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Creating Word Class Tagged Corpora
for Northern Sotho by Linguistically
Informed Bootstrapping
Danie J. Prinsloo and Ulrich Heid
To bootstrap tagging resources (tagger lexicon and training corpus) for Northern
Sotho, a tagset and a number of modular and reusable corpus processing tools are
being developed. This article describes the tagset and routines for identifying verbs
and nouns, and for disambiguating closed class items. All of these are based on
morphological and morphosyntactic specificities of Northern Sotho.
1. Introduction
In this paper, we report on ongoing work towards the parallel creation of
computational linguistic resources for Northern Sotho, on the basis of linguistic
knowledge about the language. Northern Sotho is one of the eleven official languages
of South Africa, spoken by about 4.2 million speakers in the northeastern part of the
country. It belongs to the Sotho family of the Bantu languages (S32), (Guthrie 1971).
The three Sotho languages are closely related.
The creation of Natural Language Processing (NLP) resources is part of an effort
towards an infrastructure for corpus linguistics and computational lexicography and
terminology for Northern Sotho, which is seen as an element of a broader action for
the development of Human Language Technology (HLT) and NLP applications for the
South African languages.
Parallel resource creation has been attempted as part of our research and
development agenda in order to speed up the resource building process, in the sense
of rapid prototyping of a part-of-speech (=POS) tagset; a tagger lexicon and (manually
corrected) reference corpus; and a statistical tagger. These constitute the first set of
corpus linguistic tools to be developed (we report on the first three tools here). At the
same time, we intend to verify to what extent ‘traditional’ corpus linguistic methods
and tools (as used for European languages) can be applied to a Bantu language-- an
attempt that, to our knowledge, has not been made before.
Two text corpora are used as input to the study. The first is a 43,000 tokens corpus,
a selection from the Northern Sotho novel Tša ka Mafuri (Matsepe 1974), and the
second is the Pretoria Sepedi Corpus (PSC) of 6 million tokens, a collection of 327
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