Designing Dictionary Based Spelling Checker for Afaan Oromoo

Abstract

The focus of this thesis work is to design dictionary based spelling checker for Afaan Oromoo language. We proposed a dictionary lookup and n-gram approach to detect the misspelled word(s) and provide the correction suggestions. Accordingly, we built a dictionary from different domains consisting of correctly spelled words. The prepared dictionary is used as a point of reference in error detection and correction. The input word from the user would be cross-checked with the already built dictionary and we have employed a dictionary lookup approach in doing so. If the user input word is found in the dictionary, then the spelling checker considers it as correctly spelled. Otherwise, the word would be detected as misspelled and the next task will be generating the possible corrections for that particular word. To do so, we have used n-gram approach to generate those words having a shared or common bigrams as suggestions from the dictionary with respect to the wrongly spelled word(s). The generated suggestions will be ranked in accordance with their similarity relative to the invalid word(s) so that the most likely correction word to replace the wrongly spelled word would be at the top of the suggested list of words. To make this happen, we have employed the Dice‟s coefficient similarity measure. Accordingly, the candidate word with the highest dice‟s score would be the most likely to substitute the misspelled word. For evaluating the performance of the spelling checker, we have used precision and recall metrics as performance measurements. Consequently, a test dictionary of 3000 words collected from different domains of Afaan Oromoo language is used to test the capability of the spelling checker in error detection and providing corrections for those detected words. Accordingly, the results from evaluation reveal that the designed system scored a precision of 100% and 83.33% of recall. Additionally, we have also conducted an experiment to demonstrate the possible factors that could affect the performance of the designed spelling checker under selected three circumstances.