Abstract

A knowledge graph is a multidirectional labelled graph used for the graphical representation of knowledge where each node represents an entity, and the edge connecting the two nodes represents a relationship. There has been a rise in the popularity of using knowledge graph in information retrieval, recommender system, dialogue system, and question-answering system. The question-answering system can be either over structured data or unstructured data. This article studies the existing techniques for questionanswering systems over knowledge graph. We collect 43 articles on the question-answering system over a knowledge graph. We give a brief introduction to knowledge graph and question-answering system. Further, we discuss challenges, datasets and evaluation metrics used to evaluate techniques. Finally, we conclude the article by discussing some open research aspects, highlighting factors of the low-resource language for question-answering systems over knowledge graph and remarks on existing systems.