## 3 System Model Definition
### System Roles' Definition  
Before explaining the system architecture of dNAS based on the gathered system requirements, the constituent system roles and their corresponding use cases are clarified. In dNAS, the decentralized architecture and anti-counterfeiting mechanism are built around a concept of enterprise consortium consisting of winemakers and the supply chain participant nodes along the supply chain. Similar to those defined in the legacy NAS, there are four main system roles in the proposed system model of dNAS, depicted as follows.  
_The Winemaker Role_: The winemaker is the manufacturer of wine products. The provided functions of winemakers include (1) creating new wine records with a set of wine pedigree data, supply chain data and transaction data, (2) proposing that their supply chain participants are added to or removed from the consortium, as well as their designated blockchain nodes to the blockchain network, (3) setting the quantity of wine products available to be sold, and (4) retrieving information regarding its supply chain participants so that the latest status of sales can be retrieved. The winemaker role can also inquire about any wine product their participants have been marketing to wine consumers, and verify whether specific wine products have been recalled or exchanged, or confirm if the current status of these wine products has been verified with public addresses provided by related wine consumers.  
_The Supply Chain Participant Role_: The supply chain participants could have the role of wholesaler, retailer or reseller, and literally any supply chain node after winemakers and prior to wine consumers, along the supply chain. Participants can use functions of dNAS to encrypt wine record components using private keys, and wine consumers can, therefore, utilize the concept of asymmetric cryptography, which is applied to the system functions of its blockchain service, hosted by the consortium administrator. The participants' public addresses are utilized to verify if the participant is who they claim to be. After performingeach transfer operation, the participant will update the data fields of the transaction data and supply chain data, and the updated content hash is, therefore, pushed on-chain, and available for the registered nodes of winemaker role and supply chain participant role, to obtain the required data.  
_The Wine Consumer Role_: The wine consumers are the end purchasers of wine products. The wine consumer can verify whether a specific supply chain participant is in a business relationship with another winemaker, and also verify whether the supply chain participant has an inventory of specific wine products. Wine consumers can prove that their identities are consistent with their public addresses, and obtain the individual transaction records and wine statuses of wine records via linking the corresponding blockchain nodes to a specific block explorer to review targeted blocks and transactions. As long as a wine product is transferred by a registered node of the wine-consumer role, the authenticity and end-to-end traceability will be assured and legitimate, even beyond any retailer point post-supply-chain.  
_The Consortium Administrator Role_: A _consortium_ consists of winemakers and supply-chain participants. The consortium administrator is elected through a democratic process involving every consortium member, who is assigned their own blockchain service instance with a designated blockchain node running on the blockchain network, which is managed by the consortium. The proposed dNAS would assume that there is only one administrator node elected for the _enterprise consortium_ in this research, for ease of operation and presentation. The possible approach of having on-chain governance aspects to decentralize the enterprise consortium, or enhance the degree of dNAS decentralization as a whole, should be covered in future work on implementing dNAS.