{ "paper_id": "2020", "header": { "generated_with": "S2ORC 1.0.0", "date_generated": "2023-01-19T15:01:04.407749Z" }, "title": "Investigating an approach for low resource language dataset creation, curation and classification: Setswana and Sepedi", "authors": [ { "first": "Vukosi", "middle": [], "last": "Marivate", "suffix": "", "affiliation": { "laboratory": "", "institution": "University of Pretoria", "location": {} }, "email": "vukosi.marivate@cs.up.ac.za" }, { "first": "Tshephisho", "middle": [], "last": "Sefara", "suffix": "", "affiliation": { "laboratory": "", "institution": "University of Pretoria", "location": {} }, "email": "tsefara@csir.co.za" }, { "first": "Vongani", "middle": [], "last": "Chabalala", "suffix": "", "affiliation": { "laboratory": "", "institution": "University of Pretoria", "location": {} }, "email": "" }, { "first": "Keamogetswe", "middle": [], "last": "Makhaya", "suffix": "", "affiliation": { "laboratory": "", "institution": "University of Pretoria", "location": {} }, "email": "" }, { "first": "Tumisho", "middle": [], "last": "Mokgonyane", "suffix": "", "affiliation": { "laboratory": "", "institution": "University of Pretoria", "location": {} }, "email": "" }, { "first": "Rethabile", "middle": [], "last": "Mokoena", "suffix": "", "affiliation": { "laboratory": "", "institution": "University of Pretoria", "location": {} }, "email": "" }, { "first": "Abiodun", "middle": [], "last": "Modupe", "suffix": "", "affiliation": { "laboratory": "", "institution": "University of Pretoria", "location": {} }, "email": "" } ], "year": "", "venue": null, "identifiers": {}, "abstract": "The recent advances in Natural Language Processing have only been a boon for well represented languages, negating research in lesser known global languages. This is in part due to the availability of curated data and research resources. One of the current challenges concerning low-resourced languages are clear guidelines on the collection, curation and preparation of datasets for different use-cases. In this work, we take on the task of creating two datasets that are focused on news headlines (i.e short text) for Setswana and Sepedi and the creation of a news topic classification task from these datasets. In this study, we document our work, propose baselines for classification, and investigate an approach on data augmentation better suited to low-resourced languages in order to improve the performance of the classifiers.", "pdf_parse": { "paper_id": "2020", "_pdf_hash": "", "abstract": [ { "text": "The recent advances in Natural Language Processing have only been a boon for well represented languages, negating research in lesser known global languages. This is in part due to the availability of curated data and research resources. One of the current challenges concerning low-resourced languages are clear guidelines on the collection, curation and preparation of datasets for different use-cases. In this work, we take on the task of creating two datasets that are focused on news headlines (i.e short text) for Setswana and Sepedi and the creation of a news topic classification task from these datasets. In this study, we document our work, propose baselines for classification, and investigate an approach on data augmentation better suited to low-resourced languages in order to improve the performance of the classifiers.", "cite_spans": [], "ref_spans": [], "eq_spans": [], "section": "Abstract", "sec_num": null } ], "body_text": [ { "text": "The most pressing issues with regard to low-resource languages are the lack of sufficient language resources, like features related to automation. In this study, we introduce an investigation of a low-resource language that provides automatic formulation and customisation of new capabilities from existing ones. While there are more than six thousand languages spoken globally, the availability of resources among each of those are extraordinarily unbalanced (Nettle, 1998) . For example, if we focus on language resources annotated on the public domain, as of November 2019, AG corpus released about 496, 835 news articles related to the English language from more than 200 sources 1 . Additionally, the Reuters News Dataset (Lewis, 1997) comprise roughly 10, 788 annotated texts from the Reuters financial newswire. Moreover, the New York Times Annotated Corpusholds over 1.8 million articles (Sandhaus, 2008) . Lastly, Google Translate only supports around 100 languages (Johnson et al., 2017) . significant amount of knowledge exists for only a small number of languages, neglecting 17% out of the world's language categories labelled as low-resource, and there are currently no standard annotated tokens in low-resource languages (Strassel and Tracey, 2016) . This in turn, makes it challenging to develop various mechanisms and tools used for Natural Language Processing (NLP). In South Africa, most of the news websites (private and public) are published in English, despite there being 11 official languages (including English). In this paper, we list the premium newspapers by circulation as per the first Quarter of 2019 (Bureau of Circulations, 2019) ( Table 1) . Currently, there is a lack of information surrounding 8 of the 11 official South African languages, with the exception of English, Afrikaans and isiZulu which contain most of the reported datasets. n this work, we aim to provide a general framework for two of the 11 South African languages, to create an annotated linguistic resource for Setswana and Se-1 http://groups.di.unipi.it/\u02dcgulli pedi news headlines. In this study, we applied data sources of the news headlines from the South African Broadcast Corporation (SABC) 2 , their social media streams and a few acoustic news. Unfortunately, at the time of this study, we did not have any direct access to news reports, and hopefully this study can promote collaboration between the national broadcaster and NLP researchers. The rest of the work is organized as follows. Section 2. discusses prior work that has gone into building local corpora in South Africa and how they have been used. Section 3. presents the proposed approach to build a local news corpora and annotating the corpora with categories. From here, we focus on ways to gather data for vectorization and building word embeddings (needing an expanded corpus). We also release and make pre-trained word embeddings for 2 local languages as part of this work (Marivate and Sefara, 2020a) . Section 4. investigate building classification models for the Setswana and Sepedi news and improve those classifiers using a 2 step augmentation approach inspired by work on hierarchical language models (Yu et al., 2019) . Finally, Section 5. concludes and proposes a path forward for this work.", "cite_spans": [ { "start": 460, "end": 474, "text": "(Nettle, 1998)", "ref_id": "BIBREF10" }, { "start": 727, "end": 740, "text": "(Lewis, 1997)", "ref_id": "BIBREF5" }, { "start": 896, "end": 912, "text": "(Sandhaus, 2008)", "ref_id": "BIBREF12" }, { "start": 975, "end": 997, "text": "(Johnson et al., 2017)", "ref_id": "BIBREF3" }, { "start": 1236, "end": 1263, "text": "(Strassel and Tracey, 2016)", "ref_id": "BIBREF14" }, { "start": 2951, "end": 2979, "text": "(Marivate and Sefara, 2020a)", "ref_id": "BIBREF7" }, { "start": 3185, "end": 3202, "text": "(Yu et al., 2019)", "ref_id": "BIBREF17" } ], "ref_spans": [ { "start": 1665, "end": 1673, "text": "Table 1)", "ref_id": "TABREF0" } ], "eq_spans": [], "section": "Introduction", "sec_num": "1." }, { "text": "Creating sizeable language resources for low resource languages is important in improving available data for study (Zoph et al., 2016) and cultural preservation. Focusing on the African continent, we note that there are few annotated datasets that are openly available for Natural Language Processing tasks such as classification. In South Africa, the South African Center for Digital Language Resources (SADiLaR) 3 has worked to curate datasets of local South African languages. There remain gaps such as accessing large corpora and data from sources such as broadcasters and news organizations as they have sizeable catalogs that are yet to make it into the public domain. In this work, we work to fill such a gap by collecting, annotating and training classifier models for news headlines in Setswana and Sepedi. As the data that we do find publicly is still small, we also have to deal with the challenges of Machine Learning on small data. Machine learning systems perform poorly in presence of small training sets due to overfitting. To avoid this problem, data augmentation can be used. The technique is well known in the field of image processing (Cubuk et al., 2019) . Data augmentation refers to the augmentation of the training set with artificial, generated, training examples. This technique is used less frequently in NLP but a number of few studies applied data augmentation.", "cite_spans": [ { "start": 115, "end": 134, "text": "(Zoph et al., 2016)", "ref_id": "BIBREF19" }, { "start": 1155, "end": 1175, "text": "(Cubuk et al., 2019)", "ref_id": "BIBREF2" } ], "ref_spans": [], "eq_spans": [], "section": "Prior Work", "sec_num": "2." }, { "text": "Silfverberg et al. 2017use data augmentation to counteract overfitting where recurrent neural network (RNN) Encoder-Decoder is implemented specifically geared toward a low-resource setting. Authors apply data augmentation by finding words that share word stem for example fizzle and fizzling share fizzl. Then authors replace a stem with another string.", "cite_spans": [], "ref_spans": [], "eq_spans": [], "section": "Prior Work", "sec_num": "2." }, { "text": "Zhang et al. (2015) apply data augmentation by using synonyms as substitute words for the original words. However, Kobayashi (2018) states that synonyms are very limited and the synonym-based augmentation cannot produce numerous different patterns from the original texts. Hence, Kobayashi (2018) proposes contextual data augmentation by replacing words that are predicted by a language model given the context surrounding the original words to be augmented.", "cite_spans": [ { "start": 115, "end": 131, "text": "Kobayashi (2018)", "ref_id": "BIBREF4" }, { "start": 280, "end": 296, "text": "Kobayashi (2018)", "ref_id": "BIBREF4" } ], "ref_spans": [], "eq_spans": [], "section": "Prior Work", "sec_num": "2." }, { "text": "As Wei and Zou (2019) states that these techniques are valid, they are not often used in practice because they have a high cost of implementation relative to performance gain. They propose an easy data augmentation as techniques for boosting performance on text classification tasks. These techniques involve synonym replacement, random insertion, random swap, and random deletion of a word. Authors observed good performance when using fraction of the dataset (%): 1, 5, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, as the data size increases, the accuracy also increases for augmented and original data. Original data obtained highest accuracy of 88.3% at 100% data size while augmented data obtained accuracy of 88.6% at 50% data size.", "cite_spans": [ { "start": 3, "end": 21, "text": "Wei and Zou (2019)", "ref_id": "BIBREF16" }, { "start": 466, "end": 512, "text": "1, 5, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100,", "ref_id": null } ], "ref_spans": [], "eq_spans": [], "section": "Prior Work", "sec_num": "2." }, { "text": "3 www.sadilar.org", "cite_spans": [], "ref_spans": [], "eq_spans": [], "section": "Prior Work", "sec_num": "2." }, { "text": "In this work, we investigate the development of a 2 step text augmentation method in order to be improve classification models for Setswana and Sepedi. To do this we had to first identify a suitable data source. Collect the data, and then annotate the datasets with news categories. After the data is collected and annotated, we then worked to create classification models from the data as is and then use a word embedding and document embedding augmentation approach. In this section discuss how data was collected as well as the approach we use to build classification models.", "cite_spans": [], "ref_spans": [], "eq_spans": [], "section": "Developing news classification models for Setswana and Sepedi", "sec_num": "3." }, { "text": "Before we can train classification models, we first have to collect data for 2 distinct processes. First, we present our collected news dataset as well as its annotation. We then discuss how we collected larger datasets for better vectorisation.", "cite_spans": [], "ref_spans": [], "eq_spans": [], "section": "Data Collection, Cleaning and Annotation", "sec_num": "3.1." }, { "text": "The news data we collected is from the SABC 4 Facebook pages. The SABC is the public broadcaster for South Africa. Specifically, data was collected from Motsweding FM (An SABC Setswana radio station) 5 and Thobela FM (An SABC Sepedi radio station) 6 . We scraped the news headlines that are published as posts on both Facebook pages. We claim no copyright for the content but used the data for research purposes. We summarize the datasets in Table 2 . We visualize the token distributions in Setswana and Sepedi in Figures 1 and 2 respectively. As can be seen, the datasets are relatively small and as such, we have to look at other ways to build vectorizers that can better generalize as the word token diversity would be very low.", "cite_spans": [ { "start": 200, "end": 201, "text": "5", "ref_id": null } ], "ref_spans": [ { "start": 442, "end": 449, "text": "Table 2", "ref_id": "TABREF1" } ], "eq_spans": [], "section": "News data collection and annotation", "sec_num": "3.1.1." }, { "text": "We annotated the datasets by categorizing the news headlines into: Legal, General News,Sports, Other, Politics, Traffic News, Community Activities, Crime, Business and Foreign Affairs. Annotation was done after reading the headlines and coming up with categories that fit both datasets. We show the distribution of the labels in both the Setswana and Sepedi data sets in Figures 3 and 4 (Table 3) . We also make these vectorizers available for other researchers to use. ", "cite_spans": [], "ref_spans": [ { "start": 371, "end": 386, "text": "Figures 3 and 4", "ref_id": "FIGREF2" }, { "start": 387, "end": 396, "text": "(Table 3)", "ref_id": "TABREF3" } ], "eq_spans": [], "section": "News data collection and annotation", "sec_num": "3.1.1." }, { "text": "We explore the use of a few classification algorithms to train news classification models. Specifically we train", "cite_spans": [], "ref_spans": [], "eq_spans": [], "section": "News Classification Models", "sec_num": "3.2." }, { "text": "\u2022 Logistic Regression,", "cite_spans": [], "ref_spans": [], "eq_spans": [], "section": "News Classification Models", "sec_num": "3.2." }, { "text": "\u2022 Support Vector Classification,", "cite_spans": [], "ref_spans": [], "eq_spans": [], "section": "News Classification Models", "sec_num": "3.2." }, { "text": "\u2022 XGBoost, and", "cite_spans": [], "ref_spans": [], "eq_spans": [], "section": "News Classification Models", "sec_num": "3.2." }, { "text": "\u2022 MLP Neural Network.", "cite_spans": [], "ref_spans": [], "eq_spans": [], "section": "News Classification Models", "sec_num": "3.2." }, { "text": "To deal with the challenge of having a small amount of data on short text, we use data augmentation methods, specifically a word embedding based augmentation (Wang and Yang, 2015) , approach that has been shown to work well on short text (Marivate and Sefara, 2019) . We use this approach since we are not able to use other augmentation methods such as synonym based (requires developed Wordnet Synsets (Kobayashi, 2018) ), language models (larger corpora needed train) and back-translation (not readily available for South African languages). We develop and present the use of both word and document embeddings (as an augmentation quality check) inspired by a hierarchical approach to augmentation (Yu et al., 2019) .", "cite_spans": [ { "start": 158, "end": 179, "text": "(Wang and Yang, 2015)", "ref_id": "BIBREF15" }, { "start": 238, "end": 265, "text": "(Marivate and Sefara, 2019)", "ref_id": "BIBREF6" }, { "start": 403, "end": 420, "text": "(Kobayashi, 2018)", "ref_id": "BIBREF4" }, { "start": 699, "end": 716, "text": "(Yu et al., 2019)", "ref_id": "BIBREF17" } ], "ref_spans": [], "eq_spans": [], "section": "News Classification Models", "sec_num": "3.2." }, { "text": "This Section presents the experiments and results. As this is still work in progress, we present some avenues explored in both training classifiers and evaluating them for the task of news headline classification for Setswana and Sepedi.", "cite_spans": [], "ref_spans": [], "eq_spans": [], "section": "Experiments and Results", "sec_num": "4." }, { "text": "For each classification problem, we perform 5 fold cross validation. For the bag-of-words and TFIDF vectorizers, we use a maximum token size of 20,000. For word embeddings and language embeddings we use size 50. All vectorizers were trained on the large corpora presented earlier.", "cite_spans": [], "ref_spans": [], "eq_spans": [], "section": "Experimental Setup", "sec_num": "4.1." }, { "text": "We run the baseline experiments with the original data using 5-fold cross validation. We show the performance (in terms of weighted F1 score) in the Figures 5 and 6 . We show the baseline results as orig. For both the Bag-of-Words (TF) and TFIDF, the MLP performs very well comparatively to the other methods. In general the TFIDF performs better. ", "cite_spans": [], "ref_spans": [ { "start": 149, "end": 164, "text": "Figures 5 and 6", "ref_id": "FIGREF4" } ], "eq_spans": [], "section": "Baseline Experiments", "sec_num": "4.1.1." }, { "text": "We applied augmentation in different ways. First for Sepedi and Setswana word embeddings (word2vec), we use word embedding-based augmentation. We augment each dataset 20 times on the training data while the validation data is left intact so as to be comparable to the earlier baselines. We show the effect of augmentation in Figures 5 and 6 (performance labeled with aug). The contextual, word2vec based, word augmentation improves the performance of most of the classifiers. If we now introduce a quality check using doc2vec (Algorithm 1) we also notice the impact on the performance for Sepedi (Figure 6 aug qual ) . We were not able to complete experiments with Setswana for the contextual augmentation with a quality check, but will continue working to better under stand the impact of such an algorithm in general. For example, it remains further work to investigate the effects of different similarity thresholds for the algorithm on the overall performance, how such an algorithm works on highly resourced languages vs low resourced languages, how we can make the algorithm efficient etc. It also interesting to look at how performance of classifiers that were only trained with word2vec features would fair. Deep neural networks are not used in this current work and as such we did not use recurrent neural networks, but we can create sentence features from -word2vec by either using: the mean of all word vectors in a sentence, the median of all word vectors in a sentence or the concatenated power means (R\u00fcckl\u00e9 et al., 2018) . We show the performance of using this approach with the classifiers used for Bag of Words and TFIDF earlier in Figure 7 . The performance for this approach is slightly worse with Algorithm 1: Contextual (Word2vec-based) augmentation algorithm with a doc2vec quality check Input: s: a sentence, run: maximum number of attempts at augmentation Output:\u015d a sentence with words replaced 1 def Augment(s,run): the best results for Sepedi news headline classification being with XGBoost on the augmented data. We hope to improve this performance using word2vec feature vectors using recurrent neural networks but currently are of the view that increasing the corpora sizes and the diversity of corpora for the pre-trained word embeddings may yield even better results. Finally, we show the confusion matrix of the best model in Sepedi on a test set in Figure 8 . The classifier categorizes General News, Politics and Legal news headlines best. For others there is more error. A larger news headline dataset is required and classification performance will also need to be compared to models trained on full news data (with the article body). For the Setswana classifiers, the confusion matrix shows that the data skew results in models that mostly can categorize between categories General News and Other. We need to look at re-sampling techniques to improve this performance as well as increasing the initial dataset size.", "cite_spans": [ { "start": 1514, "end": 1535, "text": "(R\u00fcckl\u00e9 et al., 2018)", "ref_id": "BIBREF11" } ], "ref_spans": [ { "start": 596, "end": 616, "text": "(Figure 6 aug qual )", "ref_id": "FIGREF5" }, { "start": 1649, "end": 1657, "text": "Figure 7", "ref_id": "FIGREF7" }, { "start": 2383, "end": 2391, "text": "Figure 8", "ref_id": "FIGREF8" } ], "eq_spans": [], "section": "Augmentation", "sec_num": "4.1.2." }, { "text": "2 Let #\u00bb V", "cite_spans": [], "ref_spans": [], "eq_spans": [], "section": "Augmentation", "sec_num": "4.1.2." }, { "text": "This work introduced the collection and annotation of Setswana and Sepedi news headline data. It remains a challenge that in South Africa, 9 of the 11 official languages have little data such as this that is available to researchers in order to build downstream models that can be used in different applications. Through this work we hope to provide an example of what may be possible even when we have a limited annotated dataset. We exploit the availability of other free text data in Setswana and Sepedi in order to build pre-trained vectorizers for the languages (which are released as part of this work) and then train classification models for news categories. It remains future work to collect more local language news headlines and text to train more models. We have identified other government news sources that can be used. On training embedding models with the data we have collected, further studies are needed to look at how augmentation using the embedding models improve the quality of augmentation.", "cite_spans": [], "ref_spans": [], "eq_spans": [], "section": "Conclusion and Future Work", "sec_num": "5." }, { "text": "Bojanowski, P., Grave, E., Joulin, A., and Mikolov, T. (2017) . Enriching word vectors with subword informa-", "cite_spans": [ { "start": 39, "end": 61, "text": "and Mikolov, T. 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guages
PaperLanguage Circulation
Sunday TimesEnglish260132
Soccer LadumaEnglish252041
Daily SunEnglish141187
RapportAfrikaans 113636
IsolezweisiZulu86342
SowetanEnglish70120
Isolezwe ngeSontoisiZulu65489
Isolezwe ngoMgqibelo isiZulu64676
SonAfrikaans 62842
" }, "TABREF1": { "html": null, "num": null, "type_str": "table", "text": "", "content": "
: News Data Sets
Setswana Sepedi
Corpus Size (headlines)219491
Number of Tokens (words) 15613018
" }, "TABREF2": { "html": null, "num": null, "type_str": "table", "text": "TrafficTona ya toka Michael Masutha,ore bahlankedi ba kgoro ya ditirelo tsa tshokollo ya bagolegwa bao ba tateditswego dithieeletsong tsa khomisene ya go nyakisisa mabarebare a go gogwa ga mmuso ka nko,ba swanetse go hlalosa gore ke ka lebaka la eng ba sa swanelwa go fegwa mesomong Legal The full dataset is made available online (Marivate and Sefara, 2020b) for further research use and improvements to the annotation 7 . As previously discussed, we used larger corpora to create language vectorizers for downstream NLP tasks. We discuss this next.", "content": "
Setswana News Title Categories
General News
Legal
Other
Politics
CategoryCrime Foreign Affairs
Traffic News
Sports
Community Activities
Business
010203040 Frequency506070
" }, "TABREF3": { "html": null, "num": null, "type_str": "table", "text": "", "content": "
: Vectorizer Corpora Sizes in number of lines (num-
ber of tokens)
SourceSetswanaSepedi
Wikipedia478(21924) 8300(10190) 9
JW300 10874464(70251)618275(53004)
Bible31102(42233)29723(38709)
Constitution 11 7077(3940)6564(3819)
SADILAR 1233144(61766)67036(87838)
Total946264(152027) 721977(149355)
" } } } }