Development of Stemming Algorithm for Wolaytta Text

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Addis Ababa University


This study describes the design of a stemming algorithm for Wolaytta language. To give a solid background for the thesis, literature on conflation in general and stemming algorithms in particular were reviewed. Since it is the nature and characteristics of suffixation that guide the development of steamer, the Wolaytta language morphology was studied and described in order to model the language and develop an automatic procedure for conflation. The inflectional and derivational morphologies of the language are discussed. It is indicated that suffixation is the main word formation process in Wordplay language. It is also attempted to show that the language is morphological complex and uses extensive concatenation of suffixes The result of the study is a prototype context sensitive iterative stemmer for Wolaytta language. Error counting technique was employed to evaluate the performance of this stemmer. The stemmer was trained on 3537 words (80% of the sample text) and the improved version reveals an accuracy of 90.6% on the training set. The number of over stemmed and understeml11ed words on the training set were 8.6% (304 words) and 0.8% (28 words) respectively. When the stemmer rW1S on the unseen sample of 884 words (20% of the sample text), it performed with an accuracy of 86.9%. The percentage of endorser recorded as under stunned and over stemmed on this unseen (test set) were 9% and 4.1 %, respectively. Moreover, a dictionary reduction of 38 .92% was attained on the test set. The major sources of errors are also reported with possible recommendations to further improve the performance of the stemmer and also for further research.



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