6 research outputs found

    Learning Disentangled Representations of Negation and Uncertainty

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    Negation and uncertainty modeling are long-standing tasks in natural language processing. Linguistic theory postulates that expressions of negation and uncertainty are semantically independent from each other and the content they modify. However, previous works on representation learning do not explicitly model this independence. We therefore attempt to disentangle the representations of negation, uncertainty, and content using a Variational Autoencoder. We find that simply supervising the latent representations results in good disentanglement, but auxiliary objectives based on adversarial learning and mutual information minimization can provide additional disentanglement gains.Comment: Accepted to ACL 2022. 18 pages, 7 figures. Code and data are available at https://github.com/jvasilakes/disentanglement-va

    Using Natural Language Processing to Mine Multiple Perspectives from Social Media and Scientific Literature.

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    This thesis studies how Natural Language Processing techniques can be used to mine perspectives from textual data. The first part of the thesis focuses on analyzing the text exchanged by people who participate in discussions on social media sites. We particularly focus on threaded discussions that discuss ideological and political topics. The goal is to identify the different viewpoints that the discussants have with respect to the discussion topic. We use subjectivity and sentiment analysis techniques to identify the attitudes that the participants carry toward one another and toward the different aspects of the discussion topic. This involves identifying opinion expressions and their polarities, and identifying the targets of opinion. We use this information to represent discussions in one of two representations: discussant attitude vectors or signed attitude networks. We use data mining and network analysis techniques to analyze these representations to detect rifts in discussion groups and study how the discussants split into subgroups with contrasting opinions. In the second part of the thesis, we use linguistic analysis to mine scholars perspectives from scientific literature through the lens of citations. We analyze the text adjacent to reference anchors in scientific articles as a means to identify researchers' viewpoints toward previously published work. We propose methods for identifying, extracting, and cleaning citation text. We analyze this text to identify the purpose (author's intention) and polarity (author's sentiment) of citation. Finally, we present several applications that can benefit from this analysis such as generating multi-perspective summaries of scientific articles and predicting future prominence of publications.PHDComputer Science & EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/99934/1/amjbara_1.pd

    Enhancing automatic extration of biomedical relations using different linguistic features extracted from text

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    Tesis inédita de la Universidad Complutense de Madrid, Facultad de Informática, Departamento de Ingeniería del Software e Inteligencia Artificial, leída el 08-06-2017La extracción de relaciones entre entidades es una tarea muy importante dentro del procesamiento de textos biomédicos. Cada vez hay más información sobre este tipo de interacciones almacenada en bases de datos, pero sin embargo la mayor cantidad de información relacionada con el tema está presente en artículos científicos o en recursos donde la información se almacena en formato textual.Las interacciones entre fármacos son, en particular, una preocupación generalizada en medicina, por esa razón la extracción automática de este tipo de relaciones es una tarea muy demandada en el procesamiento de textos biomédicos. Una interacción entre 2 fármacos normalmente se produce cuando un fármaco altera el nivel de actividad de otro fármaco. De acuerdo a los informes presentados por la Adminsitración Nacional de Alimentos y Fármacos de Estados Unidos y otros estudios reconocidos [1], cada año se producen más de 2 millones de interacciones mortales entre fármacos. Muchos investigadores y compañías farmaceúticas han desarrollado bases de datos donde estas interacciones son almacenadas. Sin embargo, la información más actualizada y valiosa sigue apareciendo sólo en documentos no estructurados en formato textual, incluyendo publicaciones científicas e informes técnicos.En esta tesis se estudian 3 conjuntos de características lingüísticas de los textos: negación,dependencia clausal y candidatos neutros. El objetivo final de la investigación es mejorar el rendimiento de la tarea de extracción de interacciones entre fármacos considerando las combinaciones de las características lingüísticas extraídas de los textos con métodos de aprendizaje basados en kernel...Extracting biomedical relations from texts is a relatively new, but rapidly growing researchfield in natural language processing (NLP). Due to the increasing number of biomedicalresearch publications and the key role of databases of biomedical relations in biological andmedical research, extracting biomedical relations from scientific articles and text resourcesis of utmost importance.Drug-drug interactions (DDI) are, in particular, a widespread concern in medicine, and thus,extracting this kind of interactions automatically from texts is of high demand in BioNLP. Adrug-drug interaction usually occurs when one drug alters the activity level of another drug.According to the reports prepared by the U. S. Food and Drug Administration (the FDA) andother acknowledged studies [1], over 2 million life-threatening DDIs occur in the UnitedStates every year. Many academic researchers and pharmaceutical companies havedeveloped relational and structural databases, where DDIs are recorded. Nevertheless,most up-to-date and valuable information is still found only in unstructured research textdocuments, including scientific publications and technical reports.In this thesis, three complementary, linguistically driven, feature sets, are studied: negation,clause dependency, and neutral candidates. The ultimate aim of this research is to enhancethe performance of the DDI extraction task by considering the combinations of theextracted features with well-established kernel methods...Depto. de Ingeniería de Software e Inteligencia Artificial (ISIA)Fac. de InformáticaTRUEunpu

    Analyzing, enhancing, optimizing and applying dependency analysis

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    Tesis inédita de la Universidad Complutense de Madrid, Facultad de Informática, Departamento de Ingeniería del Software e Inteligencia Artificial, leída el 19/12/2012Los analizadores de dependencias estadísticos han sido mejorados en gran medida durante los últimos años. Esto ha sido posible gracias a los sistemas basados en aprendizaje automático que muestran una gran precisión. Estos sistemas permiten la generación de parsers para idiomas en los que se disponga de un corpus adecuado sin causar, para ello, un gran esfuerzo en el usuario final. MaltParser es uno de estos sistemas. En esta tesis hemos usado sistemas del estado del arte, para mostrar una serie de contribuciones completamente relacionadas con el procesamiento de lenguaje natural (PLN) y análisis de dependencias: (i) Estudio del problema del análisis de dependencias demostrando la homogeneidad en la precisión y mostrando contribuciones interesantes sobre la longitud de las frases, el tamaño de los corpora de entrenamiento y como evaluamos los parsers. (ii) Hemos estudiado además algunas maneras de mejorar la precisión modificando el flujo de análisis de dos maneras distintas, analizando algunos segmentos de las frases de manera separada, y modificando el comportamiento interno de los algoritmos de parsing. (iii) Hemos investigado la selección automática de atributos para aprendizaje máquina para analizadores de dependencias basados en transiciones que consideramos un importante problema y algo que realmente es necesario resolver dado el estado de la cuestión, ya que además puede servir para resolver de mejor manera tareas relacionadas con el análisis de dependencias. (iv) Finalmente, hemos aplicado el análisis de dependencias para resolver algunos problemas, hoy en día importantes, para el procesamiento de lenguage natural (PLN) como son la simplificación de textos o la inferencia del alcance de señales de negación. Por último, añadir que el conocimiento adquirido en la realización de esta tesis puede usarse para implementar aplicaciones basadas en análisis de dependencias más robustas en PLN o en otras áreas relacionadas, como se demuestra a lo largo de la tesis. [ABSTRACT] Statistical dependency parsing accuracy has been improved substantially during the last years. One of the main reasons is the inclusion of data- driven (or machine learning) based methods. Machine learning allows the development of parsers for every language that has an adequate training corpus without requiring a great effort. MaltParser is one of such systems. In the present thesis we have used state of the art systems (mainly Malt- Parser), to show some contributions in four different areas inherently related to natural language processing (NLP) and dependency parsing: (i) We stu- died the parsing problem demonstrating the homogeneity of the performance and showing interesting contributions about sentence length, corpora size and how we normally evaluate the parsers. (ii) We have also tried some ways of improving the parsing accuracy by modifying the flow of analysis, parsing some segments of the sentences separately by finally constructing a parsing combination problem. We also studied the modification of the inter- nal behavior of the parsers focusing on the root of dependency structures, which is an important part of what a dependency parser parses and worth studying. (iii) We have researched automatic feature selection and parsing optimization for transition based parsers which we consider an important problem and something that definitely needs to be done in dependency par- sing in order to solve parsing problems in a more successful way. And (iv) we have applied syntactic dependency structures and dependency parsing to solve some Natural Language Processing (NLP) problems such as text simplification and inferring the scope of negation cues. Furthermore, the knowledge acquired when developing this thesis could be used to implement more robust dependency parsing–based applications in different NLP (or related) areas, as we demonstrate in the present thesis.Depto. de Ingeniería de Software e Inteligencia Artificial (ISIA)Fac. de InformáticaTRUEunpu
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