Learning better lexical properties for recurrent OOV words

Out-of-vocabulary (OOV) words can appear more than once in a conversation or over a period of time. Such multiple instances of the same OOV word provide valuable information for learning the lexical properties of the word. Therefore, we investigated how to estimate better pronunciation, spelling and part-of-speech (POS) label for recurrent OOV words. We first identified recurrent OOV words from the output of a hybrid decoder by applying a bottom-up clustering approach. Then, multiple instances of the same OOV word were used simultaneously to learn properties of the OOV word. The experimental results showed that the bottom-up clustering approach is very effective at detecting the recurrence of OOV words. Furthermore, by using evidence from multiple instances of the same word, the pronunciation accuracy, recovery rate and POS label accuracy of recurrent OOV words can be substantially improved.