# Schema

## Schema

This struct represents an on-chain Schema that Attestations can conform to.

`registrant`: The address that registered this schema.

`revocable`: Whether Attestations that adopt this Schema can be revoked.

`dataLocation`: Where `Schema.data` is stored. See `DataLocation.DataLocation`.

`maxValidFor`: The maximum number of seconds that an Attestation can remain valid. 0 means Attestations can be valid forever. This is enforced through `Attestation.validUntil`.

`hook`: The `ISPHook` that is called at the end of every function. 0 means there is no hook set. See `ISPHook`.

`timestamp`: When the schema was registered. This is automatically populated by `_register(...)`.

`data`: The raw schema that `Attestation.data` should follow. Since there is no way to enforce this, it is a `string` for easy readability.

```solidity
struct Schema {
  address registrant;
  bool revocable;
  enum DataLocation dataLocation;
  uint64 maxValidFor;
  ISPHook hook;
  uint64 timestamp;
  string data;
}
```