A conversation is based on internal knowledge that the participants already know or external knowledge that they have gained during the conversation. A chatbot that communicates with humans by using its internal and external knowledge is called a knowledge-grounded chatbot. Although previous studies on knowledge-grounded chatbots have achieved reasonable performance, they may still generate unsuitable responses that are not associated with the given knowledge. To address this problem, we propose a knowledge-grounded chatbot model that effectively reflects the dialogue context and given knowledge by using well-designed attention mechanisms. The proposed model uses three kinds of attention: Query-context attention, query-knowledge attention, and context-knowledge attention. In our experiments with the Wizard-of-Wikipedia dataset, the proposed model showed better performances than the state-of-the-art model in a variety of measures.

Document-grounded conversation (DGC) is a natural language generation task to generate fluent and informative responses by leveraging dialogue history and document(s). Recently, DGCs have focused on fine-tuning using pretrained language models. However, these approaches have a problem in that they must leverage the background knowledge under capacity constraints. For example, the maximum length of the input is limited to 512 or 1024 tokens. This problem is fatal in DGC because most documents are longer than the maximum input length. To address this problem, we propose a document-grounded generative model using a knowledge graph. The proposed model converts knowledge sentences extracted from the given document(s) into knowledge graphs and fine-tunes the pretrained model using the graph. We validated the effectiveness of the proposed model using a comparative experiment on the well-known Wizard-of-Wikipedia dataset. The proposed model outperformed the previous state-of-the-art model in our experiments on the Doc2dial dataset.