TLaaS (LEX) — License Registry Smart Contract: ERC‑721/1155 Implementation Guide

1. Purpose of the License Registry

The License Registry smart contract is the on-chain source of truth for all tokenized licenses within TLaaS (LEX). It tracks ownership, rights, validity, and metadata, while integrating with TLAAS (DLA) for validation and DAL for dispute resolution.

2. Choosing a Token Standard

TLaaS supports two primary token standards:

• ERC‑721 – Non-fungible licenses with unique identifiers and distinct rights.
• ERC‑1155 – Semi-fungible licenses that share rights but differ in quantity or holder.

Choose ERC‑721 for unique, individually issued licenses; choose ERC‑1155 for bulk or tiered licensing.

3. Core Contract Functions

Required functions include:

• mintLicense(address to, LicenseMetadata metadata)
• renewLicense(uint256 licenseId)
• transferFrom(address from, address to, uint256 licenseId)
• burn(uint256 licenseId)
• validateLicense(uint256 licenseId)

4. Metadata Integration

The registry should link to metadata using:

• On-Chain Storage for critical fields (issuer, holder, expiry, rights hash).
• Off-Chain Storage (IPFS/Arweave) for detailed metadata and full agreements.
• Validation Hash to ensure off-chain data integrity.

5. Access Control

Use Role-Based Access Control (RBAC) to secure functions:

• Issuer Role – Can mint and update.
• Validator Role – Managed via TLAAS (DLA) to confirm authenticity.
• Admin Role – Governance-controlled.

6. Example ERC‑721 Implementation (Solidity)

pragma solidity ^0.8.0;
import "@openzeppelin/contracts/token/ERC721/ERC721.sol";
import "@openzeppelin/contracts/access/AccessControl.sol";

contract LicenseRegistry is ERC721, AccessControl {
    bytes32 public constant ISSUER_ROLE = keccak256("ISSUER_ROLE");
    bytes32 public constant VALIDATOR_ROLE = keccak256("VALIDATOR_ROLE");

    struct LicenseData {
        uint256 expiry;
        string rightsHash;
    }

    mapping(uint256 => LicenseData) public licenses;

    constructor() ERC721("TLaaS License", "TLLEX") {
        _setupRole(DEFAULT_ADMIN_ROLE, msg.sender);
    }

    function mintLicense(address to, uint256 tokenId, uint256 expiry, string memory rightsHash) public onlyRole(ISSUER_ROLE) {
        _mint(to, tokenId);
        licenses[tokenId] = LicenseData(expiry, rightsHash);
    }

    function renewLicense(uint256 tokenId, uint256 newExpiry) public onlyRole(ISSUER_ROLE) {
        require(_exists(tokenId), "License does not exist");
        licenses[tokenId].expiry = newExpiry;
    }
}

7. Interoperability

• TLAAS (DLA): Verifies on-chain status.
• DAL: Handles disputes over ownership or rights.
• Smart Compliance: Audits transfers and renewals for compliance.

8. Testing & Deployment

• Unit Tests: Cover minting, transferring, renewing, and burning.
• Testnet Deployment: Simulate marketplace transactions.
• Mainnet Deployment: Integrate with TLaaS (LEX) marketplace UI.

Next Article: License Issuance & Renewal Functions — Solidity Code, Validations, and Events