Using Deep-Q Network to Select Candidates from N-best Speech Recognition Hypotheses for Enhancing Dialogue State Tracking

摘要

Most state-of-the-art dialogue state tracking (DST) methods infer the dialogue state based on ground-truth transcriptions of utterances. In real-world situations, utterances are transcribed by automatic speech recognition (ASR) systems, which output the n-best candidate transcriptions (hypotheses). In certain noisy environments, the best transcription is often imperfect, severely influencing DST accuracy and possibly causing the dialogue system to stall or loop. The missed or misrecognized words can often be found in the runner-up candidate transcriptions from 2 to n, which could be used to improve accuracy of DST. However, looking beyond the top-ranked ASR results poses a dilemma: going too far may introduce noise, while not going far enough may not uncover any useful information. In this paper, we propose a novel approach to automatically determine the optimal time to stop reexamining runner-up ASR transcriptions based on deep reinforcement learning. Our method outperforms the baseline system, which uses only the top-1 ASR result, by 3.1%. Then, we select the dialogue rounds with the top-10 largest word error rate (WER), our method can improve DST accuracy by 15.4%, which is five times the overall improvement rate (3.1%). This improvement was expected because our proposed method is able to select informative ASR results at any rank.