The focus of an RO-Crate

In addition to simple data packaging, Crates may have a “main” entry point or topic (referenced with a singleton mainEntity property), or function as a bundle of one or more Contextual Entities referenced via the mentions property.

Crates with a “main entity”

An RO-Crate may have a single main entity that is considered the point, or focus of the crate.

Crates with a data entity as mainEntity

In the Workflow RO-Crate profile, where the mainEntity has a compound type ["File", "SoftwareSourceCode", "ComputationalWorkflow"], the use of mainEntity singles-out the workflow file from supporting files.

{
    "@id": "./",
    "@type": "Dataset",
    "name": "Example Workflow",
    "description": "An example workflow RO Crate",
    "license": "Apache-2.0",
    "mainEntity": {
      "@id": "example_workflow.cwl"
    },
    "hasPart": [
      {
        "@id": "example_workflow.cwl"
      },
      {
        "@id": "diagram.svg"
      },
      {
        "@id": "README.md"
      }
    ]
}

Crates with a contextual entity as mainEntity

The focus of the RO-Crate may be a description of a Contextual Entity, for example in an RO-Crate used in a repository or encyclopedia where a RepositoryObject bundles together images and other files, but the main focus of the RO-Crate is on describing a person.

{
    "@id": "./",
    "@type": ["Dataset", "RepositoryObject"],
    "name": "Reibey, Mary (1777 - 1855)",
    "mainEntity": {
        "@id": "https://en.wikipedia.org/wiki/Mary_Reibey"
    }
    "hasPart" : [
        {"@id": "photo1.jpg"},
        {"@id": "photo2.jpg"}
    ]
}

{
    "@id": "https://en.wikipedia.org/wiki/Mary_Reibey",
    "@type": "Person",
    "name": "Mary Reibey",
    "description": "Mary Reibey née Haydock (12 May 1777 – 30 May 1855) was an English-born merchant, shipowner and trader ..."
}

Crates which describe Contextual Entities

RO-Crates may describe Contextual Entities which are linked to the Root Dataset via mentions relationships.

For example, RO-Crates can be used as containers for schema.org-style vocabularies (here also extending the RO-Crate JSON-LD context to define the namespace for txc:):

{ "@context": [
    "https://w3id.org/ro/crate/1.2-DRAFT/context",
    {"txc": "https://purl.archive.org/language-data-commons/terms#"}
  ],
  "@graph": [
    {
      "@id": "ro-crate-metadata.json",
      "@type": "CreativeWork",
      "description": "RO-Crate Metadata File Descriptor (this file)",
      "conformsTo": {"@id": "https://w3id.org/ro/crate/1.2-DRAFT"},
      "about": {"@id": "./"}
    },
    {
      "@id": "./",
      "@type": "Dataset",
      "description": "This is an experimental language data ontology based on OLAC terms for use in the ATAP and LDaCA projects",
      "hasPart": [],
      "name": "Language Data Ontology",
      "mentions": ["txc:Annotation", "txc:CollectionEvent"]
    },
    {
      "@id": "txc:Annotation",
      "@type": "rdfs:Class",
      "name": "Annotation",
      "sameAs": "http://www.language-archives.org/REC/type-20020628.html#annotation",
      "rdfs:comment": "The resource includes information which annotates some other linguistic record.",
      "rdfs:label": "Annotation",
      "rdfs:subClassOf": {
        "@id": "schema:CreativeWork"
      }
    },
    {
      "@id": "txc:CollectionEvent",
      "@type": "rdfs:Class",
      "name": "CollectionEvent",
      "rdfs:comment": "A description of an event at which one or more PrimaryTexts were captured, e.g. as video or audio",
      "rdfs:label": "CollectionEvent",
      "rdfs:subClassOf": [
        {
          "@id": "schema:Event"
        },
        {
          "@id": "schema:CreateAction"
        }
      ]
    }
  ]
}    

The following example shows both a mainEntity which is a Data Entity and a Contextual Entity which is a test suite (#test1).

        {
            "@id": "./",
            "@type": "Dataset",
            "name": "sort-and-change-case",
            "description": "sort lines and change text to upper case",
            "license": "Apache-2.0",
            "mainEntity": {
                "@id": "sort-and-change-case.ga"
            },
            "mentions": [ {"@id": "#test1"} ],
            "hasPart": [
                {
                    "@id": "sort-and-change-case.ga"
                },
                {
                    "@id": "test/test1/sort-and-change-case-test.yml"
                }
            ]
        },
		    {
            "@id": "#test1",
            "name": "test1",
            "@type": "TestSuite",
            "instance": [
                {"@id": "#test1_1"}
            ],
            "definition": {"@id": "test/test1/sort-and-change-case-test.yml"}
        },
        {
            "@id": "#test1_1",
            "name": "test1_1",
            "@type": "TestInstance",
            "runsOn": {"@id": "#jenkins"},
            "url": "http://example.org/jenkins",
            "resource": "job/tests/"
        },
        {
            "@id": "test/test1/sort-and-change-case-test.yml",
            "@type": [
                "File",
                "TestDefinition"
            ],
            "conformsTo": {"@id": "#planemo"}
        },
        {
            "@id": "#jenkins",
            "@type": "TestService",
            "name": "Jenkins",
            "url": {"@id": "https://www.jenkins.io"}
        },
        {
            "@id": "#planemo",
            "@type": "SoftwareApplication",
            "name": "Planemo",
            "url": {"@id": "https://github.com/galaxyproject/planemo"},
            "version": ">=0.70"
        }