Evaluating the Sesotho rule-based syllabification system on Sepedi and Setswana words (2023)

Abstract: The purpose of this article is to demonstrate that the recently developed automated rule-based syllabification system for Sesotho can be used broadly across the officially recognised South African Sotho-Tswana language group encompassing Sepedi, Sesotho and Setswana. We evaluate the automatic syllabification system on 400 words comprising 100 most frequently used words and 100 least-used words in Sepedi and Setswana as evident in the Autshumato corpus publicly available online. It is found that the Sesotho rule-based syllabification system can be used to correctly identify vowel-only syllables, consonant-vowel syllables and consonant-only syllables in Sepedi and Setswana. Among other findings, it has been demonstrated that words with diacritics as in the case of Sepedi are correctly broken down into syllables. We make two main recommendations. First, the rules for syllabification should be updated so that Sepedi diacritics are accommodated. Second, the syllabification system should be updated so that it reflects the broader Sotho-Tswana language group instead of being limited to Sesotho. Further research is needed to ascertain whether the complex consonant [ny] behaves similarly in all three officially recognised Sotho-Tswana languages and evaluate the need for a specific rule for the [ny] digraph.

## introduction this article presents an evaluation of the sesotho rule-based syllabification system for use in sepedi and setswana written texts. the republic of south africa recognises eleven official languages, namely, afrikaans, english, isindebele, isixhosa, isizulu, siswati, sepedi, sesotho, setswana, tshivenda, and xitsonga @xcite . of these eleven languages, afrikaans and english are often identified as germanic languages @xcite . even so, some argue that afrikaans is an african language as it is spoken in africa even though it is a variant of dutch @xcite . isindebele, isixhosa, isizulu and isiswati are classified under the nguni language group. sepedi [also referred to as northern sotho @xcite ], sesotho [also referred to as southern sotho @xcite ], and setswana [sometimes referred to as western sotho @xcite ] are grouped under the sotho-tswana language group. these sotho-tswana languages have many variations within themselves. even so, they are mutually intelligible in that the speakers of these languages can understand each other without difficulty @xcite . the national language bodies, under the auspices of the pan south african language board (pansalb) have dictated three different orthographies for these languages. pansalb develops rules and standards for spelling and orthography for the proper functioning of all official languages foot_0 . according to the 2011 census foot_1 , there were at least 4 618 577 sepedi first language speakers, 3 849 562 sesotho first language speakers and 4 067 248 setswana first language speakers in south africa alone @xcite . sesotho is also an official language in lesotho and zimbabwe. setswana is also one of the official languages of botswana. the south african human language technologies surveys indicate that there is a paucity of research in syllabification systems for the indigenous languages of south africa @xcite @xcite . as far as we are aware, sesotho is presently the only south african indigenous language to have a publicly accessible rule-based syllabification system. even so, according to @xcite , there are two systems for syllabification in sesotho. the machine learning t e x-based pattern-ing system relies on gold-standard corpora with exemplified syllable annotations. the sesotho t e xbased syllabification system used a gold standard list of words and their syllables 3 . unfortunately, we are not aware of similar lists for sepedi and setswana. as such, we cannot evaluate this machine learning system in this article. this article aims to demonstrate the applicability of the sesotho rule-based system in identifying syllables in the wider south african sotho-tswana language group. we provide a very brief background to orthographies of south african languages and expected syllable types in sepedi and setswana in section 2. we then describe our method of data collection in section 3. finally, we discuss our findings in section 4 and end with a discussion in section 5. ## results this section presents the results of the syllabification process. both the 100 most used words and the 100 least used words from the autshumato corpora for sepedi and setswana are presented. stop words were not considered for any of the four lists. the v-syllables structure was observed for monosyllabic vowel-only words such as a, e, e, o and o. furthermore, we observed v-syllables at the wordinitial position in words such as ile [i-le-] 'went', the word-medial position in words such as taolo [ta-o-lo-] 'control', and the word-final position in words such as tee [te-e-] 'only'. we did not observe any erroneous identification of v-syllables. at least four cv-syllable types are present on the list. first, the one-consonant-one-vowel structure was observed in words such as kudu [ku-du-] 'a lot' which was correctly broken into two syllables. second, the cwv syllable structure was evident in words such as bohlokwa [bo-hlo-kwa-] 'important' which was broken into three syllables. third, the ccv structure was evident in words such as tšeo [tše-o-] 'those'. fourth, the ccwv structure was evident in words such as ngwaga [ngwa-ga-] 'year' which was broken into two syllables. fifth, the cccv structure was observed in words such as setšhaba [se-tšha-ba-] 'nation' which was broken into three syllables. unfortunately, there were no instances of cccwv syllable structures on the list. furthermore, our list of frequently used words was limited in that it did not reflect all possible consonant-only syllable types. even so, we were able to investigate the behaviour of the syllabic m and n nasal consonants. for instance, we find words such as mmušo [m-mu-šo-] 'government' and nngwe [n-ngwe-] 'one' which were correctly broken into syllables. ## discussion as stated earlier in this article, the sotho-tswana languages are mutually intelligible to a great extent. even though some vocabulary choices may be ambiguous, the ambiguity does not affect syllable breaks. this article set out to evaluate the sesotho rule-based syllabification system on both sepedi and setswana words. we used the autshumato machine translation corpora for both sepedi and setswana. the texts were translated from english texts as a pivot language. as a result, they contain somewhat similar information. the v-syllable structures showed consistently correct syllable placement in both sepedi and setswana. all v-syllable structures argued by @xcite were identified for both sepedi and setswana. all word-initial, word-medial, and wordfinal v-syllable structures were correctly identified. this consistency in the accuracy of the syllable breaks indicates that the current sesotho syllabifi-cation system is ideal for identifying v-syllables in both sepedi and setswana. unfortunately, singleletter words cannot be broken down into syllables. even so, no unexpected outputs were observed for single-letter vowel-only words. the syllabification system inserted consistently correct syllable breaks in words containing the m and n syllabic consonants on both sepedi and setswana texts. unfortunately, the n could only be identified at the word-end position in sepedi. as such, we were not able to observe its behaviour when it appears at word-initial and word-medial positions. even so, the word-medial n syllable was correctly identified in the setswana list. furthermore, the sepedi list did not contain any instances of the l syllable. however, it was observed in the setswana list. as a result, we can safely assume that the current syllabification system can insert correct syllable boundaries for the l consonant even in sepedi as the l syllable behaves similarly in all three sotho-tswana languages. the unexpected structure of the dmi syllable highlights a need for clear rules governing the behaviour of nasal consonants that follow other consonants. to this point, the rules are only descriptive when the nasal consonant comes before the other consonants. it might be interesting to also investigate this in future studies. although the system attempted to identify syllable boundaries in non-sotho-tswana words, that is english words, the discord between the rules as implemented in the syllabification system and the structure of the orthography of english words could not be ignored. all expected syllable boundaries in the correctly spelt words in setswana were successfully identified by the syllabification system. we however missed an instance of consecutive r syllable in both the sepedi and the setswana lists. it would have been interesting to analyse actual setswana words with such instances. nonetheless, we noticed the absence of a syllable break between consecutive r letters in the non-setswana examples. this finding confirms our initial assumption that the current sesotho syllabification system does not identify the r syllabic consonants. we also noticed inconsistencies in the spelling of words like aaforika and aaferika 'africa' in the setswana list of one hundred rarest used words. both words were justifiably broken into syllables according to the given incorrect spelling, see the syllabification system's inability to recognise diacritics such as those used in sepedi proved unproblematic for our selected words. that is, sepedi words with diacritics were correctly broken into syllables. even so, we are not aware of all possible placements of letters with accents in the written sepedi words. as a caution, we recommend that the update to the syllabification system include letters with diacritics. overall, we recommend that the sesotho rulebased syllabification be updated to cover all three standardised sotho-tswana languages. we also recommend that diacritics be included and specifically handled in the recommended sotho-tswana syllabification system. equally important, we recommend that updated rules should also cover specific rules for handling the sepedi and setswana r syllable.