Semantic Model

2025-04-11

Liccium declarations are designed to be both machine-readable and semantically interoperable. Each declaration references a versioned JSON Schema for structural validation, a JSON-LD context for semantic interpretation, and is grounded in a formal OWL ontology. Together these three artefacts define how TDMrep declarations can be understood, validated, and processed consistently across systems.

Schema

The Liccium JSON Schema provides the formal structure for validating declaration payloads. It defines required and optional fields, permitted value ranges, and the overall structure of a declaration including its plugin metadata.

https://w3id.org/liccium/schema/0.3.0.json

Every declaration includes a $schema reference to this URL. Implementations should validate declarations against it before processing or honouring them.

Within the schema, TDMrep preferences are expressed under liccium_plugins.tdmrep:

{
  "tdm-reservation": {
    "type": "integer",
    "enum": [0, 1],
    "description": "1 = TDM rights reserved; 0 = TDM rights not reserved."
  },
  "tdm-policy": {
    "type": "string",
    "format": "uri",
    "description": "URL linking to a TDM policy document."
  }
}

JSON-LD Context

The Liccium JSON-LD context maps declaration fields to their formal semantic identifiers, allowing linked data agents to interpret declarations consistently.

https://w3id.org/liccium/context/0.3.0.json

Each declaration includes a @context reference to this URL. The context maps TDMrep terms to their canonical identifiers under the W3C TDMrep namespace (https://www.w3.org/ns/tdmrep#) and the Liccium ontology namespace (https://w3id.org/liccium/ont/).

Ontology

The Liccium OWL ontology formally defines the properties used in declarations as RDF data properties, including their domain, range, and human-readable descriptions.

https://w3id.org/liccium/context/0.3.0.json

The two TDMrep properties are defined as follows.

tdm-reservation is a datatype property with range xsd:integer, accepting values 0 or 1. A value of 1 means TDM rights are reserved and automated processing including AI training is not permitted without authorisation from the rightsholder. A value of 0 means TDM rights are not reserved and use is permitted without contacting the rightsholder.

tdm-policy is a datatype property with range xsd:anyURI. It links to a policy document – human- or machine-readable – specifying the conditions under which content may be used for TDM purposes. It is only meaningful when tdm-reservation is set to 1.

Both properties have domain liccium:Declaration, meaning they are properties of a signed declaration bound to an ISCC fingerprint – not properties of the content file itself.