Rigardt Pretorius

Phonetically grounded phonology and sound change: The case of Tswana labial plosives

Abstract A widely held assumption in phonology is that phonology should be phonetically grounded. Under a strict version of this view, productive phonological processes that counter phonetic naturalness should not be possible. Traditional grammars of Tswana describe it as having a productive process of post-nasal devoicing of voiced plosives (/mb/→[mp]), counter to phonetic expectations. The vocal fold settings during the nasal should promote, not inhibit, voicing in a following consonant. Leakage through the velic valve during the initial part of the post-nasal oral closure should inhibit buildup of intra-oral air pressure and hence promote voicing. The unexpectedness of the Tswana pattern leads to questioning the accuracy and reliability of the traditional descriptions of this language. In this paper, we report an acoustic study of 12 Tswana speakers, showing that there is evidence that at least some speakers have an active, productive process of post-nasal devoicing. However, our data also show evidence that this phonetically unnatural system is unstable, and is in fact in the process of changing towards a more natural system. We consider the relevance of these results for views about the relationship between phonetics and phonology, and for theories of language change.

Automatic lemmatization in Setswana: towards a prototype

Development of human language technologies for the indigenous South African languages is currently being undertaken in various projects across South Africa. In one such project a lemmatizer for Setswana is being developed, and this article reports on work towards the development of a first prototype. A prerequisite of lemmatization is to determine what the output of a lemmatizer for a specific language should be (i.e. what should be considered a lemma in that language). Consequently, the concept of a lemma as it should be understood in the context of Setswana lemmatization is defined, and it is indicated that only nouns and verbs really pose challenges for the lemmatization of Setswana. The computational approach taken in this research, and the implementation applied, which use FSA 6, are described at length. Preliminary results indicate that the rules for nouns and verbs are rather accurate, with precision scores of 93–94% obtained in a small, contained experiment. The article concludes with a discussion of future work.

A finite-state morphological analysis of Tswana nouns

This article describes the progress made in developing a broad-coverage computational morphological analyser for Tswana, an agglutinative disjunctively written indigenous South African language. Two central questions are addressed, viz. what is essential in order to build a broad-coverage computational morphological analyser/generator and how do we go about building this software application? In answer to the first question, a precise linguistic description is required of the linguistic phenomena mechanisms governing the morphology of the relevant natural language, in this case Tswana, the accurate modelling and implementation of these morphological phenomena and, ideally speaking, a complete list of all and only the valid roots and stems in Tswana. The answer to the second question lies within the realm of the discipline of software engineering and its methodologies. The article discusses the development of a morphological analyser with respect to the appropriate life cycle model, tools and testing procedures; Tswana noun morphology, in particular, the relevant morphotactics and morphophonological alternation rules; their modelling and implementation: preliminary results; testing procedures and future work.

A finite state approach to setswana verb morphology

Setswana is characterised by a disjunctive orthography according to which verbal prefixal morphemes are usually written disjunctively, while suffixal morphemes to the verb root follow a conjunctive writing style. This article specifically focusses on a finite-state approach to Setswana verb morphology and the challenges of the disjunctive orthography used for prefixes.

The sequence and productivity of Setswana verbal suffixes

Setswana is an agglutinative language with a rich verbal morphology, allowing for an elaborate system of verbal inflection. Until now, research on Setswana verbal morphology has largely been based on qualitative methods. This paper discusses the frequency of use and the sequencing of Setswana verbal suffixes, based on statistics extracted from the 67,284 orthographic-unit, annotated NCHLT Setswana corpus which includes 9,146 verbs. On this quantitative basis, the relationship between productivity/frequency and the position/slot of Setswana verbal suffixes is investigated. In addition, the relationship between the frequency and position of these same Setswana verbal suffixes and their inflectional or derivational nature is also considered. The data is subsequently used to evaluate and comment on existing descriptive grammars of Setswana.