What is a Knowledge Graph?

Tracking #: 1954-3167

This paper is currently under review
Authors: 
James P McCusker
John S. Erickson
Katherine Chastain
Sabbir Rashid
Rukmal Weerawarana
Deborah L McGuinness

Responsible editor: 
Guest Editors Knowledge Graphs 2018

Submission type: 
Survey Article
Abstract: 
Knowledge graphs have enjoyed a resurgence in research interests after the development of several commercial projects, such as Google's knowledge graph. However, the use of the term has evolved and now may refer to a wide range of graphs, that may not include clear and unambiguous definitions or references. To better provide clarity to knowledge graph research, we survey the literature for current efforts that may inform a knowledge graph definition, and then use that review along with our work to synthesize a definition that is relevant and informative to current knowledge graph research, while constraining the research space that may be considered a knowledge graph. We define a knowledge graph as "A graph, composed of a set of assertions (edges labeled with relations) that are expressed between entities (vertices), where the meaning of the graph is encoded in its structure, the relations and entities are unambiguously identified, a limited set of relations are used to label the edges, and the graph encodes the provenance, especially justification and attribution, of the assertions." We evaluate a wide variety of knowledge resources, graphs, and ontologies to determine if they qualify under our definition, and find that while expressing knowledge as a graph structure and unambiguous denotation of entities and relations in the graph are common, it is less common to trace provenance of encoded knowledge, and less common to constrain the relations used when expressing that knowledge. We created our Knowledge Graph Catalog to support this effort, and make it available to the public to search and contribute new knowledge graphs.
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Under Review