# When Operation Technology Meets Information Technology: Challenges and Opportunities
## 3 State of the Art in I4.0  
Nowadays, shop floors constitute a very complex environment, mixing a plethora of devices, spanning from natively IoT-enabled [23] ones to legacy systems. On the one hand, OT systems are built in order to facilitate the automation of production processes for in-plant and near-real-time data gathering, control, and monitoring [24]. In addition, the OT layer comprises a wide range of protocols that are incompatible with one another and lead to fragmentation, making it difficult to provide a coherent and consolidated view of the assets and processes [25]. On the other hand, IT networks are primarily used to collect, manipulate, and analyze information to generate insights.  
Moreover, the current trend in factory automation verges towards connecting the factory floor to all other enterprise processes. The adoption of cloud platforms [26] ensures the needed scalability of storage, computation, and cross-domain communication capabilities but also poses a number of novel cyber-security threats to the manufacturing environment [27].  
To handle this heterogeneity, it is very useful to focus on a possible architecture that embraces both worlds: state-of-the-art IT and OT tools and technology. For this reason, the Reference Architecture Model for Industry 4.0 (RAMI 4.0) [28] defines a reference architectural model to align standards in the context of I4.0. It consists of a three-dimensional coordinate system that describes all the crucial aspects needed for the implementation of Industry 4.0. In RAMI 4.0, a central focus is given to the management of physical assets: the Asset Administration Shell (AAS) constitutes a digital representation of a physical asset and is deemed essential to the implementation of a digital twin for I4.0. It performs the roles of asset, communication, information, and function layers in RAMI 4.0 [7]. An implementation of the AAS, which is standard compliant, is Eclipse BaSyx, which acts as a middleware and offers a new service-oriented architecture for I4.0 that can fill the gap present in today's shop floors. The purpose of Basyx is primarily to be open and permit highly interconnected automation systems to share data across several layers of the automation pyramid.  
In addition, RAMI 4.0 recommends only the International Electrotechnical Commission (IEC) standard 62541 OPC Unified Architecture (OPC UA) for implementing the communication layer [29] in order to enable information exchange between the shop floor and the enterprise systems. OPC UA is a platform-independent industrial communication protocol that addresses the need for the Industrial Internet of Things (IIoT) and the Industry 4.0 paradigm for standardized data connectivity and interoperability for both horizontal and vertical data communications. In particular, horizontal integration refers to controller-to-controller or machine-to-machine (M2M) communication, whereas vertical integration refers to communications from sensors/actuators and controllers in the field to IT systems or the cloud and vice versa [30].  
Nevertheless, to enable smooth and efficient operation and fast responses to warnings and failures, the communication should be performed with very low latency [31]. In this context, ultra-low latency refers to the ability to process and transmit data with minimal delay, typically on the order of microseconds or less. This is essential for enabling real-time decision-making and control in Industry 4.0 applications, such as predictive maintenance, automated production, and remote monitoring and control. For instance, a hybrid ultra-low latency system might incorporate high-speed networks, such as TSN (Time-Sensitive Networks), to ensure fast data transmission, as well as specialized hardware, such as field-programmable gate arrays (FPGAs) or application-specific integrated circuits (ASICs), to enable real-time data processing. In addition, the system could incorporate advanced algorithms and machine learning techniques to improve the efficiency and accuracy of data processing and decision-making.