Toward a knowledge-to-text controlled natural language of isiZulu

The language isiZulu belongs to the Nguni group of languages, which also include isiXhosa, isiNdebele and siSwati. Of the four Nguni languages, isiZulu is the most dominant language in South Africa, which is spoken by 22.7% of the country’s 51.8 million population. However, isiZulu (and even more so the other Nguni languages) still remains an under-resourced language for software applications. In this article we focus on controlled natural languages for structured knowledge-to-text viewed from a potential utility for verbalising business rules and OWL ontologies. IsiZulu grammar—and by extension, all Bantu languages—shows that a template-based approach is infeasible. This is due to, mainly, the noun class system, the agglutination and verb conjugation with concords for each noun class. We present verbalisation patterns for existential and universal quantification, taxonomic subsumption, axioms with simple properties, and basic cases of negation. Based on the preliminary user assessment of the patterns, selected ones are refined into algorithms for verbalisation to generate correct isiZulu sentences, which have been evaluated.