Basic Concepts¶

The core idea is that an OO-LD document is always both a valid JSON Schema and a reference-able JSON-LD remote context (not a JSON-LD document). In this way a complete OO-LD class / schema hierarchy is usable by JSON Schema-only and JSON-LD-only tools, while OO-LD-aware tools add features on top (UI autocomplete for IRI fields, SHACL shape or JSON-LD frame generation, ...).

A minimal example:

{
  "$schema": "https://oo-ld.github.io/oold-schema/latest/meta/oold-meta-schema.json",
  "$id": "Minimal.schema.json",
  "@context": {
    "schema": "http://schema.org/",
    "name": "schema:name"
  },
  "title": "Minimal",
  "type": "object",
  "properties": {
    "name": { "type": "string", "description": "Name of the thing" }
  }
}

You can explore this in the interactive playground.

Schemas vs. instances¶

A schema is consumed as a JSON-LD remote context (referenced from an instance's @context), never expanded as a document. An instance is a JSON-LD document and is processed as such. This asymmetry is what lets one document act both as a JSON Schema $ref target and as a JSON-LD context.

Inheritance¶

A class B extends a class A by referencing it in both allOf (so validators apply A's rules to B instances) and @context (so JSON-LD resolves A's term mappings); B instances are therefore valid A instances. See Basic Concepts in the specification for the inheritance diagram and the exact consumption rules. Building types from multiple independent schemas is covered in Composition.

You can read how this is implemented in OpenSemanticWorld/Lab in the introduction and schema documentation draft.