Recent work has validated the importance of subword information for word representation learning. Since subwords increase parameter sharing ability in neural models, their value should be even more pronounced in low-data regimes. In this work, we therefore provide a comprehensive analysis focused on the usefulness of subwords for word representation learning in truly low-resource scenarios and for three representative morphological tasks: fine-grained entity typing, morphological tagging, and named entity recognition. We conduct a systematic study that spans several dimensions of comparison: 1) type of data scarcity which can stem from the lack of task-specific training data, or even from the lack of unannotated data required to train word embeddings, or both; 2) language type by working with a sample of 16 typologically diverse languages including some truly low-resource ones (e.g. Rusyn, Buryat, and Zulu); 3) the choice of the subword-informed word representation method. Our main results show that subword-informed models are universally useful across all language types, with large gains over subword-agnostic embeddings. They also suggest that the effective use of subwords largely depends on the language (type) and the task at hand, as well as on the amount of available data for training the embeddings and task-based models, where having sufficient in-task data is a more critical requirement.

本研究探讨了在低资源环境下，子词信息对单词表示学习的有用性以及其在细粒度实体类型、形态标注和命名实体识别等三个典型形态学任务中的应用价值，结果表明，子词信息可以普适地提升单词表示，但其效果受语言类型和任务的影响，同时，训练单词嵌入和基于任务的模型所需的数据越充足，子词信息的效果才会更好。

对于真正低资源语言中形态学任务的子词信息的重要性