Requirements for Datasets

This document is a working draft.

1. Introduction

This section is non-normative.

To enable datasets to be found and used, they must be published according to a well-documented, shared and machine-readable publication model.

This document describes such a model and its rules. When publishers make their datasets adhere to these rules, they enable consumers – both humans and machines – to use the published data in new and better ways.

The requirements prescribe the metadata that publishers should provide with their data. This metadata tells consumers:

what the dataset is called and under what license it is published (§ 4.2 Dataset information);
which organization has published the dataset (§ 4.3 Organization information);
where the data can be found (§ 4.4 Distributions).

1.1. Audience

This document is mainly geared towards two groups of readers.

Digital heritage collection managers can follow the requirements in this document to make their published datasets findable and usable, for instance through Google Dataset Search and the NDE Registry.

Suppliers of collection management systems can implement these requirements in their software to help collection managers using it to publish datasets in the correct format. These requirements are scoped to the online publication output of collection management systems; they do not prescribe how those systems should store data internally.

1.2. Context

While focused on digital heritage institutions in The Netherlands, this document is based on broader, international best practices for publishing datasets, including [DWBP-UCR], [DWBP] and [LD-BP].

These requirements incorporate a previous publication model, which provides more background on choices made here.

1.3. Code examples

RDF code examples are in the [SCHEMA-ORG] vocabulary, serialized as [JSON-LD].

While other vocabularies, such as [VOCAB-DCAT-2] can also be used, Schema.org has the advantage that it’s better picked up by search engines, improving findability, one of the main goals of publishing datasets on the web.

2. Definitions

Dataset

The description of a collection of data. A set of metadata that includes the dataset’s name and publisher. The data objects themselves are not part of the dataset proper but provided in its distributions.

For example: imagine a dataset of Van Gogh paintings called ‘Sunflowers’, which is published by the Van Gogh Museum under a specific license. These are all part of the dataset. The dataset also tells us the URLs of distributions where we can download or query the data. If we consult the data provided by one of these distributions, we’ve left the sphere of the dataset proper. That is to say, the data itself, which may include descriptions of paintings, persons and places, are not properties of the dataset.

Data catalog

A collection of datasets.

Distribution

A channel through which a dataset is available, for example a CSV file download or a SPARQL endpoint.

Application Programming Interface (API)

TODO

Machine-readability

TODO

Publisher

An individual or organization that provides one or more datasets.

is this a good translation for ‘bronhouder’? And add examples. This would probably be ‘heritage institution’ in DERA.

Consumer

On organization or an individual that uses one or more datasets that are provided by a publisher.

add examples

3. Conceptual model

The model consists of four resource types: organizations publish datasets, which are available in distributions. Optionally, the datasets are grouped in data catalogs.

4. Requirements

4.1. Available in RDF

For machine-readable access to data, it needs to be published in an RDF format. RDF formats include [JSON-LD], [N3] and [Turtle].

Publishers MUST make their dataset description available in RDF.

Both the Schema.org and DCAT vocabularies MAY be used; Schema.org is recommended.

Google recommends including the JSON-LD directly in the HTML source of web pages.

So, on your organization’s web page, for instance www.kb.nl, include:

<html>
  <head>
    <title>Koninklijke Bibliotheek</title>
    <script type="application/ld+json">
      {
        "@context": "https://schema.org/",
        "@type": "Organization",
        "@id": "https://www.kb.nl",
        "name": "Koninklijke Bibliotheek"
      }
    </script>
  </head>
  <body>
    Here continues the web page of the organization...
  </body>
</html>

4.1.1. Durable identifiers

Consumers want to refer to datasets. They prefer to do so by linking to them.

Therefore, publishers must maintain a permanent and unique identifier for each dataset. Publishers must use HTTP IRIs as identifiers.

4.1.2. Information remains available

Datasets will be used by all kinds of consumers and their systems. For stability, users must be able to trust that the datasets will remain available so they can be consulted in the future.

Therefore, publishers must ensure information remains available in the future.

4.2. Dataset information

Consumers want to consult information about the dataset to decide whether and how they want to use its data. This information answers user questions such as:

What is the name of the dataset?
What is the dataset about? What kind of data does the dataset contain?
How recent is the data? When was the dataset last published?
How can I use the data? Are there any restrictions? Under which license is the data published?
Where can I get the data? In what formats?

4.2.1. Basic information

Publishers MUST include basic information about the dataset, at the very minimum its HTTP [IRI] and name.

Basic dataset information:

{
  "@context": "https://schema.org/",
  "@type": "Dataset",
  "@id": "http://data.bibliotheken.nl/doc/dataset/rise-alba",
  "name": "Alba amicorum van de Koninklijke Bibliotheek"
}

4.2.2. License

Publishers MUST make known under which license the dataset can be used. This SHOULD be an open license that allows the data to used by consumers, for example one of the Creative Commons licenses.

Specify a license for the dataset:

{
  "@context": "https://schema.org/",
  "@type": "Dataset",
  "license": "http://creativecommons.org/publicdomain/zero/1.0/"
}

4.2.3. Creation, publication and modification dates

Publishers SHOULD make known when the dataset description was originally created, published and when it was last updated.

Specify dataset description dates:

{
  "@context": "https://schema.org/",
  "@type": "Dataset",
  "dateCreated": "2019-04-14",
  "datePublished": "2019-05-21",
  "dateModified": "2019-08-15"
}

4.2.4. Version

A dataset description may change over time. Consumers, such as researchers, may want to determine which information was valid at a certain moment.

Therefore, publishers SHOULD not only publish the current version of the dataset description, but keep historical versions accessible to users.

It is up to the publisher to determine when to publish new versions.

4.2.5. More information

If more information is available, publishers SHOULD add it.

More information about the dataset.

{  "@context": "https://schema.org/",  "@type": "Dataset",  "description": "Alba amicorum van de Koninklijke Bibliotheek, een dataset gedefinieerd voor het Europeana Rise of Literacy project.",  "url": "https://www.kb.nl/bronnen-zoekwijzers/kb-collecties/moderne-handschriften-vanaf-ca-1550/alba-amicorum",  "keywords": [    "alba amicorum"  ]}

See § 4.6.1 Dataset attributes for an overview of attributes.

4.3. Organization information

Users want to know where the dataset came from (provenance). Providing information about the organization behind the dataset (the publisher) answers user questions such as:

Which organization has published this dataset? How reliable and credible does that make the dataset?
How can I contact the organization for questions or feedback?

Therefore, publishers must publish basic information about the organization. At the least, the organization’s name and HTTP IRI must be provided.

An organization description:

{
  "@context": "https://schema.org/",
  "@type": "Organization",
  "@id": "https://www.kb.nl",
  "name": "Koninklijke Bibliotheek",
  "alternateName": "KB"
}

See § 4.6.2 Organization attributes for a full overview of organization attributes.

4.3.1. Dataset publisher

The organization data is then included as the dataset’s publisher:

A dataset with a publisher. The publisher has some optional attributes.

{
  "@context": "https://schema.org/",
  "@type": "Dataset",
  "publisher": {
    "@type": "Organization",
    "@id": "https://www.kb.nl",
    "name": "Koninklijke Bibliotheek",
    "alternateName": "KB"
  }
}

4.4. Distributions

Consumers that are interested in a dataset should be able to access the data in it. Distributions tell consumers where and how they can get the data.

Therefore, publishers SHOULD add at least one distribution. Each distribution MUST have at least a MIME format and the URL where the distribution can be accessed.

Distributions can be data dumps in RDF or some other format such as CSV, live SPARQL endpoints, OAI-PMH endpoints or other APIs.

A minimal definition of a SPARQL endpoint distribution. In the Schema.org vocabulary, each type of distribution is called a DataDownload, even if it is a query endpoint.

{
  "@context": "https://schema.org/",
  "@type": "DataDownload",
  "encodingFormat": "application/sparql-query",
  "contentUrl": "http://vocab.getty.edu/sparql"
}

The distributions are then included under the distribution attribute with the dataset.

A dataset with two distributions.

{
  "@context": "https://schema.org/",
  "@type": "Dataset",
  "distribution": [
    {
      "@id": "http://vocab.getty.edu/aat/sparql",
      "@type": "DataDownload",
      "encodingFormat": "application/sparql-query",
      "contentUrl": "http://vocab.getty.edu/sparql"
    },
    {
      "@type": "DataDownload",
      "encodingFormat": "application/ld+json",
      "contentUrl": "http://data.bibliotheken.nl/id/dataset/rise-alba.json"
    },
    {
      "@type": "DataDownload",
      "encodingFormat": "text/csv",
      "contentUrl": "https://example.com/data.csv"
    }
  ]
}

See § 4.6.3 Distribution attributes for a full overview.

TODO Elaborate (and give examples of) the types of distribution (in schema:name), like SPARQL-endpoint, OAI-PMH-endpoint, LDF-endpoint, Data dump, Opensearch API. Or introduce proprietary property for the type (might be better the using the free-format name).

4.4.1. Developer documentation

If the distribution is non-standard API, publishers MUST publish human-readable documentation on how to use that API and link to the documentation URL in the schema:usageInfo attribute:

A custom API with a link to the documentation. A minimal definition of a SPARQL endpoint distribution.

{
  "@context": "https://schema.org/",
  "@type": "DataDownload",
  "encodingFormat": "application/json",
  "contentUrl": "https://example.com/custom-json-api",
  "usageInfo": "https://example.com/custom-json-api/docs"
}

4.5. Data catalog

A data catalog provides consumers with a complete overview of available datasets, which improves discoverability.

Therefore, publishers SHOULD provide a catalog.

A catalog of available datasets:

{
  "@context": "https://schema.org/",
  "@type": "DataCatalog",
  "@id": "http://data.bibliotheken.nl/id/datacatalog",
  "name": "Linked Data KB",
  "description": "Alle linked data zoals beschikbaar gesteld door de Koninklijke Bibliotheek.",
  "publisher": {
    "@type": "Organization",
    "@id": "https://www.kb.nl/"
    "name": "Koninklijke Bibliotheek",
  },
  "dataset": [
    {
      "@type": "Dataset",
      "@id": "http://data.bibliotheken.nl/id/dataset/rise-alba",
      ...
    }, 
    { 
      ...
    }
  ]
}

See § 4.6.4 DataCatalog attributes for a full overview of catalog attributes.

4.6. Overview of attributes

This is an overview of required and recommended attributes.

4.6.1. Dataset attributes

schema:Dataset properties
Property	Description	Cardinality	Usage
@id	The HTTP [IRI] of the dataset.	1	Required
schema:name	See § 4.2.1 Basic information	1	Required
schema:description	See § 4.2.1 Basic information.	0..1	Recommended
schema:publisher	The publisher of the dataset.	1	Required
schema:license	See § 4.2.2 License.	1	Required
schema:distribution	See § 4.4 Distributions.	0..n	Recommended
schema:creator	The owner of the dataset.	0..1	Recommended
schema:dateCreated	See § 4.2.3 Creation, publication and modification dates.	0..1	Recommended
schema:datePublished	See § 4.2.3 Creation, publication and modification dates.	0..1	Recommended
schema:dateModified	See § 4.2.3 Creation, publication and modification dates.	0..1	Recommended
schema:version	See § 4.2.4 Version.	0..1	Recommended
schema:mainEntityOfPage	URL of a webpage where the dataset is described.	0..1	Recommended
schema:inLanguage	Language or languages in which the dataset is available. Use one of the language codes from the [BCP47], such as "nl-NL".	0..n	Recommended
schema:isBasedOnUrl	The URL of dataset this dataset is based on.	0..1	Recommended
schema:citation	A citation or reference for the dataset.	0..1	Recommended
schema:genre	The genre or genres which describe the dataset.	0..n	Recommended
schema:keywords	One or more keyword which describe the dataset.	0..n	Recommended
schema:spatialCoverage	Indicates the place(s) which are the focus of the dataset.	0..1	Recommended
schema:temporalCoverage	Indicates the period that the dataset applies to.	0..1	Recommended
schema:includedInDataCatalog	The HTTP [IRI] of the data catalog(s) that the dataset belongs to.	0..1	Recommended

4.6.2. Organization attributes

schema:Organization properties
Property	Description	Cardinality	Usage
@id	The HTTP [IRI] of the organization.	1	Required
schema:name	The organization’s full name.	1	Required
schema:alternateName	Alternative names such as an abbreviation that the organization is known under.	0..n	Recommended
schema:sameAs	Links to the organization in other databases.	0..n	Recommended

4.6.3. Distribution attributes

schema:DataDownload properties
Property	Description	Cardinality	Usage
schema:contentUrl	The URL where the distribution can be directly accessed.	1	Required
schema:encodingFormat	The distribution’s MIME format, for example `application/sparql-query` for a SPARL endpoint or `application/ld+json` for a data dump serialized as JSON-LD. See [IANA-MEDIA-TYPES] and MDN-reference for more information.	1..n	Required
schema:name	Name of the distribution, depicting the type of distribution.	0..1	Recommended
schema:description	A description of the the distribution.	0..1	Recommended
schema:datePublished	Date (or datetime) the distribution was published.	0..1	Recommended
schema:dateModified	Date (or datetime) the distribution was last modified.	0..1	Recommended
schema:inLanguage	Language or languages in which the dataset is available. Use one of the language codes from the [BCP47], such as "nl-NL".	0..1	Recommended
schema:license	See § 4.2.2 License.	0..1	Recommended
schema:contentSize	A measure indicating the size of the distribution.	0..1	Recommended
schema:usageInfo	A link to the API documentation; see § 4.4.1 Developer documentation.	0..1	Required if custom API

4.6.4. DataCatalog attributes

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

4.6.5. Full example

A full dataset description that includes required and recommended attributes.

{
  "@context": "https://schema.org/",
  "@type": "Dataset",
  "@id": "http://data.bibliotheken.nl/id/dataset/rise-alba",
  "name": "Alba amicorum van de Koninklijke Bibliotheek",
  "description": "Alba amicorum van de Koninklijke Bibliotheek, een dataset gedefinieerd voor het Europeana Rise of Literacy project.",
  "license": "http://creativecommons.org/publicdomain/zero/1.0/",
  "dateCreated": "2019-04-14",
  "datePublished": "2019-05-21",
  "dateModified": "2019-08-15",
  "keywords": [
    "alba amicorum"
  ],
  "includedInDataCatalog": "http://data.bibliotheken.nl/id/datacatalog",
  "inLanguage": [
    "nl-NL",
    "en-US"
  ],
  "mainEntityOfPage": "https://www.kb.nl/bronnen-zoekwijzers/kb-collecties/moderne-handschriften-vanaf-ca-1550/alba-amicorum",
  "publisher": {
    "@type": "Organization",
    "@id": "https://www.kb.nl",
    "name": "Koninklijke Bibliotheek",
    "alternateName": "KB",
    "sameAs": "https://ror.org/02w4jbg70"
  },
  "creator": {
    "@type": "Organization",
    "@id": "https://www.kb.nl",
    "name": "Koninklijke Bibliotheek",
    "alternateName": "KB",
    "sameAs": "https://ror.org/02w4jbg70"
  },
  "distribution": [
    {
      "@type": "DataDownload",
      "encodingFormat": "application/sparql-query",
      "contentUrl": "http://data.bibliotheken.nl/sparql"
    },
    {
      "@type": "DataDownload",
      "encodingFormat": "text/turtle",
      "contentUrl": "http://data.bibliotheken.nl/files/alba_20201016.ttl.gz",
      "name": "Datadump Alba Amicorum",
      "datePublished": "2019-05-21",
      "dateModified": "2019-08-15",
      "contentSize": "614K"
    }
  ]
}

5. Tools