Sentiment classification of long newspaper articles based on automatically generated thesaurus with various semantic relationships

The paper describes a new approach for sentiment classification of long texts from newspapers using an automatically generated thesaurus. An important part of the proposed approach is specialized thesaurus creation and computation of term's sentiment polarities based on relationships between terms. The approach's efficiency has been proved on a corpus of articles about American immigrants. The experiments showed that the automatically created thesaurus provides better classification quality than manual ones, and generally for this task our approach outperforms existing ones

Text Classification by Genre Based on Rhythm Features

The article is devoted to the analysis of the rhythm of texts of different genres: fiction novels, advertisements, scientific articles, reviews, tweets, and political articles. The authors identified lexico-grammatical figures in the texts: anaphora, epiphora, diacope, aposiopesis, etc., that are markers of the text rhythm. On their basis, statistical features were calculated that describe quantitatively and structurally these rhythm features.The resulting text model was visualized for statistical analysis using boxplots and heat maps that showed differences in the rhythm of texts of different genres. The boxplots showed that almost all genres differ from each other in terms of the overall density of rhythm features. Heatmaps showed different rhythm patterns across genres. Further, the rhythm features were successfully used to classify texts into six genres. The classification was carried out in two ways: a binary classification for each genre in order to separate a particular genre from the rest genres, and a multi-class classification of the text corpus into six genres at once. Two text corpora in English and Russian were used for the experiments. Each corpus contains 100 fiction novels, scientific articles, advertisements and tweets, 50 reviews and political articles, i.e. a total of 500 texts. The high quality of the classification with neural networks showed that rhythm features are a good marker for most genres, especially fiction. The experiments were carried out using the ProseRhythmDetector software tool for Russian and English languages. Text corpora contains 300 texts for each language

A survey on thesauri application in automatic natural language processing

This paper is devoted to investigate efficiency of thesauri use in popular natural language processing (NLP) fields: information retrieval and analysis of texts and subject areas. A thesaurus is a natural language resource that models a subject area and can reflect human expert's knowledge in many NLP tasks. The main target of this survey is to determine how much thesauri affect processing quality and where they can provide better performance. We describe studies that use different types of thesauri, discuss contribution of the thesaurus into achieved results, and propose directions for future research in the thesaurus field

Sentiment Classification of Russian Texts Using Automatically Generated Thesaurus

This paper is devoted to an approach for sentiment classification of Russian texts applying an automatic thesaurus of the subject area. This approach consists of a standard machine learning classifier and a procedure embedded into it, that uses the- saurus relationships for better sentiment analysis. The thesaurus is generated fully automatically and does not require expert’s involvement into classification process. Experiments conducted with the approach and four Russian-language text corpora, show effectiveness of thesaurus application to sentiment classification

Analysis of the Impact of the Stylometric Characteristics of Different Levels for the Verification of Authors of the Prose

This article is dedicated to the analysis of various stylometric characteristics combinations of different levels for the quality of verification of authorship of Russian, English and French prose texts. The research was carried out for both low-level stylometric characteristics based on words and symbols and higher-level structural characteristics.All stylometric characteristics were calculated automatically with the help of the ProseRhythmDetector program. This approach gave a possibility to analyze the works of a large volume and of many writers at the same time. During the work, vectors of stylometric characteristics of the level of symbols, words and structure were compared to each text. During the experiments, the sets of parameters of these three levels were combined with each other in all possible ways. The resulting vectors of stylometric characteristics were applied to the input of various classifiers to perform verification and identify the most appropriate classifier for solving the problem. The best results were obtained with the help of the AdaBoost classifier. The average F-score for all languages turned out to be more than 92 %. Detailed assessments of the quality of verification are given and analyzed for each author. Use of high-level stylometric characteristics, in particular, frequency of using N-grams of POS tags, offers the prospect of a more detailed analysis of the style of one or another author. The results of the experiments show that when the characteristics of the structure level are combined with the characteristics of the level of words and / or symbols, the most accurate results of verification of authorship for literary texts in Russian, English and French are obtained. Additionally, the authors were able to conclude about a different degree of impact of stylometric characteristics for the quality of verification of authorship for different languages

Sentiment Classification into Three Classes Applying Multinomial Bayes Algorithm, N-grams, and Thesaurus

The paper is devoted to development of the method that classi?es texts in English and Russian by sentiments into positive, negative, and neutral. The proposed method is based on the Multinomial Naive Bayes classi?er with additional n-grams application. The classi?er is trained either on three classes, or on two contrasting classes with a threshold to separate neutral texts. Experiments with texts on various topics showed signi?cant improvement of classification quality for reviews from a particular domain. Besides, the analysis of thesaurus relationships application to sentiment classification into three classes was done, however it did not show significant improvement of the classification results

An approach to automated thesaurus construction using clusterization-based dictionary analysis

In the paper an automated approach for construction of the terminological thesaurus for a specific domain is proposed. It uses an explanatory dictionary as the initial text corpus and a controlled vocabulary related to the target lexicon to initiate extraction of the terms for the thesaurus. Subdivision of the terms into semantic clusters is based on the CLOPE clustering algorithm. The approach diminishes the cost of the thesaurus creation by involving the expert only once during the whole construction process, and only for analysis of a small subset of the initial dictionary. To validate the performance of the proposed approach the authors successfully constructed a thesaurus in the cardiology domain

Анализ использования различных типов связей между терминами тезауруса, сгенерированного с помощью гибридных методов, в задачах классификации текстов

The main purpose of the article is to analyze how effectively different types of thesaurus relations can be used for solutions of text classification tasks. The basis of the study is an automatically generated thesaurus of a subject area, that contains three types of relations: synonymous, hierarchical and associative. To generate the thesaurus the authors use a hybrid method based on several linguistic and statistical algorithms for extraction of semantic relations. The method allows to create a thesaurus with a sufficiently large number of terms and relations among them. The authors consider two problems: topical text classification and sentiment classification of large newspaper articles. To solve them, the authors developed two approaches that complement standard algorithms with a procedure that take into account thesaurus relations to determine semantic features of texts. The approach to topical classification includes the standard unsupervised BM25 algorithm and the procedure, that take into account synonymous and hierarchical relations of the thesaurus of the subject area. The approach to sentiment classification consists of two steps. At the first step, a thesaurus is created, whose terms weight polarities are calculated depending on the term occurrences in the training set or on the weights of related thesaurus terms. At the second step, the thesaurus is used to compute the features of words from texts and to classify texts by the algorithm SVM or Naive Bayes. In experiments with text corpora BBCSport, Reuters, PubMed and the corpus of articles about American immigrants, the authors varied the types of thesaurus relations that are involved in the classification and the degree of their use. The results of the experiments make it possible to evaluate the efficiency of the application of thesaurus relations for classification of raw texts and to determine under what conditions certain relationships affect more or less. In particular, the most useful thesaurus connections are synonymous and hierarchical, as they provide a better quality of classification. Цель данной статьи — проанализировать, насколько эффективно могут применяться различные типы тезаурусных связей в задачах классификации текстов. Основой исследования является автоматически сгенерированный тезаурус предметной области, содержащий три типа связей: синонимические, иерархические и ассоциативные. Для генерации тезауруса используется гибридный метод, основанный на нескольких лингвистических и статистических алгоритмах выделения семантических связей и позволяющий создать тезаурус с достаточно большим числом терминов и связей между ними. Авторы рассматривают две задачи: тематическая классификация текстов и классификация больших новостных статей по тональности. Для решения каждой из них авторами были использованы два подхода, каждый из которых дополняет стандартные алгоритмы процедурой, применяющей связи тезауруса для определения семантических особенностей текстов. Подход к тематической классификации включает в себя стандартный алгоритм BM25 вида «обучение без учителя» и процедуру, использующую синонимические и иерархические связи тезауруса предметной области. Подход к классификации по тональности состоит из двух шагов. На первом шаге создается тезаурус, тональные веса терминов которого считаются в зависимости от частоты встречаемости в обучаемой выборке или от веса соседей по тезаурусу. На втором шаге тезаурус применяется для вычисления признаков слов из текстов и классификации текстов методом опорных векторов или наивным байесовским классификатором. В экспериментах с корпусами BBCSport, Reuters, PubMed и корпусом статей об американских иммигрантах авторы варьировали типы связей, которые участвуют в классификации, и степень их использования. Результаты экспериментов позволяют оценить эффективность применения тезаурусных связей для классификации текстов на естественном языке и определить, при каких условиях те или иные связи имеют большую значимость. В частности, наиболее полезными тезаурусными связями оказались синонимические и иерархические, так как они обеспечивает лучшее качество классификации.

Классификация текстов по уровням CEFR с использованием методов машинного обучения и языковой модели BERT

This paper presents a study of the problem of automatic classification of short coherent texts (essays) in English according to the levels of the international CEFR scale. Determining the level of text in natural language is an important component of assessing students knowledge, including checking open tasks in e-learning systems. To solve this problem, vector text models were considered based on stylometric numerical features of the character, word, sentence structure levels. The classification of the obtained vectors was carried out by standard machine learning classifiers. The article presents the results of the three most successful ones: Support Vector Classifier, Stochastic Gradient Descent Classifier, LogisticRegression. Precision, recall and F-score served as quality measures. Two open text corpora, CEFR Levelled English Texts and BEA-2019, were chosen for the experiments. The best classification results for six CEFR levels and sublevels from A1 to C2 were shown by the Support Vector Classifier with F-score 67 % for the CEFR Levelled English Texts. This approach was compared with the application of the BERT language model (six different variants). The best model, bert-base-cased, provided the F-score value of 69 %. The analysis of classification errors showed that most of them are between neighboring levels, which is quite understandable from the point of view of the domain. In addition, the quality of classification strongly depended on the text corpus, that demonstrated a significant difference in F-scores during application of the same text models for different corpora. In general, the obtained results showed the effectiveness of automatic text level detection and the possibility of its practical application.В данной работе представлено исследование задачи автоматической классификации коротких связных текстов (эссе) на английском языке по уровням международной шкалы CEFR. Определение уровня текста на естественном языке является важной составляющей оценки знаний учащихся, в том числе для проверки открытых заданий в системах электронного обучения. Для решения этой задачи были рассмотрены векторные модели текста на основе стилометрических числовых характеристик уровня символов, слов, структуры предложения. Классификация полученных векторов осуществлялась стандартными классификаторами машинного обучения. В статье приведены результаты трёх наиболее успешных: Support Vector Classifier, Stochastic Gradient Descent Classifier, LogisticRegression. Оценкой качества послужили точность, полнота и F"=мера. Для экспериментов были выбраны два открытых корпуса текстов CEFR Levelled English Texts и BEA"=2019. Лучшие результаты классификации по шести уровням и подуровням CEFR от A1 до C2 показал Support Vector Classifier с F"=мерой 67 % для корпуса CEFR Levelled English Texts. Этот подход сравнивался с применением языковой модели BERT (шесть различных вариантов). Лучшая модель bert"=base"=cased обеспечила значение F"=меры 69 %. Анализ ошибок классификации показал, что большая их часть допущена между соседними уровнями, что вполне объяснимо с точки зрения предметной области. Кроме того, качество классификации сильно зависело от корпуса текстов, что продемонстрировало существенное различие F"=меры в ходе применения одинаковых моделей текста для разных корпусов. В целом, полученные результаты показали эффективность автоматического определения уровня текста и возможность его практического применения

Русскоязычные тезаурусы: автоматизированное построение и применение в задачах обработки текстов на естественном языке

The paper reviews the existing Russian-language thesauri in digital form and methods of their automatic construction and application. The authors analyzed the main characteristics of open access thesauri for scientific research, evaluated trends of their development, and their effectiveness in solving natural language processing tasks. The statistical and linguistic methods of thesaurus construction that allow to automate the development and reduce labor costs of expert linguists were studied. In particular, the authors considered algorithms for extracting keywords and semantic thesaurus relationships of all types, as well as the quality of thesauri generated with the use of these tools. To illustrate features of various methods for constructing thesaurus relationships, the authors developed a combined method that generates a specialized thesaurus fully automatically taking into account a text corpus in a particular domain and several existing linguistic resources. With the proposed method, experiments were conducted with two Russian-language text corpora from two subject areas: articles about migrants and tweets. The resulting thesauri were assessed by using an integrated assessment developed in the previous authors’ study that allows to analyze various aspects of the thesaurus and the quality of the generation methods. The analysis revealed the main advantages and disadvantages of various approaches to the construction of thesauri and the extraction of semantic relationships of different types, as well as made it possible to determine directions for future study.В работе выполнен обзор существующих электронных русскоязычных тезаурусов и методов их автоматического построения и применения. Авторы провели анализ основных характеристик тезаурусов, находящихся в открытом доступе, для научных исследований, оценили динамику их развития и эффективность в решении задач по обработке естественного языка. Были исследованы статистические и лингвистические методы построения тезаурусов, которые позволяют автоматизировать разработку и уменьшить затраты на труд экспертов-лингвистов. В частности, рассматривались алгоритмы выделения ключевых терминов из текстов и семантических тезаурусных связей всех типов, а также качество применения получившихся в результате их работы тезаурусов. Для наглядной иллюстрации особенностей различных методов построения тезаурусных связей был разработан комбинированный метод, генерирующий специализированный тезаурус полностью автоматически на основе корпуса текстов предметной области и нескольких существующих лингвистических ресурсов. С использованием предложенного метода были проведены эксперименты с русскоязычными корпусами текстов из двух предметных областей: статьи о мигрантах и твиты. Для анализа полученных тезаурусов использовалась комплексная оценка, разработанная авторами в предыдущем исследовании, которая позволяет определить различные аспекты тезауруса и качество методов его генерации. Проведённый анализ выявил основные достоинства и недостатки различных подходов к построению тезаурусов и выделению семантических связей различных типов, а также позволил определить потенциальные направления будущих исследований.