  Natural Language Inference (NLI) is fundamental to many Natural Language
Processing (NLP) applications including semantic search and question answering.
The NLI problem has gained significant attention thanks to the release of large
scale, challenging datasets. Present approaches to the problem largely focus on
learning-based methods that use only textual information in order to classify
whether a given premise entails, contradicts, or is neutral with respect to a
given hypothesis. Surprisingly, the use of methods based on structured
knowledge -- a central topic in artificial intelligence -- has not received
much attention vis-a-vis the NLI problem. While there are many open knowledge
bases that contain various types of reasoning information, their use for NLI
has not been well explored. To address this, we present a combination of
techniques that harness knowledge graphs to improve performance on the NLI
problem in the science questions domain. We present the results of applying our
techniques on text, graph, and text-to-graph based models, and discuss
implications for the use of external knowledge in solving the NLI problem. Our
model achieves the new state-of-the-art performance on the NLI problem over the
SciTail science questions dataset.
