Digital Twins (DT) facilitate monitoring and reasoning processes in cyber-physical systems. They have progressively gained popularity over the past years because of intense research activity and industrial advancements. Cognitive Twins is a novel concept, recently coined to refer to the involvement of Semantic Web technology in DTs. Recent studies address the relevance of ontologies and knowledge graphs in the context of DTs, in terms of knowledge representation, interoperability and automatic reasoning. However, there is no comprehensive analysis of how semantic technologies, and specifically ontologies, are utilized within DTs. This Systematic Literature Review (SLR) is based on the analysis of 82 research articles, that either propose or benefit from ontologies with respect to DT. The paper uses different analysis perspectives, including a structural analysis based on a reference DT architecture, and an application-specific analysis to specifically address the different domains, such as Manufacturing and Infrastructure. The review also identifies open issues and possible research directions on the usage of ontologies and knowledge graphs in DTs.

翻译：数字孪生（DT）促进了信息物理系统中的监控与推理过程。近年来，随着研究活动的密集开展和工业技术的进步，数字孪生日益普及。认知孪生是一个新近提出的概念，特指语义网技术在数字孪生中的应用。近期研究从知识表示、互操作性和自动推理等角度，探讨了本体论与知识图谱在数字孪生中的相关性。然而，目前尚缺乏关于语义技术（尤其是本体论）如何在数字孪生中应用的全面分析。本系统性文献综述（SLR）基于82篇研究论文展开分析，这些论文或提出了数字孪生相关的本体论，或从中受益。本文采用了多种分析视角，包括基于参考数字孪生架构的结构分析，以及针对制造、基础设施等不同领域的应用特定分析。此外，本综述还指出了本体论与知识图谱在数字孪生应用中存在的开放性问题与潜在研究方向。