## 2 Background and Related Work
### FIWARE as a Reference Architecture for a Smart Industry  
FIWARE is an open, generic, and extensible platform primarily focused on supporting the development of smart environment applications. FIWARE facilitates access to a rich set of universal and easy-to-use Web Services, which enable the storage and management of data from different sources and devices. Currently, it is considered a highly used DT RA in multiple sectors and domains [41; 42]. With this extensive usage of RA to facilitate interoperability between systems, reduce integration costs and risks, and facilitate the adoption of standards and best pracises, FIWARE has become a common middleware implementation due to its open source capabilities and wide support from research activities [43]. This extensive research support facilitated FIWARE's incorporation of components, namely Generic Enablers, which open up the development of new smart applications, solving the issues of heterogeneous environments, overcoming different protocol approaches, or improving the capacities of the stored information. The objective of this work is to provide users of FIWARE generic enablers with the possibility of closing the gap between Linked Data vocabularies and functional APIs of IoT systems in the manufacturing industry domain. Currently, FIWARE, contrary to other platforms, in addition to offering a set of tools and services to facilitate the development of smart solutions, also provides a set of standards for context data management through its context broker, namely the Orion Context Broker [44]. In a FIWARE architectural deployment, all communication between applications and IoT devices is performed by the Context Broker, which means that this GE performs the communication between the producers of information and their consumers. The Orion LD Context Broker offers advanced capabilities for data ingestion, storage, query processing, and real-time event handling [45]. In our research, we leveraged the Orion LD Context Broker to efficiently store and manage the FIWARE Alert entities generated by the FIWARE Interoperability Layer (FIL) component. This allowed us to seamlessly integrate and process contextual data obtained from OPC UA sources. However, data format generates an issue for real industrial environments. Data in FIWARE is represented in the FIWARE NGSI format. There are two leading versions of this format: NGSI v2 and NGSI-LD. However, the main implementation of Context Broker that supports this NGSI-LD (i.e., Orion-LD Context Broker, developed as a part of the FIWARE platform) is in the alpha development stage. It raises concerns for its smooth adoption in real factories. The Orion LD Context Broker's support for standard APIs and its seamless integration with other FIWARE components further enhanced the interoperability and data management capabilities of our solution. By leveraging the Orion LD Context Broker, we were able to harness the power of FIWARE's data-driven approach and unlock new possibilities for advanced IoT applications. The functionality offered by Context Broker can be exploited due to operations compressed within exposed NGSI-LD APIs. As a notable open-source platform, FIWARE facilitates the delineation of interfaces utilising the OpenAPI Specification (OAS). This not only aids in the creation of web applications that implement the REST interface but also enhances communication between consumers and remote services, eliminating the necessity to access source code, refer to documentation, or conduct network traffic scrutiny. Some projects such as Connected Factories have tested some interoperability issues using current FIWARE Connector implementations, specifically lack of connectivity of shop floor sites which were deploying the components in local instances not connected to the internet. This requires an additional implementation to overcome the impossibility of deploying a data space based on standards [46].