Singletons
Understanding singleton tokens in the UTXO model
Overview
In the UTXO model, a token issued with a quantity of exactly one unit is referred to as a singleton token. Singleton tokens can be used to emulate long-lived accounts similar to those found in Waves, Ethereum Classic, etc.
A transaction that spends an old box with the singleton token and creates a new one can be controlled by the script of the old box, requiring the new box to have certain characteristics (such as a specific script or amount). This allows a smart account, marked with the token, to exist and alter its state as dictated by the smart account contract through a chain of transactions.
Oracle Example
One specific example of a singular token is an oracle. For instance, a token can be created to act as an ERG/EUR exchange rates oracle.
A box that contains this token would encode the exchange rate in a specific register. Since the oracle is a long-lived account, contracts can know the oracle token identifier beforehand and refer to it.
Key Benefits
- Long-lived accounts in UTXO model
- Controlled state transitions
- Predictable token identifiers
- Smart contract integration
Technical Details
Token Characteristics
- Exactly one unit quantity
- Unique token identifier
- Persistent across transactions
- Script-controlled state changes
Use Cases
- Oracle data feeds
- Smart account management
- Long-lived contract states
- Identity and reputation systems
Implementation
Singleton tokens are implemented by creating a token with a quantity of exactly 1. The token ID becomes the unique identifier for the singleton, and the containing box's script controls how the singleton can be spent and recreated.
This pattern allows for complex state machines and long-lived entities within the UTXO model, bridging the gap between account-based and UTXO-based blockchain architectures.