string = text .size (0..64)

policy_id = string / bytes ; hex string for CIP-25 version 1, bytes version 2
asset_name = string / bytes ; utf-8 for CIP-25 version 1, bytes for version 2

artist_details =
  {
    name : string,                                                             ; artist or band name
    ? image : string / [* string],      ; optional image of the artist
  }

files_details = 
  {
    name : string,
    mediaType : string,
    src : string / [* string],

    ; For Single, these values are defined at the top level. For Multiple, define them for each track.
    ? artists : [* artist_details],
    ? album_title : string,
    ? track_number: uint,
    ? song_title: string / [* string],
    ? song_duration: string .regexp "^P(?!$)(T(?=\d)(\d+H)?(\d+M)?(\d+S)?)$",    ; iso8601 duration
    ? genres: [1*3 string],
    ? copyright: string,

    ; For Single, these values are defined at the top level. For Multiple, optionally define them for each track
    ? contributing_artists : [* artist_details],
    ? series: string,
    ? collection: string,
    ? set: string,
    ? mood: string,
    ? lyrics: string,
    ? lyricists: [* string],
    ? special_thanks: [* string],
    ? visual_artist: string,
    ? distributor: string,
    ? release_date: string,
    ? publication_date: string,
    ? catalog_number: uint,
    ? bitrate: string,
    ? mix_engineer: string,
    ? mastering_engineer: string,
    ? producer: string,
    ? co_producer: string,
    ? featured_artist: artist_details,
    ? recording_engineer: string,
    ? release_version: uint,
    ? parental_advisory: string,
    ? explicit: bool,
    ? isrc: string,
    ? iswc: string,
    ? ipi: [* string],
    ? ipn: [* string],
    ? isni: [* string],
    ? metadata_language: string,
    ? country_of_origin: string,
    ? language: string,
    ? derived_from: string,
    ? links: { * string => string / [* string] },
  }

metadata_details = 
  {
    name : string,
    image : string / [* string],
    music_metadata_version: 1,
    release_type: "Single" / "Multiple",

    ; Fields that are required if this is a "Single". They are omitted for "Multiple" and should be defined under file_details instead.
    ? artists : [* artist_details],
    ? album_title : string,
    ? track_number: uint,
    ? song_title: string / [* string],
    ? song_duration: string .regexp "^P(?!$)(T(?=\d)(\d+H)?(\d+M)?(\d+S)?)$",  ; iso8601 duration
    ? genres: [1*3 string],
    ? copyright: string,

    ; Fields that are optional for "Single". They are omitted for "Multiple" and may be defined under file_details instead.
    ? contributing_artists : [* artist_details],
    ? series: string,
    ? collection: string,
    ? set: string,
    ? mood: string,
    ? lyrics: string,
    ? lyricists: [* string],
    ? special_thanks: [* string],
    ? visual_artist: string,
    ? distributor: string,
    ? release_date: string,
    ? publication_date: string,
    ? catalog_number: uint,
    ? bitrate: string,
    ? mix_engineer: string,
    ? mastering_engineer: string,
    ? producer: string,
    ? co_producer: string,
    ? featured_artist: artist_details,
    ? recording_engineer: string,
    ? release_version: uint,
    ? parental_advisory: string,
    ? explicit: bool,
    ? isrc: string,
    ? iswc: string,
    ? ipi: [* string],
    ? ipn: [* string],
    ? isni: [* string],
    ? metadata_language: string,
    ? country_of_origin: string,
    ? language: string,
    ? derived_from: string,
    ? links: { * string => string / [* string] },

    files : [* files_details],                                                 ; was optional in CIP-25, required by CIP-60
    ? version: 1 / 2,                                                          ; CIP-25 version
    ? mediaType : string,                                                      ; mediaType for the image. audio goes under files.
    ? description : string / [* string],
  }

label_metadata = { * policy_id => { * asset_name => metadata_details } }

metadata = { 721 : uint => label_metadata }