integration. Mod TCLP views the constraints solver as a client of the tabling
system. The tabling system is generic w.r.t. the constraint solver and only requires a clear,
small interface from the latter. We validate our design by integrating four constraint solvers:
a re-engineered version of a previously existing constraint solver for difference constraints,
written in C; the standard versions of Holzbauer’s CLP(Q) and CLP(R), written in Prolog;
and a new constraint solver for equations over finite lattices. We evaluate the performance
of our framework in several benchmarks using the aforementioned constraint solvers. All
the development work and evaluation was done in Ciao Prolog.

Autores: Joaquín Arias / Manuel Carro / 
Palabras Clave: constraints - Implementation - Interface - Prolog - Tabling

2 - Constraint Answer Set Programming without Grounding (Trabajo ya publicado)

Extending ASP with constraints (CASP) enhances its expressiveness and performance. This extension is not straightforward as the grounding phase, present in most ASP systems, removes variables and the links among them, and also causes a combinatorial explosion in the size of the program. This has led CASP systems to devise several methods to overcome this issue: restricting the constraint domains (e.g., discrete instead of dense), where constraints can appear, or the type (or number) of models that can be returned. In this paper we propose to incorporate constraints into s(ASP), a goal-directed, top-down execution model which implements ASP while retaining logical variables both during execution and in the answer sets. The resulting model, s(CASP), can constrain variables that (as in CLP) are kept during the execution and in the answer sets. s(CASP) inherits and generalizes the execution model of s(ASP) while parameterizing the constraint solver. We describe this novel execution model and show, through several examples, the enhanced expressiveness of s(CASP) w.r.t. ASP, CLP, and other ASP systems with constraints. We also report improved performance w.r.t. other very mature, highly optimized ASP systems in some benchmarks.

Autores: Joaquín Arias / Manuel Carro / Kyle Marple / Elmer Salazar / Gopal Gupta / 
Palabras Clave: constraints - goal-directed evaluation - predicate - stable model

3 -

5 - Modeling and Reasoning in Event Calculus Using Constraint Answer Set Programming

Automated commonsense reasoning is essential for building human-like AI systems featuring, for example, explainable AI. Event Calculus (EC) is a family of formalisms that model commonsense reasoning with a sound, logical basis. Previous attempts to mechanize reasoning using EC faced difficulties in the treatment of continuous change in dense domains (e.g., time and other physical quantities), constraints among variables, default negation, and the uniform application of different inference methods, among others. We propose the use of s(CASP), a query driven, top-down execution model for predicate Answer Set Programming with Constraints, to model and reason using EC. We show how EC scenarios can be modeled in s(CASP) and how its expressiveness makes it pos- sible to perform deductive and abductive reasoning tasks in domains featuring, for example, constraints involving dense time and fluents.

Autores: Joaquin Arias / Manuel Carro / 
Palabras Clave: Answer Set Programming - constraints - Event Calculus - Top-down execution