Enriching text with tone marks: An application to Kinyarwanda language

The absence of tone marks in text can be considered an instance of defective writing. Yet most writing systems of tone languages in Africa do not mark tone. This adds to ambiguity, which must be resolved on the basis of the context. Using tone-marked lexicons and tone rules the ambiguity can be resolved. This paper deals with a further problem, i.e. how to insert tone marks into a text without tone marking. Such a tool is needed in text-to-speech applications, and whenever a text needs to be provided with tone marks. Three approaches are briefly discussed, and one of them is selected for discussion, implementation and demonstration. The implementation makes use of Finite State Methods in analysis, Constraint Grammar in disambiguation, and regular expressions in writing tone rules. The system was implemented using Kinyarwanda verb morphology for testing and demonstration. It is assumed that the approach is suitable especially for tone languages that have lexical and grammatical tone.