propose xip-fSBT.md

XIPS/xip-fSBT.md

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+---
+xip: 10
+title: Introduce Future SBT
+description: fSBT (Future Soul Bound Token) is a type of token that has a limit on the number of transfers that can be made with it, and can be issued in advance or by a user's account to strengthen its SBT- or NFT-like characteristics, with the owner able to restrict its functions or burn it.
+author: Erick You <[email protected]>
+discussions-to: https://www.xdc.dev/web3isthefuture/wip-xip-proposal-introduce-future-sbt-3g1m
+status: Draft
+type: Standards Track
+category (*only required for Standards Track): XRC
+created: 2023-01-10
+requires (*optional): 10
+---
+
+## Abstract
+fSBT (Future Soul Bound Token) is a type of token that has a limit on the number of transfers that can be made with it, and can be issued in advance or by a user's account to strengthen its SBT- or NFT-like characteristics, with the owner able to restrict its functions or burn it.
+
+## Motivation
+A standard interface allows any tokens on XDC Network to be re-used by other applications: from wallets to decentralized exchanges.
+
+## Specification
+
+### Methods
+
+**NOTES**:
+ - The following specifications use syntax from Solidity `0.4.17` (or above)
+ - Callers MUST handle `false` from `returns (bool success)`.  Callers MUST NOT assume that `false` is never returned!
+
+#### name
+
+returns the name of the token as a string
+
+
+``` js
+function name() public view returns (string)
+```
+
+#### symbol
+
+returns the symbol of the token as a string
+
+
+``` js
+function symbol() public view returns (string)
+```
+
+#### totalSupply
+
+Returns the total token supply.
+
+``` js
+function totalSupply() external view returns (uint256)
+```
+
+#### balanceOf
+
+Returns the account balance of another account with address `owner`.
+
+``` js
+function balanceOf(address owner) external view returns (uint256)
+```
+
+#### transferFrom
+
+Transfers the ownership of a given token ID to another address.
+
+``` js
+function transferFrom(address from, address to, uint256 tokenId) public
+```
+
+#### approve
+
+Approves another address to transfer the given token ID
+
+``` js
+function approve(address to, uint256 tokenId) public
+```
+
+#### limitedTransfer
+
+Transfers _value amount of tokens from address _from to address _to, and MUST fire the Transfer event.
+
+The limitedTransfer method is used for a withdraw workflow, allowing contracts to transfer tokens on your behalf. This can be used for example to allow a contract to transfer tokens on your behalf and/or to charge fees in sub-currencies. The function SHOULD throw unless the _from account has deliberately authorized the sender of the message via some mechanism.
+
+Transfers of 0 values MUST be treated as normal transfers and fire the Transfer event.
+
+``` js
+function limitedTransfer(address _from, address _to, uint256 _value) public returns (bool success)
+```
+
+#### batchRevoke
+
+Revokes the specified tokens.
+
+``` js
+function batchRevoke(uint256[] memory _tokenIds) public returns (bool success)
+```
+
+#### batchAttest
+
+Attests the specified tokens.
+
+``` js
+function batchAttest(uint256[] memory _tokenIds) public returns (bool success)
+```
+
+### Events
+
+#### Transfer
+
+MUST trigger when tokens are transferred, including zero value transfers.
+
+A token contract which creates new tokens SHOULD trigger a Transfer event with the `_from` address set to `0x0` when tokens are created.
+
+``` js
+event Transfer(address indexed _from, address indexed _to, uint256 _value)
+```
+
+#### Approval
+
+MUST trigger on any successful call to `approve(address _spender, uint256 _value)`.
+
+``` js
+event Approval(address indexed _owner, address indexed _spender, uint256 _value)
+```
+
+#### Revoke
+
+MUST trigger when tokens are revoked.
+
+``` js
+event Revoke(uint256 indexed _tokenId)
+```
+
+#### Attest
+
+MUST trigger when tokens are attested.
+
+``` js
+event Attest(uint256 indexed _tokenId)
+```
+
+#### OwnershipTransferred
+
+MUST trigger when token ownership is transferred.
+
+``` js
+event OwnershipTransferred(uint256 indexed _tokenId, address indexed _prevOwner, address indexed _newOwner)
+```
+
+## Rationale
+This document was derived heavily from [BNB Chain's BEP-179](https://github.com/bnb-chain/BEPs/pull/179) and the interface is fully compatible with BNB Chain's fSBT. This makes it easy to reuse code and tools from the Ethereum ecosystem.
+
+## Reference Implementation
+Examples of future SBTs can be used as a reference implementation, which are available at
+
+- [CatzeLabs implementation](https://github.com/catze-labs/futureSBT/)
+- [Binance Evolution Proposal](https://github.com/bnb-chain/BEPs/pull/179)
+
+## Copyright
+Copyright and related rights waived via [CC0](../LICENSE.md).