Categorization of Digital Twins: A Literature Review of IoT and Industry

In recent years, the digital twin concept has gained traction in both academia and industry. But what is a digital twin? It is quite common to see many kinds of publications from scientific research to news articles on digital twins mentioning that there is no exact definition for the term. In this paper, we will go through the digital database of IEEE Xplore in an attempt to find out how the publications on digital twins use the term, and how the twins could be categorized and defined more clearly. Our focus is on literature that studies the digital twins within the context of Internet-of-Things (IoT) and industry. Our studies will show that there is indeed a need for a more standardized definition for the term, and that digital twin is often used as a blanket term to cover many systems, prototypes and implementations that may or may not be actual digital twins.