Lexicon-injected Semantic Parsing for Task-Oriented Dialog

Recently, semantic parsing using hierarchical representations for dialog systems has captured substantial attention. Task-Oriented Parse (TOP), a tree representation with intents and slots as labels of nested tree nodes, has been proposed for parsing user utterances. Previous TOP parsing methods are limited on leveraging lexicon resources, which are often used to guide the real dialog system. To mitigate this issue, we first propose a novel span-splitting representation for span-based parser that outperforms existing methods. Then we present a novel lexicon-injected semantic parser, which collects slot labels of tree representation as a lexicon, and injects lexical features to the span representation of parser. An additional slot disambiguation technique is involved to remove inappropriate span match occurrences from the lexicon. Experiments show that our best parser produces a new state-of-the-art result (87.62%) on the TOP dataset, and also confirm the effectiveness of our proposed lexicon-injected parser and slot disambiguation model.