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SLD-1: Token Standard

Status
Draft

The SLD-1 is a standard for Non-Fungible Tokens on the Internet Computer based on the ICRC-1 standard.

Data

account

A principal can have multiple accounts. Each account of a principal is identified by a 32-byte string called subaccount. Therefore an account corresponds to a pair (principal, subaccount).

The account identified by the subaccount with all bytes set to 0 is the default account of the principal.

type Subaccount = blob;
type Account = record { owner : principal; subaccount : opt Subaccount; };

Methods

sld1_name

Returns the name of the token (e.g., ICSnakes).

icrc1_name : () -> (text) query;

sld1_symbol

Returns the symbol of the token (e.g., SNAKE).

sld1_symbol : () -> (text) query;

sld1_metadata

Returns the list of metadata entries for this ledger.
See the "Metadata" section below.

type Value = variant { Nat : nat; Int : int; Text : text; Blob : blob };

sld1_metadata : () -> (vec record { text; Value }) query;

sld1_total_supply

Returns the total number of tokens on all accounts except for the minting account.

sld1_total_supply : () -> (nat) query;

icrc1_minting_account

Returns the minting account if this ledger supports minting and burning tokens.

sld1_minting_account : () -> (opt Account) query;

sld1_balance_of

Returns the balance of the account given as an argument.

sld1_balance_of : (Account) -> (nat) query;

sld1_owner_of

Returns the owner of the token id given as an argument.

sld1_owner_of : (TokenId) -> (opt Account) query;

sld1_tokens

Returns token ids for the page given as an argument, burned tokens are not included.

sld1_tokens: (nat) -> (vec TokenId) query;

sld1_tokens_of

Returns token ids for the account and page given as an argument.

sld1_tokens_of: (Account, nat) -> (vec TokenId) query;

sld1_metadata_of

Returns the list of metadata entries for this token id.
See the "Metadata" section below.

sld1_metadata_of: (TokenId) -> (opt vec record { text; Value }) query;

sld1_transfer

Transfers token_id from account record { of = caller; subaccount = from_subaccount } to the to account.

type TransferArgs = record {
    from_subaccount: opt Subaccount;
    to: Account;
    token_id: TokenId;
    memo: opt blob;
    created_at_time: opt nat64;
};

type TransferError = variant {
    NotFound;
    NotOwner;
    TooOld;
    CreatedInFuture : record { ledger_time: nat64 };
    TemporarilyUnavailable;
    GenericError: record {
        error_code: nat;
        message: text
    };
};

icrc1_transfer : (TransferArgs) -> (variant { Ok: nat; Err: TransferError; });

The memo parameter is an arbitrary blob that has no meaning to the ledger. The ledger SHOULD allow memos of at least 32 bytes in length.

The created_at_time parameter indicates the time (as nanoseconds since the UNIX epoch in the UTC timezone) at which the client constructed the transaction. The ledger SHOULD reject transactions that have created_at_time argument too far in the past or the future, returning variant { TooOld } and variant { CreatedInFuture = record { ledger_time = ... } } errors correspondingly.

The result is either the transaction index of the transfer or an error.

icrc1_supported_standards

Returns the list of standards this ledger implements. See the "Extensions" section below.

sld1_supported_standards : () -> (vec record { name : text; url : text }) query;

The result of the call should always have at least one entry,

record { name = "SLD-1"; url = "https://github.com/slide-computer/slide-token" }

Extensions

The base standard intentionally excludes some ledger functions essential for building a rich NFT ecosystem, for example:

  • Reliable transaction notifications for smart contracts.
  • The block structure and the interface for fetching blocks.
  • Pre-signed transactions.

The standard defines the sld1_supported_standards endpoint to accommodate these and other future extensions. This endpoint returns names of all specifications (e.g., "SLD-2" or "DIP-721-V2") implemented by the ledger.

Metadata

A ledger can expose metadata to simplify integration with wallets and improve user experience. The client can use the sld1_metadata method to fetch the metadata entries. All the metadata entries are optional.

Key format

The metadata keys are arbitrary Unicode strings and must follow the pattern <namespace>:<key>, where <namespace> is a string not containing colons. Namespace sld1 is reserved for keys defined in this standard.

Standard metadata entries

Key Example value Semantics
sld1:symbol variant { Text = "XTKN" } The token currency code (see ISO-4217). When present, should be the same as the result of the sld1_symbol query call.
sld1:name variant { Text = "Test Token" } The name of the token. When present, should be the same as the result of the sld1_name query call.
sld1:logo variant { Text = "https://uscpd-maaaa-aaaak-abvqa-cai.ic0.app/logo.svg" } The logo of the token.

Minting account

The minting account is a unique account that can create new tokens and acts as the receiver of burnt tokens.

Transfers from the minting account act as mint transactions depositing fresh tokens on the destination account. Mint transactions have no fee.

Transfers to the minting account act as burn transactions, removing tokens from the token supply.

Minting and burning NFT tokens is out of the scope of this standard, see SLD-4 and SLD-5 for standards regarding this.

Textual representation of accounts

See the canonical textual format defined in ICRC-1