Making a metadata descriptor

Estimated time: 4 minutes

Overview

Questions

• Which RO-Crate version is used?
• How can the crate self-identify as an RO-Crate?

Objectives

• Add the first entity to the JSON-LD @graph
• Indicate the version of RO-Crate

RO-Crate Metadata descriptor

---

Next, we’ll add another entity to the @graph array has the @id value of ro-crate-metadata.json to describe the JSON file itself:

JSON

{
    "@id": "ro-crate-metadata.json",
    "@type": "CreativeWork",
    "conformsTo": {"@id": "https://w3id.org/ro/crate/1.2"},
    "about": {"@id": "./"}
}

This required entity, known as the RO-Crate Metadata Descriptor, helps this file self-identify as an RO-Crate Metadata Document, which is conforming to (conformsTo) the RO-Crate specification version 1.2. Notice that the conformsTo URL corresponds to the @context URL version-wise, but they have two different functions. The context brings the defined terms into the metadata document, while the conformance declares which RO-Crate conventions of using those terms are being followed.

Callout

Adding entities to the JSON array

Because we’re adding incrementally to the @graph array. It is important to remember the comma , between each entity, except for the final entity in the JSON array; and likewise for the properties within the JSON object for each entity. This is an artefact of the strict JSON file format rules to simplify parsing. The order of the entities within the @graph JSON-LD array and the order of the keys within a JSON object is not significant. The graph content is given by the @id cross-references.

You will add a comma here between the ro-crate-metadata.json entity, and the root data entity.

Callout

RO-Crate versions

This tutorial is written for RO-Crate 1.2, the RO-Crate website will list the current specification version – RO-Crates can generally be upgraded to newer versions following semantic versioning conventions, but check the change log for any important changes. The next development version of the specification, indicated with a -DRAFT status, may still be subject to changes and should only be used with caution.

Key Points

• The RO-Crate Metadata Descriptor describes the JSON-LD file itself
• RO-Crate specifications are versioned
• The version of RO-Crate is indicated using the conformsTo property