The problem of answering questions using knowledge from pre-trained language
models (LMs) and knowledge graphs (KGs) presents two challenges: given a QA
context (question and answer choice), methods need to (i) identify relevant
knowledge from large KGs, and (ii) perform joint reasoning over the QA context
and KG. In this work, we propose a new model, QA-GNN, which addresses the above
challenges through two key innovations: (i) relevance scoring, where we use LMs
to estimate the importance of KG nodes relative to the given QA context, and
(ii) joint reasoning, where we connect the QA context and KG to form a joint
graph, and mutually update their representations through graph neural networks.
We evaluate our model on QA benchmarks in the commonsense (CommonsenseQA,
OpenBookQA) and biomedical (MedQA-USMLE) domains. QA-GNN outperforms existing
LM and LM+KG models, and exhibits capabilities to perform interpretable and
structured reasoning, e.g., correctly handling negation in questions.

该研究提出了一种新模型 QA-GNN，通过关联系统知识图和语言模型，实现对问题与答案之间的共同推理，并取得了在常识和生物医学领域 QA 测试中优于现有模型的表现。