Contextual entities

Overview

Teaching: 2 min
Exercises: 2 min

Questions

• How can I describe things in the world?

• How can I give details about licenses?

Objectives

• Understand the difference between contextual and data entities

• Add a contextual entity to the RO-Crate

Contextual entities

Entities that we have added under hasPart are considered data entities, while entities only referenced from those are considered contextual entities – they help explain the crate and its content.

You may notice the subtle difference between a data entity that is conceptually part of the RO-Crate and is file-like (containing bytes), while a contextual entity is a representation of a real-life organization that can’t be downloaded: following the URL, we would only get its description. The section contextual entities explores several of the entities that can be added to the RO-Crate to provide it with a context, for instance how to link to authors and their affiliations. Simplifying slightly, a data entity is referenced from hasPart in a Dataset, while a contextual entity is referenced using any other defined property.

Detailing licenses

We have previously declared two different license cross-references. While following the URLs in this case explain the licenses well, it is also best practice to include a very brief summary of contextual entities in the RO-Crate Metadata Document. This is more important if the cross-reference do not use a permalink and may change over time. As a minimum, each referenced entity should have a @type and name property. It is also possible to add url for more information

Add licence entities

Add a contextual entity for each of the two licenses, see the licensing section for details:

Solution

{
    "@id": "https://creativecommons.org/licenses/by-nc-sa/4.0/",
    "@type": "CreativeWork",
    "name": "CC BY-NC-SA 4.0 International",
    "description": "Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International"
},    
{
    "@id": "http://spdx.org/licenses/CC0-1.0",
    "@type": "CreativeWork",
    "name": "CC0-1.0",
    "description": "Creative Commons Zero v1.0 Universal",
    "url": "https://creativecommons.org/publicdomain/zero/1.0/"
},  

An additional exercise is to try to unify the two entites so that both use spdx identifiers, remembering to update the corresponding license cross-references when changing the @id. However, not all licenses have a direct SPDX identifier.

Key Points

• Contextual entities are not considered part of the crate

• Cross-references should be expanded as contextual entities

• It is recommended to provide a human-readable name for licenses