Requirements schema:DataCatalog cannot hold

[coret]

Our requirements specifiy several properties to be required with schema:DataCatalog. This leads to validation problems, caused by the fact that a Dataset can have an schema:includedInDataCatalog which is of type schema:DataCatalog.

For example:

{
    "@context": "http://schema.org/",
    "@id": "https://data.labs.kadaster.nl/kadaster/bag2",
    "@type": "Dataset",
    ...
    "includedInDataCatalog": {
      "@type": "DataCatalog",
      "@id": "https://data.labs.kadaster.nl",
      "name": "Kadaster Data Science"
    },
    ...
}

This schema:includedInDataCatalog within a schema:Dataset can not be expected to have all datasets of the Datacatalog. Properties like schema:publisher and schema:name are less likely to be present in schema:includedInDataCatalog.

Prososal: change the cardinality and usage of properties to make them optional (after which this should also be change in the SHACL).

4.6.4. DataCatalog attributes

Property	Description	Cardinality	Usage
@id	The HTTP [IRI] of the data catalog.	1	Required
schema:name	The name of the data catalog.	0..1	Recommended
schema:description	A description of the data catalog.	0..1	Recommended
schema:publish	The publisher of the data catalog.	0..1	Recommended
scheme:dataset	The datasets that are contained in the data catalog.	0..n	Recommended

[ddeboer]

If the SHACL needs to change, only change that but leave the requirements as they are to invite providers to submit full data catalog descriptions.

[coret]

Additional cases where the strict requirements hinder validation:

• Dataverse datasetdescriptions are 'missing' a publisher and datasets:
  "includedInDataCatalog":{"@type":"DataCatalog","name":"UCLA Dataverse","url":"https://dataverse.ucla.edu"}

• https://data.bibliotheken.nl/doc/datacatalog is 'missing' datasets.