# Digital Twin and Internet of Things--Current Standards Landscape
###### Abstract
As industry 4.0 is about optimization on a large scale, interoperability not only within a factory or organization but along the whole value chain is essential and should be addressed globally [20; 21]. Achieving interoperability on a global level requires formal standardization. Multiple SDOs are currently working on standardization of IoT or DT, e.g., the European Telecommunications Standards Institute (ETSI), the International Electrotechnical Commission (IEC), the Internet Engineering Task Force (IETF), the Industrial Internet Consortium (IIC), the International Organization for Standardization (ISO), the Open Geospatial Consortium, the Plattform Industrie 4.0, the World Wide Web Consortium (W3C), and many more. Many of the standards related to DT or IoT address issues that are unique to the domain, i.e., not part of the overlap between IoT and DT, for example, network protocols for wireless connectivity, which belongs to IoT but is not considered a relevant  
Figure 1: Functional overlap between internet of things and digital twins that is subject to standardization in both domains. subject for standardization in the DT domain. Furthermore, different SDOs have different backgrounds and focuses, e.g., ETSI is rooted in the telecommunication domain, OGC focuses on geospatial information management, and the IIC is focused on accelerating the development and adoption of IoT technology in the industry. Several standards that focus on the three basic aspects common to both IoT and DT, resource description, resource discovery, and resource access, are either already existing or currently being developed by different SDOs in parallel. Having multiple competing standards solving the same problem in different ways without aligning with each other massively hinders interoperability. As interoperability is the key requirement of industry 4.0 [21; 22], this is an actual threat for the further development and success of industry 4.0. Previous work focuses on either the IoT or the DT domain or addresses the IoT only as a source of data for DTs, ignoring the fact that the domains actually overlap in functionality. A recent survey from [PERSON] et al. acknowledges the fact that interoperability plays an important role in industry 4.0 on IoT on the DT level and that 'interoperability and standardization will occur as part of the evolution' [23]. Although the relationship and alignment between existing and upcoming IoT and DT standards have been discussed in multiple SDO groups, to the best of the author's knowledge, there has not been any published formalized and structured analysis and comparison. The objective of this paper is to narrow this gap and stimulate the evolution of standards by identifying how well current standards from both the IoT and the DT domain are aligned regarding resource description, discovery and access. This not only provides an overview of the current state of the art on DT interoperability, but can also nourish further consolidation of standards to improve interoperability in industry 4.0. Market research report predicts that until 2027, using DTs will become standard for IoT applications and IoT platforms will support the creation of DTs. At the same time, the total IoT market is predicted to rise from $465 million in 2019 to $1.5 trillion in 2030 whereby 40% thereof depend on successfully addressing interoperability [24; 25; 26]. As 'Industry 4.0 is only possible with the digital twin' [27], identifying and resolving ambiguities in and closing the gap between standards and thereby fostering interoperability is of relevance for the success of industry 4.0. The reminder of the paper is organized as follows. The classification scheme for IoT and DT standards is presented in Section 2. In Section 3, multiple standards from the domains IoT and DT are presented and analyzed based on the previously introduce classification scheme. This is followed by a summary including a comparison matrix discussing the findings and conclusions in Sections 4 and 5, respectively.