An important yet rarely tackled problem in dialogue state tracking (DST) is scalability for dynamic ontology (e.g., movie, restaurant) and unseen slot values. We focus on a specific condition, where the ontology is unknown to the state tracker, but the target slot value (except for none and dontcare), possibly unseen during training, can be found as word segment in the dialogue context. Prior approaches often rely on candidate generation from n-gram enumeration or slot tagger outputs, which can be inefficient or suffer from error propagation. We propose BERT-DST, an end-to-end dialogue state tracker which directly extracts slot values from the dialogue context. We use BERT as dialogue context encoder whose contextualized language representations are suitable for scalable DST to identify slot values from their semantic context. Furthermore, we employ encoder parameter sharing across all slots with two advantages: (1) Number of parameters does not grow linearly with the ontology. (2) Language representation knowledge can be transferred among slots. Empirical evaluation shows BERT-DST with cross-slot parameter sharing outperforms prior work on the benchmark scalable DST datasets Sim-M and Sim-R, and achieves competitive performance on the standard DSTC2 and WOZ 2.0 datasets.

本研究提出了BERT-DST，一种基于BERT的端到端的对话状态跟踪器，它可以从对话上下文中直接提取槽值，并采用所有槽的编码参数共享的方法，实现了可扩展的对话状态跟踪。实证评估表明，BERT-DST在可扩展的数据集Sim-M和Sim-R上优于之前的方法，在标准数据集DSTC2和WOZ 2.0上取得了具有竞争力的性能。

BERT-DST: 基于双向变换器编码器表示的可扩展端到端对话状态跟踪