## 3 Development of the ICSPB-IoT Conceptual Framework
### Establishment of the ICSPB-IoT Framework  
Based on the above demand analysis, the ICSPB-IoT should comprise four systems, namely, the Project-level Information Integration Center (PIIC), IoT-BIM-based Database (IBD), Government Monitoring and Traceability System (GMTS), and Digital Information System for Engineering Products (DISEP). The PIIC directly collects, classifies, and processes information about the status and attributes of construction resource elements at various stages across project design, manufacturing, transportation, and hoisting, to achieve full transparency of the environment, data and workers' behavior during the construction process. This is an open system with standard data interfaces, and the \"plug and play\" form makes it applicable to every prefabricated building project. An IoT standard system supporting the intelligent construction of prefabricated buildings must be established firstly, including the unified operation standard, the standard of IoT information collection and transmission, the interaction standard among the participants, etc. Finally, these standards form the ICSPB-IoT standard system to guide participants to adopt the IoT. The IBD, which is often managed by a third-party supervisor, is often used to regulate the construction process and facilitate information interactions between contractors. It includes two aspects of data, namely industry-standard data related to safety, quality, technology, cost, duration and other design parameters, and real-time data providing decision support for users. Then, the comparative analysis results of the above two data sources are transmitted to the GMTS and the contractors' OA (Office Automation) systems. If there are irregular operations, the regulatory authorities can require prompt corrections. Besides, combined with the two aspects of data, contractors can develop their own subsystems to support their business, such as the material supply management subsystem, project quality traceability subsystem, engineering safety early warning subsystem, component production planning scheduling subsystem, etc. (see Table 3 for detail). The GMTS established by the government supervision department is the supervision platform of the whole prefabricated buildings industry, which aims to control the quality and safety of the whole process of prefabricated building projects. The system establishes an industry-unified quality and safety database which integrates all aspects of prefabricated building data. The GMTS obtains data on each contractor's subsystems in real-time by interacting with the IBD of the contractors. Then the data are uploaded to the quality and safety database for a comparative analysis. Finally, unqualified work information will be identified and then immediately fed back to the responsible party to find out the cause and corresponding corrections will be required. The DISEP is a system for the construction of digital engineering products of prefabricated buildings by supervisors. The DISEP obtains first-hand information directly from the PIIC (including materials used, construction process, etc.). Building-related information that is not directly available from the PIIC (e.g., the stress resistance which can only be obtained through experiments conducted by manufacturers) can be obtained through connecting with various contractors through the IBD to ensure that the digital engineering products are true mirror images of the physical products. Then, the owners can query the comprehensive information of prefabricated buildings based on digital engineering products. They only need to click on the product component to trace all attributes from the factory to the final building, such as the compression resistance, bending resistance, and node connection process of the component.