Metadata standard
The Marmalade v2 metadata standard, serves as a crucial component for constructing a comprehensive and comprehensible profile for each NFT. Now, it may seem a little intimidating at first glance, but when you break it down, it's really a guide to how we describe the unique features of each Non-Fungible Token (NFT) on the Marmalade platform.
This schema provides the structural foundation for key attributes of an NFT, each representing an integral facet of the NFT's identity. However, the schema also allows for the addition of arbitrary properties that serve to enhance the individuality of each token.
JSON standard
A significant characteristic of marmalade involves the URI attribute, a pointer to an off-chain JSON file. This design ensures the delivery of useful information on tokens without straining the constraints imposed by on-chain data storage fees.
The off-chain schema contains properties that describe the metadata of an NFT stored off-chain in a JSON format. The schema includes the following fields:
| Field Name | Data Type | Description |
|---|---|---|
| name | string | Identifies the asset to which this NFT represents |
| description | string | Describes the asset to which this NFT represents |
| *image | string | A URI pointing to a resource with mime type image/* representing the asset to which this NFT represents. Consider making any images at a width between 320 and 1080 pixels and aspect ratio between 1.91:1 and 4:5 inclusive. |
| *properties | object | Arbitrary properties. Values may be strings, numbers, object or arrays. |
| *authors | array of objects | An array of authors who created or contributed to the asset. Each author is an object with a "name" field specifying the author's name. |
| *external_url | string | URL to an external application or website where users can also view the asset |
| *animation_url | string | URL to a multimedia attachment of the asset. The supported file formats are MP4 and MOV for video, MP3, FLAC and WAV for audio, GLB for AR/3D assets, and HTML for HTML pages. You may use the ?ext={file_extension} query to provide information on the file type. |
| *collection | object | an object with a "name" field specifying the name of the collection, and a “family” field specifying the larger category or group to which the collection belongs. |
* optional
JSON Schema
{ "title": "Token Metadata", "description": "Schema for non-fungible token (NFT) metadata.", "type": "object", "required": ["name", "description"], "properties": { "name": { "type": "string", "description": "Identifies the asset to which this NFT represents." }, "description": { "type": "string", "description": "Describes the asset to which this NFT represents." }, "image": { "type": "string", "format": "uri", "description": "A URI pointing to a resource with mime type image/* representing the asset to which this NFT represents. Consider making any images at a width between 320 and 1080 pixels and aspect ratio between 1.91:1 and 4:5 inclusive." }, "properties": { "type": "object", "description": "Arbitrary properties. Values may be strings, numbers, objects or arrays." }, "external_url": { "type": "string", "format": "uri", "description": "URL to an external application or website where users can also view the asset." }, "animation_url": { "type": "string", "format": "uri", "description": "URL to a multimedia attachment of the asset. The supported file formats are MP4 and MOV for video, MP3, FLAC and WAV for audio, GLB for AR/3D assets, and HTML for HTML pages. You may use the ?ext={file_extension} query to provide information on the file type." }, "authors": { "type": "array", "items": { "type": "object", "properties": { "name": { "type": "string", "description": "The author's name." } } }, "description": "An array of authors who created or contributed to the asset." }, "collection": { "type": "object", "properties": { "name": { "type": "string", "description": "The name of the collection." }, "family": { "type": "string", "description": "The larger category or group to which the collection belongs." } }, "description": "An object specifying the name and family of the collection to which this NFT belongs." } }}{ "title": "Token Metadata", "description": "Schema for non-fungible token (NFT) metadata.", "type": "object", "required": ["name", "description"], "properties": { "name": { "type": "string", "description": "Identifies the asset to which this NFT represents." }, "description": { "type": "string", "description": "Describes the asset to which this NFT represents." }, "image": { "type": "string", "format": "uri", "description": "A URI pointing to a resource with mime type image/* representing the asset to which this NFT represents. Consider making any images at a width between 320 and 1080 pixels and aspect ratio between 1.91:1 and 4:5 inclusive." }, "properties": { "type": "object", "description": "Arbitrary properties. Values may be strings, numbers, objects or arrays." }, "external_url": { "type": "string", "format": "uri", "description": "URL to an external application or website where users can also view the asset." }, "animation_url": { "type": "string", "format": "uri", "description": "URL to a multimedia attachment of the asset. The supported file formats are MP4 and MOV for video, MP3, FLAC and WAV for audio, GLB for AR/3D assets, and HTML for HTML pages. You may use the ?ext={file_extension} query to provide information on the file type." }, "authors": { "type": "array", "items": { "type": "object", "properties": { "name": { "type": "string", "description": "The author's name." } } }, "description": "An array of authors who created or contributed to the asset." }, "collection": { "type": "object", "properties": { "name": { "type": "string", "description": "The name of the collection." }, "family": { "type": "string", "description": "The larger category or group to which the collection belongs." } }, "description": "An object specifying the name and family of the collection to which this NFT belongs." } }}JSON Basic example
{ "name": "My NFT", "description": "This is my awesome NFT", "image": "https://example.com/my-nft.jpg"}{ "name": "My NFT", "description": "This is my awesome NFT", "image": "https://example.com/my-nft.jpg"}JSON Additional fields example
{ "name": "My NFT", "description": "This is my non-fungible token.", "image": "https://example.com/image.png", "external_url": "https://example.com", "animation_url": "https://example.com/animation.mp4", "authors": [ { "name": "John Doe" }, { "name": "Jane Smith" } ], "collection": { "name": "My Collection", "family": "Art" }}{ "name": "My NFT", "description": "This is my non-fungible token.", "image": "https://example.com/image.png", "external_url": "https://example.com", "animation_url": "https://example.com/animation.mp4", "authors": [ { "name": "John Doe" }, { "name": "Jane Smith" } ], "collection": { "name": "My Collection", "family": "Art" }}JSON Properties example
{ "name": "Sword of the Thunder God", "description": "A legendary sword imbued with the power of the thunder god.", "image": "https://example.com/sword-of-thunder-god.jpg", "properties": { "damage": 50, "element": "Thunder", "rarity": "Legendary" }, "external_url": "https://example.com/sword-of-thunder-god", "authors": [ { "name": "John Smith" } ], "collection": { "name": "Legendary Weapons", "family": "Fantasy" }}{ "name": "Sword of the Thunder God", "description": "A legendary sword imbued with the power of the thunder god.", "image": "https://example.com/sword-of-thunder-god.jpg", "properties": { "damage": 50, "element": "Thunder", "rarity": "Legendary" }, "external_url": "https://example.com/sword-of-thunder-god", "authors": [ { "name": "John Smith" } ], "collection": { "name": "Legendary Weapons", "family": "Fantasy" }}Pact schema
With marmalade V2, the on-chain metadata schema for non-fungible tokens (NFTs) has been deprecated. This means that the manifest schema, which was previously used to store the metadata for NFTs on-chain, is no longer being used. Instead, a new schema has been introduced, which is off-chain and conforms to the widely accepted standard for NFT metadata.
(defschema token-schema manifest:object{manifest} ... ) (defschema token-schema manifest:object{manifest} ... )Has been replaced with:
(defschema token-schema uri:string ... ) (defschema token-schema uri:string ... )Token schema now has the following structure:
(defschema token-schema id:string uri:string precision:integer supply:decimal policies:[module{kip.token-policy-v2}] ) (defschema token-schema id:string uri:string precision:integer supply:decimal policies:[module{kip.token-policy-v2}] )- uri: A string representing the URI that points to an external JSON-Schema for the NFT.
Generating t:{hash}
The previous schema used by Marmalade V1 was called 'manifest', and it consisted of a URI, a hash value, and an array of data objects. To create a new manifest, the 'create-manifest' function was used, which took a URI object and an array of data objects as input. The 'create-datum' function was used to create a data object, which consisted of a URI object and a datum object. The 'verify-manifest' function was used to verify that a given manifest was valid, and the 'enforce-verify-manifest' function was used to enforce the validity of a manifest.
(defschema token-details uri:string precision:integer policy:module{kip.token-policy-v2} ) (defschema token-details uri:string precision:integer policy:module{kip.token-policy-v2} )Since onchain manifest is deprecated, token-details schema is hashed.
The reason for hashing the token-details is to capture all the data on the ledger for cross-chain data. Previously, the manifest was hashed to create a unique identifier for each NFT, but now the token-details schema is hashed to create a unique identifier for each NFT.
Rationale
Why the Manifest was Replaced by URI
We decided to replace the manifest schema with a URI-based schema. The new schema for NFT metadata is a simple JSON schema that describes the properties of the metadata. This schema enables compatibility with various marketplaces and wallets, making Marmalade tokens more interoperable. By utilising a URI-based schema, Marmalade tokens can improve scalability, and provide greater flexibility for developers and most of all simplicity of usage in general.
The decision to move NFT metadata off-chain and use a widely accepted standard for the metadata schema is a positive step for Marmalade tokens.
The Marmalade v2 metadata standard for Non-Fungible Tokens (NFTs) adheres closely to the widely recognised ERC1155 "metadata standard". By aligning with this well-established standard, Marmalade enables seamless portability and interoperability of NFTs between the Ethereum network and the Kadena blockchain.
Both standards share similar fundamental attributes for describing NFTs. Marmalade v2 also supports additional optional fields, including "properties," which allow for the inclusion of arbitrary properties to enhance the uniqueness and individuality of each token. Similarly, the ERC1155 "metadata" standard" includes the "properties" field, ensuring compatibility between the two standards in terms of extensibility.
Another addittion to Marmalade v2 is the inclusion of the "authors" field, which enables the attribution of the individuals who created or contributed to the asset. This promotes transparency and recognition of the artistic and creative contributions associated with each NFT.
Marmalade v2 recognises the importance of categorisation and collection organization. The "collection" field in Marmalade v2, allows for specifying the name and family of the collection to which the NFT belongs. This categorisation provides context and grouping, facilitating efficient management and discovery of NFTs within a broader ecosystem.
In summary, Marmalade's adoption of the ERC1155 "metadata standard" showcases a dedication to following established industry norms, ensuring consistency, compatibility, and ease of migration for NFTs. This commitment enables a broader range of users to participate in the vibrant world of digital collectibles while fostering interoperability between different blockchain ecosystems.