ERC-7507: Multi-User NFT Extension

Abstract

This standard is an extension of ERC-721. It proposes a new role user in addition to owner for a token. A token can have multiple users under separate expiration time. It allows the subscription model where an NFT can be subscribed non-exclusively by different users.

Motivation

Some NFTs represent IP assets, and IP assets have the need to be licensed for access without transferring ownership. The subscription model is a very common practice for IP licensing where multiple users can subscribe to an NFT to obtain access. Each subscription is usually time limited and will thus be recorded with an expiration time.

Existing ERC-4907 introduces a similar feature, but does not allow for more than one user. It is more suitable in the rental scenario where a user gains an exclusive right of use to an NFT before the next user. This rental model is common for NFTs representing physical assets like in games, but not very useful for shareable IP assets.

Specification

Solidity interface available at IERC7507.sol:

Rationale

This standard complements ERC-4907 to support multi-user feature. Therefore the proposed interface tries to keep consistent using the same naming for functions and parameters.

However, we didn't include the corresponding usersOf(uint256 tokenId) function as that would imply the implemention has to support enumerability over multiple users. It is not always necessary, for example, in the case of open subscription. So we decide not to add it to the interface and leave the choice up to the implementers.

Backwards Compatibility

No backwards compatibility issues found.

Test Cases

Test cases available available at: ERC7507.test.ts:

Reference Implementation

Reference implementation available at: ERC7507.sol:

Security Considerations

No security considerations found.

Copyright

Copyright and related rights waived via CC0.