Treating Coordination with Datalog Grammars

In previous work we studied a new type of DCGs, Datalog grammars, which are inspired on database theory. Their efficiency was shown to be better than that of their DCG counterparts under (terminating) OLDT-resolution. In this article we motivate a variant of Datalog grammars which allows us a meta-grammatical treatment of coordination. This treatment improves in some respects over previous work on coordination in logic grammars, although more research is needed for testing it in other respects

Paralelismo sintáctico-semántico para el tratamiento de elementos extrapuestos en textos no restringidos

En este artículo presentamos un método basado en la teoría del paralelismo para la identificación y resolución de elementos extrapuestos en textos no restringidos. Esta teoría de paralelismo está basada en (Palomar 96) y se amplía con el desarrollo de técnicas de análisis parcial –en las que se estudia las partes relevantes del texto- que facilitan la resolución de los fenómenos lingüísticos. Nos basaremos en los programas Datalog extendidos (Dahl 94) (Dahl 95) como herramienta para la definición e implementación de gramáticas. Éstas no están basadas en reglas gramaticales sino en la detección de información relevante, relajando el proceso y ampliando el conjunto potencial de textos analizables.Este artículo ha sido subvencionado por el proyecto CICYT nº TIC97-0671-C02-01/02

CHR Grammars

A grammar formalism based upon CHR is proposed analogously to the way Definite Clause Grammars are defined and implemented on top of Prolog. These grammars execute as robust bottom-up parsers with an inherent treatment of ambiguity and a high flexibility to model various linguistic phenomena. The formalism extends previous logic programming based grammars with a form of context-sensitive rules and the possibility to include extra-grammatical hypotheses in both head and body of grammar rules. Among the applications are straightforward implementations of Assumption Grammars and abduction under integrity constraints for language analysis. CHR grammars appear as a powerful tool for specification and implementation of language processors and may be proposed as a new standard for bottom-up grammars in logic programming. To appear in Theory and Practice of Logic Programming (TPLP), 2005Comment: 36 pp. To appear in TPLP, 200

Domes as a Prodigal Shape in Synthesis-Enhanced Parsers.

Abstract. Research on logic based bottom-up parsing -in particular, around Constraint Handling Rule Grammars [3]-is uncovering shape as an untapped fertile ground for natural language processing in general, and for bottom-up parsing and grammar induction in particula

Tabulation for multi-purpose partial parsing

Efficient partial parsing systems (chunkers) are urgently required by various natural language application areas as these parsers always produce partially parsed text even when the text does not fully fit existing lexica and grammars. Availability of partially parsed corpora is absolutely necessary for extracting various kinds of information that may then be fed into those systems, increasing their processing power. In this paper, we propose an efficient partial parsing scheme based on chart parsing that is flexible enough to support both normal parsing tasks and diagnosis in previously obtained partial parses of possible causes (kinds of faults) that led to those partial parses instead of complete parses. Through the use of the built-in tabulation capabilites of the DyALog system, we implemented a partial parser that runs as fast as the best non-deterministic parsers. In this paper we ellaborate on the implementation of two different grammar formalisms: Definite Clause Grammars (DCG) extended with head declarations and Bound Movement Grammars (BMG)

Machine ethics via logic programming

Machine ethics is an interdisciplinary field of inquiry that emerges from the need of imbuing autonomous agents with the capacity of moral decision-making. While some approaches provide implementations in Logic Programming (LP) systems, they have not exploited LP-based reasoning features that appear essential for moral reasoning. This PhD thesis aims at investigating further the appropriateness of LP, notably a combination of LP-based reasoning features, including techniques available in LP systems, to machine ethics. Moral facets, as studied in moral philosophy and psychology, that are amenable to computational modeling are identified, and mapped to appropriate LP concepts for representing and reasoning about them. The main contributions of the thesis are twofold. First, novel approaches are proposed for employing tabling in contextual abduction and updating – individually and combined – plus a LP approach of counterfactual reasoning; the latter being implemented on top of the aforementioned combined abduction and updating technique with tabling. They are all important to model various issues of the aforementioned moral facets. Second, a variety of LP-based reasoning features are applied to model the identified moral facets, through moral examples taken off-the-shelf from the morality literature. These applications include: (1) Modeling moral permissibility according to the Doctrines of Double Effect (DDE) and Triple Effect (DTE), demonstrating deontological and utilitarian judgments via integrity constraints (in abduction) and preferences over abductive scenarios; (2) Modeling moral reasoning under uncertainty of actions, via abduction and probabilistic LP; (3) Modeling moral updating (that allows other – possibly overriding – moral rules to be adopted by an agent, on top of those it currently follows) via the integration of tabling in contextual abduction and updating; and (4) Modeling moral permissibility and its justification via counterfactuals, where counterfactuals are used for formulating DDE.Fundação para a Ciência e a Tecnologia (FCT)-grant SFRH/BD/72795/2010 ; CENTRIA and DI/FCT/UNL for the supplementary fundin

Reglas genéricas: objetos, reglas y excepciones en el procesamiento del lenguaje natural

Tesis doctoral inédita leida en la Universidad Autónoma de Madrid. Facultad de Ciencias, Departamento de Ingenieria Informática. Fecha de lectura: 28-9-199

Provenance, Incremental Evaluation, and Debugging in Datalog

The Datalog programming language has recently found increasing traction in research and industry. Driven by its clean declarative semantics, along with its conciseness and ease of use, Datalog has been adopted for a wide range of important applications, such as program analysis, graph problems, and networking. To enable this adoption, modern Datalog engines have implemented advanced language features and high-performance evaluation of Datalog programs. Unfortunately, critical infrastructure and tooling to support Datalog users and developers are still missing. For example, there are only limited tools addressing the crucial debugging problem, where developers can spend up to 30% of their time finding and fixing bugs. This thesis addresses Datalog’s tooling gaps, with the ultimate goal of improving the productivity of Datalog programmers. The first contribution is centered around the critical problem of debugging: we develop a new debugging approach that explains the execution steps taken to produce a faulty output. Crucially, our debugging method can be applied for large-scale applications without substantially sacrificing performance. The second contribution addresses the problem of incremental evaluation, which is necessary when program inputs change slightly, and results need to be recomputed. Incremental evaluation allows this recomputation to happen more efficiently, without discarding the previous results and recomputing from scratch. Finally, the last contribution provides a new incremental debugging approach that identifies the root causes of faulty outputs that occur after an incremental evaluation. Incremental debugging focuses on the relationship between input and output and can provide debugging suggestions to amend the inputs so that faults no longer occur. These techniques, in combination, form a corpus of critical infrastructure and tooling developments for Datalog, allowing developers and users to use Datalog more productively