Coreferent Pairs Detection in Ukrainian Texts Using a Convolutional Neural Network

Abstract

The detection of coreferent pairs within a text is one of the basic tasks in the area of natural language processing (NLP). The state‑ of‑ the‑ art methods of coreference resolution are based on machine learning algorithms. The key idea of the methods is to detect certain regularities between the semantic or grammatical features of text entities. In the paper, the comparative analysis of current methods of coreference resolution in English and Ukrainian texts has been performed. The key disadvantage of many methods consists in the interpretation of coreference resolution as a classification problem. The result of coreferent pairs detection is the set of groups in which elements refer to a common entity. Therefore it is advisable to consider the coreference resolution as a clusterization task. The method of coreference resolution using the set of filtering sieves and a convolutional neural network has been suggested. The set of filtering sieves to find candidates for coreferent pairs formation has been implemented. The training process of a multichannel convolutional neural network on a marked Ukrainian corpus has been performed. The usage of a multichannel structure allows analyzing of the different components of text units: semantic, lexical, and grammatical features of words and sentences. Furthermore, it is possible to process input data with unfixed size (words or sentences of a text) using a convolutional layer. The output result of the method is the set of clusters. In order to form clusters, it is necessary to take into account the previous steps of the model’s workflow. Nevertheless, such an approach contradicts the traditional methodology of machine learning. Thus, the training process of the network has been performed using the SEARN algorithm that allows the solving of tasks with unfixed output structures using a classifier model. An experimental examination of the method on the corpus of Ukrainian news has been performed. In order to estimate the accuracy of the method the corresponding common metrics for clusterization tasks have been calculated. The results obtained can indicate that the suggested method can be used to find coreferent pairs within Ukrainian texts. The method can be also easily adapted and applied to other natural languages.

Silver Data for Coreference Resolution in Ukrainian: Translation, Alignment, and Projection

“…The author does not report accuracy scores for this part of the system. Pogorilyy and Kramov (2019) attempt to create a coreference resolution system for Ukrainian using a convolutional neural network. Following Clark and Manning (2016), coreference resolution is presented as a clustering task.…”

“…For creating the clusters, the system proposed in Pogorilyy and Kramov (2019) uses a rule-based filtering sieves module and a multichannel CNN module. The rules are mostly based on direct string comparison with regular expressions, although some of them incorporate dictionaries of entity names scraped from Wikipedia.…”