Content Credential Schema

Every schema begins with a unique assertion type identifier—a URI that namespaces the claim. This ensures validators can unambiguously interpret the data. For example, c2pa.org/assertions/creative-work identifies a schema describing authorship metadata. The type declaration prevents collision between schemas from different standards bodies and allows validators to load the correct parsing logic.

A schema enforces mandatory fields that must be present for a credential to be considered valid. These typically include:

• Creator identity: A reference to an identity assertion or X.509 certificate
• Timestamp: When the assertion was generated
• Content hash: The cryptographic fingerprint of the asset at assertion time Without these fields, a validator engine will reject the credential as malformed.

Each field in a schema carries a strict data type definition—string, integer, URI, date-time, or nested object. This type enforcement prevents ambiguity during serialization and deserialization. For instance, a creationDate field must conform to ISO 8601 format, while a softwareAgent field expects a URI pointing to a registered software identifier. Type mismatches trigger validation failures.

Schemas often bind to established ontologies like W3C PROV or Dublin Core to provide semantic meaning. A field labeled dc:creator inherits the Dublin Core definition of 'an entity primarily responsible for making the resource.' This ontological grounding allows validators to reason about provenance across different schema implementations and enables cross-domain interoperability.

Well-designed schemas include extension points for proprietary or domain-specific data without breaking core validation. The C2PA specification allows custom assertion types to be registered under private namespaces. A schema might define a base set of required fields while permitting optional vendor-specific metadata—such as camera serial numbers or GPS coordinates—within a defined extension block.

Schemas carry explicit version identifiers to manage evolution over time. A validator encountering schema version 1.2 knows which fields to expect and can apply migration rules if it only understands version 1.1. This versioning contract ensures that credentials signed with newer schemas remain verifiable by older validators, preventing fragmentation in the provenance ecosystem.

A cryptographically signed claim linking content to a verified real-world identity. The schema defines how to reference X.509 certificates and W3C Verifiable Credentials.

• Identity binding: Maps a public key to a verified organization or individual
• Certificate chain: Must include the full path to a trusted root CA
• Privacy consideration: Supports selective disclosure to reveal only necessary identity attributes

Describes a specific operation performed on content, such as cropping, resizing, or AI generation. The schema standardizes how edit operations are documented.

• Required parameters: action type, software agent identifier, timestamp
• Standardized vocabulary: Uses controlled terms like c2pa:cropped, c2pa:resized, c2pa:color_adjusted
• AI disclosure: Must flag if generative AI was used, including model identifier and prompt hash