# LBRY Claim Metadata Schema

The schema defines the structure of the data that is stored in claims in the LBRY blockchain. It has several goals:

- **Extensibility**. The schema could grow to encompass thousands of fields for dozens of types of content. It should be easy to modify the schema while maintaining backward compatibility. Blockchain data is permanent and cannot be migrated, so any selected data structure will have to be maintained forever.
- **Compactness**. Blockchain space is expensive. Data should be stored as compactly  as possible.
- **Cross-language Interop**. These definitions will be used by many projects written in different languages.


## [Claim](https://github.com/lbryio/lbryschema/blob/master/lbryschema/proto/claim.proto)

A `Claim` is the toplevel schema for everything that is published to the blockchain.

```protobuf
message Claim {
    enum Version {
        UNKNOWN_VERSION = 0;
        _0_0_1 = 1;
    }
    required Version version = 1;

    enum ClaimType {
        UNKNOWN_CLAIM_TYPE = 0;
        streamType = 1;
        certificateType = 2;
    }
    required ClaimType claimType = 2;

    optional Stream stream = 3;
    optional Certificate certificate = 4;
    optional Signature publisherSignature = 5;
}
```


## Content

### [Stream](https://github.com/lbryio/lbryschema/blob/master/lbryschema/proto/stream.proto)

All content claims have a Stream field, which includes the content-specific information (e.g. a description of the content, instructions for downloading the content, etc).

```protobuf
message Stream {
    enum Version {
        UNKNOWN_VERSION = 0;
        _0_0_1 = 1;
    }
    required Version version = 1;

    required Metadata metadata = 2;
    required Source source = 3;
}
```

### [Metadata](https://github.com/lbryio/lbryschema/blob/master/lbryschema/proto/metadata.proto)

`Metadata` provides information about a piece of content, such as the title, description, and price.

```protobuf
message Metadata {
    enum Version {
        UNKNOWN_VERSION = 0;
        _0_0_1 = 1;
        _0_0_2 = 2;
        _0_0_3 = 3;
        _0_1_0 = 4;
    }
    required Version version = 1;

    enum Language {
        UNKNOWN_LANGUAGE = 0;
        en = 1;
    }
    required Language language = 2;

    required string title = 3;
    required string description = 4;
    required string author = 5;
    required string license = 6;
    required bool nsfw = 7;

    optional Fee fee = 8;

    optional string thumbnail = 9;
    optional string preview = 10;
    optional string licenseUrl = 11;
}
```

### [Fee](https://github.com/lbryio/lbryschema/blob/master/lbryschema/proto/fee.proto)

A `Fee` defines the prices for accessing a piece of content.

```protobuf
message Fee {
    enum Version {
        UNKNOWN_VERSION = 0;
        _0_0_1 = 1;
    }
    required Version version = 1;

    enum Currency {
        UNKNOWN_CURRENCY = 0;
        LBC = 1;
        BTC = 2;
        USD = 3;
    }
    required Currency currency = 2;

    required bytes address = 3;
    required float amount = 4;
}
```

### [Source](https://github.com/lbryio/lbryschema/blob/master/lbryschema/proto/source.proto)

A `Source` contains information on how to download a stream. Only the LBRY data network is supported at the moment, but other sources may be added in the future.

```protobuf
message Source {
    enum Version {
        UNKNOWN_VERSION = 0;
        _0_0_1 = 1;
    }
    required Version version = 1;

    enum SourceTypes {
        UNKNOWN_SOURCE_TYPE = 0;
        lbry_sd_hash = 1;
    }
    required SourceTypes sourceType = 2;

    required bytes source = 3;
    required string contentType = 4;
}
```

## Channels

Channels are the identity mechanism in LBRY. They are constructed out of Certificates and Signatures. Both utilize a KeyType:

```protobuf
enum KeyType {
    UNKNOWN_PUBLIC_KEY_TYPE = 0;
    NIST256p = 1;
    NIST384p = 2;
    SECP256k1 = 3;
}
```

### [Certificate](https://github.com/lbryio/lbryschema/blob/master/lbryschema/proto/certificate.proto)

Creating a channel involves making a `certificateType` claim. This claim contains the public key for a channel. It must include a Certificate field:

```protobuf
message Certificate {
    enum Version {
        UNKNOWN_VERSION = 0;
        _0_0_1 = 1;
    }
    required Version version = 1;

    required KeyType keyType = 2;
    required bytes publicKey = 4;
}
```


### [Signature](https://github.com/lbryio/lbryschema/blob/master/lbryschema/proto/signature.proto)

Publishing a claim to a channels simply means that the claim is signed using the private key for a channel. This is done by including a Signature field in a Claim:

```protobuf
message Signature {
    enum Version {
        UNKNOWN_VERSION = 0;
        _0_0_1 = 1;
    }
    required Version version = 1;

    required KeyType signatureType = 2;
    required bytes signature = 3;
    required bytes certificateId = 4;
}
```