Output Features

The output features that don't affect the actual unlocking and hence ownership, are called Output Features.

Metadata

The Metadata Feature makes it possible to store any data in outputs. Smart contract requests make use of it to encode the actual request call data that is only interpreted on L2.

Of course, there is a limit on how much data one can store in an output, as outputs are part of transactions that have a limited size. Anyway, bigger data can always be sliced up into chunks to be stored in outputs.

Sender

The Sender Feature allows to define a sender address directly inside an output. The protocol validates whether the address was actually signed in the transaction that created the output or not. Smart contract chains identify the sender account of an on-ledger request based on the information present in the Sender Feature of the output.

The combination of the Sender Feature with the Metadata Feature makes it possible to implement data oracles in the ledger with verified sources.

Issuer

The Issuer Feature follows the same address verification logic as the Sender Feature, but it is only available for NFTs. Upon NFT minting, one might attach the issuer identity to the token if ownership of the issuer address is proved by unlocking it in the same transaction. Artists that disclose their issuer identities off-chain protect buyers and traders from fakes.

Tag

A Tag Feature is a small piece of data intended to be used as an indexation tag for the output by custom applications built around the network. It becomes possible to map data (Metadata Feature) stored in the ledger by a specific party (Sender Feature) for a specific purpose (Tag Feature).

To read more about outputs, the Stardust ledger and tokenization concepts check out TIP-18.