# NFT-Based Framework for Digital Twin Management in Aviation Component Lifecycle Tracking
## 4 Discussion
### The Relationship Between Updates and the NFT Structure  
The relationship between updates and the NFT structure in the context of aviation-component lifecycle management is a sophisticated interplay among blockchain technology, smart contracts, and decentralized storage (Figure 14).  
The process begins with \"Update sources\" providing new data about the aviation component. These sources could include IoT sensors, maintenance logs, flight data, or manual inputs from technicians. These new data trigger the update process.  
The new data are fed into a smart contract, which is executed on the blockchain. This smart contract is crucial, as it contains the logic to process updates, ensuring that only valid and authorized changes are made to the component's digital representation.  
After processing the update, the smart contract determines the \"Update type\". This classification is a critical step in maintaining the integrity and efficiency of the NFT structure. Figure 14 shows two primary types of updates:  
* Minor updates are frequent, small changes that do not significantly alter the component's status. Examples might include routine sensor readings or minor maintenance checks.
* Major updates are substantial changes that materially affect the component's status or history. Examples could include major repairs, certification renewals, or significant performance alterations.  
For major updates, the process involves updating the NFT metadata. This is a crucial step in the NFT structure, as it allows for significant changes to be recorded directly on the blockchain. The NFT metadata contains essential information about the component, such as its status, ownership history, and critical events in its lifecycle.  
Minor updates are handled differently. Instead of altering the NFT metadata, these updates are recorded in the InterPlanetary file system (IPFS) or other decentralized storage systems. IPFS is a distributed and decentralized file storage and sharing system. It is designed to create a more efficient and resilient method of storing and accessing files, websites, applications, and data [67]. This approach allows for efficient handling of frequent, smaller updates without constantly modifying the blockchain-based NFT.  
The NFT metadata contain a pointer to the latest version of the component data stored in the IPFS. When a major update occurs, this pointer is updated to reflect the new state of the component. For minor updates, a new hash is generated in the IPFS, representing the updated state of the component data.  
The IPFS/decentralized storage plays a crucial role in this structure. It stores the detailed component data, which includes all the historical information and current state of the aviation component. This approach allows for storing large amounts of data off-chain while maintaining a secure, immutable reference on the blockchain via the NFT.  
The blockchain records all major updates and the latest pointers to the IPFS data. This creates an immutable, tamper-proof record of significant events in the component's lifecycle.  
This dual structure of blockchain-based NFT and IPFS storage ensures both the integrity of critical data (through blockchain immutability) and the accessibility and updateability of detailed component information (through IPFS).