TS-DST: A Two-Stage Framework for Schema-Guided Dialogue State Tracking with Selected Dialogue History

The task-oriented dialogue systems aim to assist the users in completing specific tasks through natural language dialogue. Recently, word-level dialogue state tracking (DST) has become a core component of task-oriented dialogue systems. In this paper, we study the word-level DST task at the 8th dialogue system technology challenge (DSTC8), namely schema-guided dialogue state tracking, which focuses on cross-domain dialogue state tracking and zero-shot generalization to new services. Many approaches have been proposed to exploit the schema description for dialogue modeling, especially on unseen services. Despite their success, existing methods still suffer from two weaknesses: (1) the current methods do not fully exploit the dialogue history, which makes it difficult to solve the slot carryover problem from the multi-domain dialogues; (2) the current method treats the task as four independent sub tasks without considering the relevance of the subtasks. To address these issues, we propose a novel two-stage framework for schema-guided dialogue state tracking with selected dialogue history (TS-DST). Specifically, to solve the first issue, we propose a novel utterance selection module to select the most related previous utterances from the dialogue history by considering the specific schema element. To solve the second issue, we propose a two-stage framework to solve the four subtasks. Experiments conducted on the SGD dataset show that our method achieves new state-of-the-art performance. We also conduct ablation studies to demonstrate the effectiveness of the utterance selection module and the two-stage strategy.