## 2 Materials and Methods  
This section describes the methods and materials adopted for the implementation of the research activities presented in this paper. The methods are focused on the approach adopted for the DT definition, with the following methodologies adopted:  
* User-Centric Design: The project follows a user-centered design (UCD) methodology, prioritizing the needs and expectations of warehouse personnel throughout the development process [23; 24]. This approach involves close collaboration with stakeholders through interviews, workshops, and user acceptance testing to ensure that the final product aligns with their requirements and workflows. With the interview, the warehouse processes, material flows, and data exchange procedures are mapped to identify pain points, inefficiencies, and opportunities for improvement. User stories were created based on the gathered requirements. These stories outlined the specific needs, goals, and expectations of different user groups within the warehouse environment. * Data-Driven Approach: The project analyzes the opportunity for the adoption of a data-driven approach to inform decision-making at every stage. This involves analyzing existing data sources [25; 26] to support further evaluation, different tracking technologies based on quantitative metrics [27], and using real-time data from IoT sensors to monitor and optimize warehouse processes [14]. Data sources and flows of the use case's softwires are analyzed to identify relevant data points for integration into the DT. * Digital Twin Framework: The development of the digital twin is based on the integration of data from Building Information Modeling and Internet of Things technologies, a well-established approach in the literature [28], and includes manufacturing software' data in Enterprise Resource Planning (ERP). The development of optimization algorithms in the DT draws on research on operations and artificial intelligence to find optimal solutions for complex problems in real time. The materials used for the IRIS digital twin design are:Use case: Focchi S.p.A. manufacturing company, which produces prefabricated building envelopes, is based in Poggio Torriana, Rimini (Italy) and is adopted as the use case. Focchi S.p.A. is a family-owned company founded in 1914 and has established itself as a leading player in the construction industry, specializing in delivering high-tech architectural building envelopes for the construction industry based on an engineer-to-order model. Focchi's expertise lies in crafting bespoke facade solutions for unique buildings, blending craftsmanship with cutting-edge technology. Within the construction value chain, Focchi is engaged in the activities of engineering, manufacturing, and installing building envelopes with the purpose of overseeing the stages from design concept validation to final on-site installation (Figure 1). * Company assets: the physical and digital assets are listed as follows:
* Physical assets: three kinds of physical assets are evaluated in the digital twin design:
* Built environment: the Focchi HQ premises is the physical space of the warehouse to be used in the DT. This research focuses on warehouse and external spaces used to store inbound materials and components and outbound prefabricated facades. * Means of transportation: bikes and forklifts used by warehouse operators will be in the DT. * Stillages for components storage: stillages, pallets, and iron steels will be tracked in the DT (Figure 2). * Digital assets: three kinds of digital assets are evaluated in the Digital Twin design for data-driven analysis:
* ERP: this software centralizes and manages various business processes and data, including inventory and orders. * Production Planner: integrated with the ERP and operations, this tool is used by an operator to schedule production processes based on production loads and material inventory analysis. The solution is manually handled.