Cross-lingual RST Discourse Parsing

Discourse parsing is an integral part of understanding information flow and argumentative structure in documents. Most previous research has focused on inducing and evaluating models from the English RST Discourse Treebank. However, discourse treebanks for other languages exist, including Spanish, German, Basque, Dutch and Brazilian Portuguese. The treebanks share the same underlying linguistic theory, but differ slightly in the way documents are annotated. In this paper, we present (a) a new discourse parser which is simpler, yet competitive (significantly better on 2/3 metrics) to state of the art for English, (b) a harmonization of discourse treebanks across languages, enabling us to present (c) what to the best of our knowledge are the first experiments on cross-lingual discourse parsing.Comment: To be published in EACL 2017, 13 page

Joint Syntacto-Discourse Parsing and the Syntacto-Discourse Treebank

Discourse parsing has long been treated as a stand-alone problem independent from constituency or dependency parsing. Most attempts at this problem are pipelined rather than end-to-end, sophisticated, and not self-contained: they assume gold-standard text segmentations (Elementary Discourse Units), and use external parsers for syntactic features. In this paper we propose the first end-to-end discourse parser that jointly parses in both syntax and discourse levels, as well as the first syntacto-discourse treebank by integrating the Penn Treebank with the RST Treebank. Built upon our recent span-based constituency parser, this joint syntacto-discourse parser requires no preprocessing whatsoever (such as segmentation or feature extraction), achieves the state-of-the-art end-to-end discourse parsing accuracy.Comment: Accepted at EMNLP 201

Cross-lingual and cross-domain discourse segmentation of entire documents

Discourse segmentation is a crucial step in building end-to-end discourse parsers. However, discourse segmenters only exist for a few languages and domains. Typically they only detect intra-sentential segment boundaries, assuming gold standard sentence and token segmentation, and relying on high-quality syntactic parses and rich heuristics that are not generally available across languages and domains. In this paper, we propose statistical discourse segmenters for five languages and three domains that do not rely on gold pre-annotations. We also consider the problem of learning discourse segmenters when no labeled data is available for a language. Our fully supervised system obtains 89.5% F1 for English newswire, with slight drops in performance on other domains, and we report supervised and unsupervised (cross-lingual) results for five languages in total.Comment: To appear in Proceedings of ACL 201

GumDrop at the DISRPT2019 Shared Task: A Model Stacking Approach to Discourse Unit Segmentation and Connective Detection

In this paper we present GumDrop, Georgetown University's entry at the DISRPT 2019 Shared Task on automatic discourse unit segmentation and connective detection. Our approach relies on model stacking, creating a heterogeneous ensemble of classifiers, which feed into a metalearner for each final task. The system encompasses three trainable component stacks: one for sentence splitting, one for discourse unit segmentation and one for connective detection. The flexibility of each ensemble allows the system to generalize well to datasets of different sizes and with varying levels of homogeneity.Comment: Proceedings of Discourse Relation Parsing and Treebanking (DISRPT2019

Elaboration of a RST Chinese Treebank

[EN] As a subfield of Artificial Intelligence (AI), Natural Language Processing (NLP) aims to automatically process human languages. Fruitful achievements of variant studies from different research fields for NLP exist. Among these research fields, discourse analysis is becoming more and more popular. Discourse information is crucial for NLP studies. As the most spoken language in the world, Chinese occupy a very important position in NLP analysis. Therefore, this work aims to present a discourse treebank for Chinese, whose theoretical framework is Rhetorical Structure Theory (RST) (Mann and Thompson, 1988). In this work, 50 Chinese texts form the research corpus and the corpus can be consulted from the following aspects: segmentation, central unit (CU) and discourse structure. Finally, we create an open online interface for the Chinese treebank.[EU] Adimen Artifizialaren (AA) barneko arlo bat izanez, Hizkuntzaren Prozesamenduak (HP) giza-hizkuntzak automatikoko prozesatzea du helburu. Arlo horretako ikasketa anitzetan lorpen emankor asko eman dira. Ikasketa-arlo ezberdin horien artean, diskurtso-analisia gero eta ezagunagoa da. Diskurtsoko inforamzioa interes handikoa da HPko ikasketetan. Munduko hiztun gehien duen hizkuntza izanda, txinera aztertzea oso garrantzitsua da HPan egiten ari diren ikasketetarako. Hori dela eta, lan honek txinerako diskurtso-egituraz etiketaturiko zuhaitz-banku bat aurkeztea du helburu, Egitura Erretorikoaren Teoria (EET) (Mann eta Thompson, 1988) oinarrituta. Lan honetan, ikerketa-corpusa 50 testu txinatarrez osatu da, ea zuhaitz-bankua hiru etiketatze-mailatan aurkeztuko da: segmentazioa, unitate zentrala (UZ) eta diskurtso-egitura. Azkenik, corpusa webgune batean argitaratu da zuhaitz-bankua kontsultatzeko

Maximum Entropy Models For Natural Language Ambiguity Resolution

This thesis demonstrates that several important kinds of natural language ambiguities can be resolved to state-of-the-art accuracies using a single statistical modeling technique based on the principle of maximum entropy. We discuss the problems of sentence boundary detection, part-of-speech tagging, prepositional phrase attachment, natural language parsing, and text categorization under the maximum entropy framework. In practice, we have found that maximum entropy models offer the following advantages: State-of-the-art Accuracy: The probability models for all of the tasks discussed perform at or near state-of-the-art accuracies, or outperform competing learning algorithms when trained and tested under similar conditions. Methods which outperform those presented here require much more supervision in the form of additional human involvement or additional supporting resources. Knowledge-Poor Features: The facts used to model the data, or features, are linguistically very simple, or knowledge-poor but yet succeed in approximating complex linguistic relationships. Reusable Software Technology: The mathematics of the maximum entropy framework are essentially independent of any particular task, and a single software implementation can be used for all of the probability models in this thesis. The experiments in this thesis suggest that experimenters can obtain state-of-the-art accuracies on a wide range of natural language tasks, with little task-specific effort, by using maximum entropy probability models

EusEduSeg: Un Segmentador Discursivo para el Euskera Basado en Dependencias

We present the first discursive segmenter for Basque implemented by heuristics based on syntactic dependencies and linguistic rules. Preliminary experiments show F1 values of more than 85% in automatic EDU segmentation for Basque.Presentamos en este artículo el primer segmentador discursivo para el euskera (EusEduSeg) implementado con heurísticas basadas en dependencias sintácticas y reglas lingüísticas. Experimentos preliminares muestran resultados de más del 85 % F1 en el etiquetado de EDUs sobre el Basque RST TreeBank

Detección de la unidad central en dos géneros y lenguajes diferentes: un estudio preliminar en portugués brasileño y euskera

The aim of this paper is to present the development of a rule-based automatic detector which determines the main idea or the most pertinent discourse unit in two different languages such as Basque and Brazilian Portuguese and in two distinct genres such as scientific abstracts and argumentative answers. The central unit (CU) may be of interest to understand texts regarding relational discourse structure and it can be applied to Natural Language Processing (NLP) tasks such as automatic summarization, question-answer systems or sentiment analysis. In the case of argumentative answer genre, the identification of CU is an essential step for an eventual implementation of an automatic evaluator for this genre. The theoretical background which underlies the paper is Mann and Thompson’s (1988) Rhetorical Structure Theory (RST), following discourse segmentation and CU annotation. Results show that the CUs in different languages and in different genres are detected automatically with similar results, although there is space for improvement.El objetivo de este trabajo es presentar las mejoras de un detector automático basado en reglas que determina la idea principal o unidad discursiva más pertinente de dos lenguas tan diferentes como el euskera y el portugués de Brasil y en dos géneros muy distintos como son los resúmenes de los artículos científicos y las respuestas argumentativas. La unidad central (CU, por sus siglas en inglés) puede ser de interés para entender los textos partiendo de la estructura discursiva relacional y poderlo aplicar en tareas de Procesamiento del Lenguaje Natural (PLN) tales como resumen automático, sistemas de pregunta-respuesta o análisis de sentimiento. En los textos de respuesta argumentativa, identificar la CU es un paso esencial para un evaluador automático de considere la estructura discursiva de dichos textos. El marco teórico en el que hemos desarrollado el trabajo es la Rhetorical Structure Theory (RST) de Mann y Thompson (1988), que parte de la segmentación discursiva y finaliza con la anotación de la unidad central. Los resultados demuestran que las unidades centrales en diferentes lenguas y géneros son detectadas con similares resultados automáticamente, aunque todavía hay espacio para mejora