Heuristics for Interpretable Knowledge Graph Contextualization

In this paper, we introduce the problem of knowledge graph contextualization - that is, given a specific context, the problem of extracting the most relevant sub-graph of a given knowledge graph. The context in the case of this paper is defined to be the textual entailment problem, and more specifically an instance of that problem where the entailment relationship between two sentences P and H has to be predicted automatically. This prediction takes the form of a classification task, and we seek to provide that task with the most relevant external knowledge while eliminating as much noise as possible. We base our methodology on finding the shortest paths in the cost-customized external knowledge graph that connect P and H, and build a series of methods - starting with manually curated search heuristics and culminating in automatically extracted heuristics - to find such paths and build the most relevant sub-graph. We evaluate our approaches by measuring the accuracy of the classification on the textual entailment problem, and show that modulating the external knowledge that is used has an impact on performance. 1 Introduction Knowledge Graphs (KGs) contain a very large amount of knowledge about the world and phenomena within it. Such knowledge can be very useful in natural language processing (NLP) tasks such as question answering, textual entailment etc. - tasks that can benefit from a large amount of specialized, domain-specific knowledge. However, recent approaches that have tried to use KGs as sources of external knowledge for the textual entailment problem (Wang et al. 2019) have found that bringing in external knowledge from KGs comes with a significant downside - namely noise that is brought in from the external knowledge. This noise mainly occurs due to the fact that KGs are very large graphs that often contain wrong, repeated, and incomplete information. Retrieving a sub-graph of a given KG that is relevant to a given problem instance is a nontrivial task, and continues to be a topic of much research study.