Bridging Gaps in Natural Language Processing for Yor\`ub\'a: A Systematic Review of a Decade of Progress and Prospects

TL;DR

This systematic review analyzes a decade of NLP research for Yorùbá, highlighting challenges like resource scarcity and linguistic complexity, and emphasizing the need for more annotated data, models, and inclusive techniques to advance NLP for this under-resourced language.

Contribution

The paper provides a comprehensive analysis of NLP studies for Yorùbá from 2014 to 2024, identifying key challenges, resources, and research gaps to guide future efforts.

Findings

Scarcity of annotated corpora and pre-trained models

Linguistic challenges like tonal complexity and diacritic dependency

Growing resources but socio-cultural constraints limit progress

Abstract

Natural Language Processing (NLP) is becoming a dominant subset of artificial intelligence as the need to help machines understand human language looks indispensable. Several NLP applications are ubiquitous, partly due to the myriad of datasets being churned out daily through mediums like social networking sites. However, the growing development has not been evident in most African languages due to the persisting resource limitations, among other issues. Yor\`ub\'a language, a tonal and morphologically rich African language, suffers a similar fate, resulting in limited NLP usage. To encourage further research towards improving this situation, this systematic literature review aims to comprehensively analyse studies addressing NLP development for Yor\`ub\'a, identifying challenges, resources, techniques, and applications. A well-defined search string from a structured protocol was employed to search, select, and analyse 105 primary studies between 2014 and 2024 from reputable databases. The review highlights the scarcity of annotated corpora, the limited availability of pre-trained language models, and linguistic challenges like tonal complexity and diacritic dependency as significant obstacles. It also revealed the prominent techniques, including rule-based methods, among others. The findings reveal a growing body of multilingual and monolingual resources, even though the field is constrained by socio-cultural factors such as code-switching and the desertion of language for digital usage. This review synthesises existing research, providing a foundation for advancing NLP for Yor\`ub\'a and in African languages generally. It aims to guide future research by identifying gaps and opportunities, thereby contributing to the broader inclusion of Yor\`ub\'a and other under-resourced African languages in global NLP advancements.