## 3 Design of NexoNet System
### System Model  
The NexoNet, as a BOSM, relies on blockchain technology and engages users in content creation and purchasing activities within the platform. NexoNet comprises four main roles: users, blockchain system, maintainers, and decentralized application (DApp). The system model is shown in Figure 1, while facilitating social media functionalities, it also embodies the characteristics of decentralization, traceability, and security efficiency. In the proposed NexoNet, maintainers are responsible for the technical maintenance of the blockchain system, such as verifying transactions and generating blocks. However, their authority is strictly limited, and they are subject to the PoAP consensus mechanism and user voting. Users do not directly partake in the blockchain consensus mechanism, such as transaction verification and block generation, to prevent imposing additional burdens on them, like the need for more advanced hardware or increased complexity in usage. Therefore, in the NexoNet, tasks related to the operation and maintenance of the blockchain, such as running the consensus mechanism, are delegated to maintainers in the system. Users participate in the consensus by voting for maintainers, thereby engaging in the system's governance and benefiting from incentive mechanism. The functionalities of each role are described as follows:  
Users: As the protagonists of the NexoNet, users are the source of all value within it. Users assume dual roles: as system users, they can be content producers, publishing content that they create; as content consumers, they can purchase and evaluate content. As owners of the system, users participate in its operation and maintenance through voting, thereby influencing its development direction. Blockchain system: The blockchain serves as the technological foundation of the NexoNet, responsible for storing users' transaction and state information in a decentralized manner and using Merkle trees to store these data within blocks. Cryptography and blockchain structure ensure the traceability and immutability of system information. With each new block's generation, the system's intrinsic multiple incentive mechanism rewards users and maintainers who contribute to the system. Maintainers: Maintainers equipped with necessary hardware and maintaining an online presence, are responsible for the daily maintenance of the blockchain system and supporting various system functions. Their duties include transaction verification and forwarding, block generation, decentralized storage, maintenance of content and account information, and responding to users' transaction requests. DApp: DApp is the interface for user-system interaction, facilitate account management and system interaction for users, such as scanning, generating, and purchasing content. DApp transmits user data to blockchain maintainers and return information from the blockchain to users for visualization. The workflow of the NexoNet is described as follows:  
1. Content publication and interaction: Users can publish content and purchase, reward, and rate content in the NexoNet through transactions sent via DApp. DApp forwards these transactions to maintainers, who serialize them and broadcast them across the network to all maintainers. All maintainers store the received valid transactions in a transaction pool. 2. Voting and consensus: At the start of each voting cycle, users vote for the maintainers they trust. Upon receiving votes, maintainers initiate the PoAP consensus mechanism, electing a committee and a block proposer through a cryptographic sortition algorithm. The proposer then proposes a new block to all committee members for a four-phase consensus process. 3. Block verification and broadcasting: After the committee generates a block, it is broadcast to all maintainers for verification. If the block is verified by a majority of maintainers, it is added to the blockchain.