Text as scene: discourse deixis and bridging relations

En este artículo se presenta un nuevo marco, “el texto como escena”, que establece las bases para la anotación de dos relaciones de correferencia: la deixis discursiva y las relaciones de bridging. La incorporación de lo que llamamos escenas textuales y contextuales proporciona unas directrices de anotación más flexibles, que diferencian claramente entre tipos de categorías generales. Un marco como éste, capaz de tratar la deixis discursiva y las relaciones de bridging desde una perspectiva común, tiene como objetivo mejorar el bajo grado de acuerdo entre anotadores obtenido por esquemas de anotación anteriores, que son incapaces de captar las referencias vagas inherentes a estos dos tipos de relaciones. Las directrices aquí presentadas completan el esquema de anotación diseñado para enriquecer el corpus español CESS-ECE con información correferencial y así construir el corpus CESS-Ancora.This paper presents a new framework, “text as scene”, which lays the foundations for the annotation of two coreferential links: discourse deixis and bridging relations. The incorporation of what we call textual and contextual scenes provides more flexible annotation guidelines, broad type categories being clearly differentiated. Such a framework that is capable of dealing with discourse deixis and bridging relations from a common perspective aims at improving the poor reliability scores obtained by previous annotation schemes, which fail to capture the vague references inherent in both these links. The guidelines presented here complete the annotation scheme designed to enrich the Spanish CESS-ECE corpus with coreference information, thus building the CESS-Ancora corpus.This paper has been supported by the FPU grant (AP2006-00994) from the Spanish Ministry of Education and Science. It is based on work supported by the CESS-ECE (HUM2004-21127), Lang2World (TIN2006- 15265-C06-06), and Praxem (HUM2006- 27378-E) projects

AnaPro, Tool for Identification and Resolution of Direct Anaphora in Spanish

Introduction Anaphora is a relation of coreference between linguistic terms. According to Webster’s dictionary: “It is the use of a grammatical substitute (as a pronoun or a pro-verb) to refer to the denotation of a preceding word or group of words; also : the relation between a grammatical substitute and its antecedent.” Therefore, anaphora is a discourse relation. Anaphora resolution is very important in Natural Language Processing (NLP). This work is part of Project OM* (Ontology Merging), which seeks to build a large ontology by fusing smaller ontologies extracted from textual documents. An important part of the project is to analyze the sentences in a document with the goal to transform that text into an ontology that comprises its contents. A brief description of Project OM* follows.AnaPro is software that solves direct anaphora in Spanish, specifically pronouns: it finds the noun or group of words to which the pronoun refers. It locates in the previous sentenc es the referent or antecedent which the pronoun replaces. An example of a direct anaphora solved is the pronoun “ he” in the sentence “He is sad.” Much of the work on anaphora has been done for texts in English; thus , we specifically focus on Spanish documents. AnaPro directly supports text analys is (to understand what a document says ), a non trivial task since there are different writing styles, references, idiomatic expressions, etc. The problem grows if t he analyzer is a computer, because they lack “common sense” (which persons possess) . Hence, before text analysis, its preprocessing is required, in order to assign tags (noun, verb,...) to each word, find the stems, disambiguate nouns, verbs, prepositions, identify colloquial expressions, i dentify and resolve anaphor a, among other chores. AnaPro works for Spanish sentences. It is a novel procedure, since it is automatic (no user intervenes during the resolution) and it does not need dictionaries. It employs heu ristics procedures to discover the semantics and help in the decisions; they are rather easy to implement and use li mited knowledge. Nevertheless, its results are good (81% of correct answers, at least). However, more tests will give a better idea of its goodness.Authors I.T. and E.V. would like to acknowledge ESCOM-IPN, where they defended their thesis, #20110083 , which gives a more detailed description of AnaPro. Work herein reported was partially sponsored by CONACYT Grant #128163 (Project OM*), by IPN and by SNI and UAEM

Translation of Pronominal Anaphora between English and Spanish: Discrepancies and Evaluation

This paper evaluates the different tasks carried out in the translation of pronominal anaphora in a machine translation (MT) system. The MT interlingua approach named AGIR (Anaphora Generation with an Interlingua Representation) improves upon other proposals presented to date because it is able to translate intersentential anaphors, detect co-reference chains, and translate Spanish zero pronouns into English---issues hardly considered by other systems. The paper presents the resolution and evaluation of these anaphora problems in AGIR with the use of different kinds of knowledge (lexical, morphological, syntactic, and semantic). The translation of English and Spanish anaphoric third-person personal pronouns (including Spanish zero pronouns) into the target language has been evaluated on unrestricted corpora. We have obtained a precision of 80.4% and 84.8% in the translation of Spanish and English pronouns, respectively. Although we have only studied the Spanish and English languages, our approach can be easily extended to other languages such as Portuguese, Italian, or Japanese

Computational Approach to Anaphora Resolution in Spanish Dialogues

This paper presents an algorithm for identifying noun-phrase antecedents of pronouns and adjectival anaphors in Spanish dialogues. We believe that anaphora resolution requires numerous sources of information in order to find the correct antecedent of the anaphor. These sources can be of different kinds, e.g., linguistic information, discourse/dialogue structure information, or topic information. For this reason, our algorithm uses various different kinds of information (hybrid information). The algorithm is based on linguistic constraints and preferences and uses an anaphoric accessibility space within which the algorithm finds the noun phrase. We present some experiments related to this algorithm and this space using a corpus of 204 dialogues. The algorithm is implemented in Prolog. According to this study, 95.9% of antecedents were located in the proposed space, a precision of 81.3% was obtained for pronominal anaphora resolution, and 81.5% for adjectival anaphora

An Empirical Approach to Temporal Reference Resolution

This paper presents the results of an empirical investigation of temporal reference resolution in scheduling dialogs. The algorithm adopted is primarily a linear-recency based approach that does not include a model of global focus. A fully automatic system has been developed and evaluated on unseen test data with good results. This paper presents the results of an intercoder reliability study, a model of temporal reference resolution that supports linear recency and has very good coverage, the results of the system evaluated on unseen test data, and a detailed analysis of the dialogs assessing the viability of the approach.Comment: 13 pages, latex using aclap.st

Review of coreference resolution in English and Persian

Coreference resolution (CR) is one of the most challenging areas of natural language processing. This task seeks to identify all textual references to the same real-world entity. Research in this field is divided into coreference resolution and anaphora resolution. Due to its application in textual comprehension and its utility in other tasks such as information extraction systems, document summarization, and machine translation, this field has attracted considerable interest. Consequently, it has a significant effect on the quality of these systems. This article reviews the existing corpora and evaluation metrics in this field. Then, an overview of the coreference algorithms, from rule-based methods to the latest deep learning techniques, is provided. Finally, coreference resolution and pronoun resolution systems in Persian are investigated.Comment: 44 pages, 11 figures, 5 table