## 4 System Realization
### Traceability System Architecture Design  
Considering the many suppliers in industrial product manufacturing; the variety of parts and components; the massive heterogeneity of the production management data; the demand for information sharing in industrial product manufacturing; the cost and scalability of handling and the inability to handle highly concurrent large-scale data; and the throughput constraints of blockchain technology, this study tries to adopt the \"alliance chain + private chain\" model based on the technical architecture in Section 2.2 to build a hybrid blockchain for a industrial product quality traceability system, as shown in Figure 3.  
Hybrid blockchain is a blockchain technology architecture that combines the characteristics of an alliance chain [29] and a private chain [30], which is adapted from the alliance chain by replacing the participating nodes with a combination of \"nodes + private chain\". Compared to the traditional alliance chain model, the hybrid blockchain stores the data by transmitting valuable information in the data that needs to be shared with the corresponding alliance chain node of the private chain. The hybrid blockchain architecture retains the advantages of alliance chains, such as permission control and high-performance consensus mechanisms. At the same time, introducing a private chain solves the defects of the traditional alliance chain mode, such as excessive node storage, low throughput, and high cost. Sharing data flexibly between alliance chain nodes and private chains ensures data security and privacy, reduces the pressure of overall data processing and storage, and improves system efficiency and performance. The system architecture of this industrial product quality traceability system consists of an alliance chain and multiple private chains, in which the alliance chain consists of the whole life cycle supervision, the General Administration of Market Supervision, the production and manufacturing of industrial products, industry and commerce, quality inspection, product stockpiling, finance, the Ministry of Industry and Informatization, logistics, environmental protection, and other departments as nodes. According to the \"Supervision and Management Provisions on the Implementation of Quality and Safety Responsibility of Industrial Product Manufacturing Units\" and \"Supervision and Management Provisions on the Implementation of Quality and Safety Responsibility of Industrial Product Sales Units\" issued by the General Administration of Market Supervision and Regulation, and in combination with the market circulation norms for industrial products, we will arrange and deploy the nodes of the alliance chain mentioned above according to their functions and classify them into four subsystems, which are the production and manufacturing subsystem; the sales, circulation, transportation, and logistics subsystem, the product reserve subsystems; and the regulatory subsystems, respectively, to build a private chain of the four subsystems. Based on the data interactions and storage requirements for the quality information on the whole life cycle of industrial products, the hybrid blockchain adopts the Interplanetary file system (IPFS) network. Constructed based on BitTorrent protocol and Kademlia Distributed Hash Table (DHT) technology, it ensures that the peer nodes in the network structure can conveniently relocate objects and manage metadata, and each private chain interacts with alliance chains through a proxy server for data interaction and information sharing. Product design/decision-making, raw material procurement/supply, product manufacturing/production processes and early warnings, product warehousing/stockpiling, sales/packaging, logistics/transportation, use/condition monitoring, maintenance/inspection and repair, decommissioning/recycling and remanufacturing,  
Figure 3: Industrial product quality traceability blockchain platform architecture.