  Can language models (LM) ground question-answering (QA) tasks in the
knowledge base via inherent relational reasoning ability? While previous models
that use only LMs have seen some success on many QA tasks, more recent methods
include knowledge graphs (KG) to complement LMs with their more logic-driven
implicit knowledge. However, effectively extracting information from structured
data, like KGs, empowers LMs to remain an open question, and current models
rely on graph techniques to extract knowledge. In this paper, we propose to
solely leverage the LMs to combine the language and knowledge for knowledge
based question-answering with flexibility, breadth of coverage and structured
reasoning. Specifically, we devise a knowledge construction method that
retrieves the relevant context with a dynamic hop, which expresses more
comprehensivenes than traditional GNN-based techniques. And we devise a deep
fusion mechanism to further bridge the information exchanging bottleneck
between the language and the knowledge. Extensive experiments show that our
model consistently demonstrates its state-of-the-art performance over
CommensenseQA benchmark, showcasing the possibility to leverage LMs solely to
robustly ground QA into the knowledge base.
