A guide to Non-Fungible Tokens (NFTs), 2023 - Flipbook - Page 7
The metadata is referenced by a cryptographically uniform resource identifier
(URI) within the smart contract code of an NFT. For example, the Ethereum
token standard smart contract for NFTs, ERC-721, contains a specific string
of code (the URI) which references the metadata associated with the NFT and
the associated asset. ERC-721 smart contracts link to metadata in a JavaScript
Object Notation (JSON) format. The URI will specify a JSON file. What exactly
the JSON file, or other metadata file, will contain depends on the form of the
underlying asset itself and the choices made when minting the NFT.
The underlying asset could take the form of a:
•
Physical asset: for example, a painting or pair of trainers. In this instance,
the NFT would serve as a certificate of ownership and authenticity for that
physical asset. In recent times, a number of artworks have been sold with
corresponding NFTs, but the technology has also been used in other spheres,
such as gaming and fashion, where NFTs have been linked to merchandise
or clothing items. Often the metadata will contain or link to a copy of a visual
representation of the physical asset, but the terms of the smart contract
may also attempt to refer to or transfer ownership of the physical asset.
•
Digital native metadata file of the work: a metadata file containing a
digital asset, for example a digitally created artwork.
•
Digital copy of a physical work metadata file: a metadata file containing a
copy of a physical asset, for example a scan of a photograph.
•
Linked digital copy: a metadata file containing a link to a site hosting a
digital copy of a digital asset, for example a digitally created artwork.
•
Linked digital copy of physical work: a metadata file containing a link to
a site hosting a digital copy of a visual representation of a physical asset,
for example, a scan of a photograph.
•
Blockchain embedded file: certain very small files can be incorporated
into the blockchain code themselves (as opposed to being contained in
the metadata), but this is rare as it increases “gas” fees
6
