ERC-1948: Non-fungible Data Token
Simple Summary
Some NFT use-cases require to have dynamic data associated with a non-fungible token that can change during its lifetime. Examples for dynamic data:
- cryptokitties that can change color
- intellectual property tokens that encode rights holders
- tokens that store data to transport them across chains
The existing metadata standard does not suffice as data can only be set at minting time and not modified later.
Abstract
Non-fungible tokens (NFTs) are extended with the ability to store dynamic data. A 32 bytes data field is added and a read function allows to access it. The write function allows to update it, if the caller is the owner of the token. An event is emitted every time the data updates and the previous and new value is emitted in it.
Motivation
The proposal is made to standardize on tokens with dynamic data. Interactions with bridges for side-chains like xDAI or Plasma chains will profit from the ability to use such tokens. Protocols that build on data tokens like distributed breeding will be enabled.
Specification
An extension of ERC-721 interface with the following functions and events is suggested:
Rationale
The suggested data field in the NFT is used either for storing data directly, like a counter or address. If more data is required the implementer should fall back to authenticated data structures, like merkle- or patricia-trees.
The proposal for this ERC stems from the distributed breeding proposal to allow better integration of NFTs across side-chains. ost.com, Skale, POA, and LeapDAO have been part of the discussion.
Backwards Compatibility
š¤·āāļø No related proposals are known to the author, hence no backwards compatibility to consider.
Test Cases
Simple happy test:
Implementation
An example implementation of the interface in solidity would look like this:
Copyright
Copyright and related rights waived via CC0.