Digital Content
Introduction
It is very unlikely that the descriptions provided in the Linked Art model are the only digital representations of the entities that they describe. There are also digital images, web pages, and other related content that should be referenced from the descriptions of the entities. The digital object may be also be the entity of interest, such as an eBook, net art, or a digital installation with its own separate record. This section describes how to describe and link digital resources in the Linked Art model.
Digital objects are generally treated in the same way as physical objects -- they are carriers of information, not the information itself. The information is described by a work that is then digitally carried or shown by the digital object. This ensures that a digital facsimile and the physical object itself are both related to the same information. For example, a PDF (a DigitalObject) and a printed copy (a HumanMadeObject) of that PDF both carry exactly the same textual content (a LinguisticObject).
Core Digital Object Properties
All Digital Objects share some basic characteristics, regardless of their particular nature. The basic patterns of Name, Identifier, Classification, and Statement all apply in the regular way. Beyond the baseline, digital objects can have the following descriptive features:
- Access Point - The URLs where the actual file itself is available. The URL is given the
typeofDigitalObjectfor consistency, but the URL is the important aspect. For example, the access point for an image would be the URL from which you get the actual pixels, rather than a linked data description of the image. - Format - The
formatof a digital object is its media type, often called a MIME type, given as a string. - Standard - Many digital objects further conform to standard specifications, which can be referenced using the
conforms_toproperty. This differs fromformat, as there may not be a media type for the specification, and fromclassified_aswhich is a broader classification (Image, rather than conforming to the standard for JPEG 2000) - Dimensions - Digital dimensions follow the same pattern as physical dimensions, but might use different types (file size) or the same (height, width for images) and different units (bytes, pixels).
- Creation - Digital Objects are created by
Creationevents rather thanProductionevents, but otherwise have the same activity model.
This allows us to consistently and coherently model both physical and digital information carriers as core items of interest. In particular, a digital image file digitally_shows a VisualItem, or digitally_carries a LinguisticObject.
Deletion / Erasure
It is currently not possible within the model to delete or erase a digital object. This will be added in a future minor version, and can be discussed in the github issue
Example:
The Rijksmuseum published a digital publication on the web about their conservation efforts for The Night Watch.
{
"@context": "https://linked.art/ns/v1/linked-art.json",
"id": "https://linked.art/example/digital/operation_nw/1",
"type": "DigitalObject",
"_label": "Operation Night Watch Publication",
"classified_as": [
{
"id": "http://vocab.getty.edu/aat/300264578",
"type": "Type",
"_label": "Web Page"
}
],
"identified_by": [
{
"type": "Name",
"content": "Operation Night Watch"
}
],
"dimension": [
{
"type": "Dimension",
"_label": "220 kb",
"classified_as": [
{
"id": "http://vocab.getty.edu/aat/300265863",
"type": "Type",
"_label": "File Size"
}
],
"value": 220,
"unit": {
"id": "http://vocab.getty.edu/aat/300265870",
"type": "MeasurementUnit",
"_label": "kilobytes"
}
}
],
"access_point": [
{
"id": "https://www.rijksmuseum.nl/en/stories/operation-night-watch",
"type": "DigitalObject"
}
],
"format": "text/html",
"conforms_to": [
{
"id": "http://w3.org/TR/html",
"type": "InformationObject"
}
],
"created_by": {
"type": "Creation",
"timespan": {
"type": "TimeSpan",
"begin_of_the_begin": "2019-07-19T00:00:00Z",
"end_of_the_end": "2019-07-21T00:00:00Z"
},
"carried_out_by": [
{
"id": "https://linked.art/example/group/rijksmuseum",
"type": "Group",
"_label": "Rijksmuseum"
}
]
},
"digitally_carries": [
{
"id": "https://linked.art/example/text/operation_nw_en",
"type": "LinguisticObject",
"_label": "Operation Night Watch in English"
}
]
}
Digital Surrogates
Some digital representations are intended to be faithful reproductions of a physical object. Especially when digitizing two dimensional works, it is useful to distinguish between a digital image that depicts the object generally, but perhaps along with other objects, people and the surroundings, compared to a digital image which shows only the same visual content as the physical object. We can be more explicit that the physical object shows the same intellectual content that the digital image digitally_shows.
These images are sometimes called "Digital Surrogates", as they can stand in for the physical object. A digital surrogate might show more than just the object, such as a color strip and a ruler, however the main focus of the visual item must clearly be the object itself. The line between surrogate and depiction is left to the policies and practices of implementing organizations.
Example:
The same visual item is shown by both the physical painting, and the digitized image of the painting.
{
"@context": "https://linked.art/ns/v1/linked-art.json",
"id": "https://linked.art/example/object/spring/8",
"type": "HumanMadeObject",
"_label": "Jeanne (Spring) by Manet",
"identified_by": [
{
"type": "Name",
"content": "Jeanne (Spring)"
}
],
"shows": [
{
"id": "https://linked.art/example/visual/spring",
"type": "VisualItem",
"_label": "Visual Content of Spring"
}
]
}
{
"@context": "https://linked.art/ns/v1/linked-art.json",
"id": "https://linked.art/example/digital/spring/1",
"type": "DigitalObject",
"_label": "Jeanne (Spring) (Digital)",
"identified_by": [
{
"type": "Name",
"content": "Jeanne (Spring)"
}
],
"digitally_shows": [
{
"id": "https://linked.art/example/visual/spring",
"type": "VisualItem",
"_label": "Visual Content of Spring"
}
]
}
References to Digital Content
Digital Images
Many of the entities that are described using Linked Art will have digital images that depict them. These images are useful for building compelling user interfaces for the data, and often take a prominent position in those interfaces. However these images might not be main entity of interest, merely a representation of the entity being described. If this is the case, then the Digital Object is only meaningful within the documentation relative to the main entity, and it is thus both acceptable and more convenient to embed the description of the image within the main entity's record. The pattern is designed to facilitate showing the image in a user interface, and as such only a few core properties should be used.
Example:
Rembrandt is depicted in a digital image hosted at wikimedia.
{
"@context": "https://linked.art/ns/v1/linked-art.json",
"id": "https://linked.art/example/person/rembrandt/15",
"type": "Person",
"_label": "Rembrandt",
"representation": [
{
"type": "VisualItem",
"digitally_shown_by": [
{
"type": "DigitalObject",
"_label": "Image of Rembrandt",
"classified_as": [
{
"id": "http://vocab.getty.edu/aat/300215302",
"type": "Type",
"_label": "Digital Image"
}
],
"format": "image/jpeg",
"access_point": [
{
"id": "https://upload.wikimedia.org/wikipedia/commons/b/bd/Rembrandt_van_Rijn_-_Self-Portrait_-_Google_Art_Project.jpg",
"type": "DigitalObject"
}
]
}
]
}
]
}
Web Pages
Another very common scenario is that there is a web page about the object, perhaps managed by a collections management system. For humans, this page is much more useful than the data intended for machines. It can be referenced with the subject_of property, and points to a DigitalObject which is classified_as a web page, or aat:300264578. The home page can have a format of "text/html" and other properties.
Example:
There is a home page for Jeanne in the Getty collections.
{
"@context": "https://linked.art/ns/v1/linked-art.json",
"id": "https://linked.art/example/object/spring/9",
"type": "HumanMadeObject",
"_label": "Jeanne (Spring) by Manet",
"classified_as": [
{
"id": "http://vocab.getty.edu/aat/300033618",
"type": "Type",
"_label": "Painting",
"classified_as": [
{
"id": "http://vocab.getty.edu/aat/300435443",
"type": "Type",
"_label": "Type of Work"
}
]
}
],
"identified_by": [
{
"type": "Name",
"content": "Jeanne (Spring)"
}
],
"subject_of": [
{
"type": "LinguisticObject",
"digitally_carried_by": [
{
"type": "DigitalObject",
"classified_as": [
{
"id": "http://vocab.getty.edu/aat/300264578",
"type": "Type",
"_label": "Web Page"
}
],
"format": "text/html",
"access_point": [
{
"id": "https://www.getty.edu/art/collection/object/103QTZ",
"type": "DigitalObject"
}
]
}
]
}
]
}
IIIF Manifests
IIIF, the International Image Interoperability Framework, is a very common way to make images and descriptions intended to be displayed to humans available. There are two primary alignments with the Digital Object model - Manifests from the IIIF Presentation API, and Images from the IIIF Image API.
The IIIF Presentation API manifest is considered to be a DigitalObject that is about the object, in the same way as the home page of the object in a collection information system. There is linguistic content within the manifest, that could be have one or more languages associated with it, and thus we have the same intermediary LinguisticObject as the value of the subject_of property. The conformsTo property of the Digital Object should be used to refer to the top level URI for the API: http://iiif.io/api/presentation/
And per that specification, the media type to be used in format follows the pattern: application/ld+json;profile="http://iiif.io/api/presentation/3/context.json"
The major version is present in the media type, allowing a consumer to distinguish which to use if multiple versions are simultaneously available.
Example:
Jeanne has a IIIF Presentation API Manifest.
{
"@context": "https://linked.art/ns/v1/linked-art.json",
"id": "https://linked.art/example/object/spring/10",
"type": "HumanMadeObject",
"_label": "Jeanne (Spring) by Manet",
"classified_as": [
{
"id": "http://vocab.getty.edu/aat/300033618",
"type": "Type",
"_label": "Painting",
"classified_as": [
{
"id": "http://vocab.getty.edu/aat/300435443",
"type": "Type",
"_label": "Type of Work"
}
]
}
],
"identified_by": [
{
"type": "Name",
"content": "Jeanne (Spring)"
}
],
"subject_of": [
{
"type": "LinguisticObject",
"digitally_carried_by": [
{
"type": "DigitalObject",
"access_point": [
{
"id": "https://media.getty.edu/iiif/manifest/db379bba-801c-4650-bc31-3ff2f712eb21",
"type": "DigitalObject"
}
],
"conforms_to": [
{
"id": "http://iiif.io/api/presentation/",
"type": "InformationObject"
}
],
"format": "application/ld+json;profile='http://iiif.io/api/presentation/3/context.json'"
}
]
}
]
}
IIIF Images
The IIIF Image API is a DigitalService from which various derivatives of the image content can be requested. This service is referenced via the digitally_available_via property from the DigitalObject that represents the digital image. The same image might have both access points and image services. This pattern is available for both images that are embedded representations, and images that have their own records.
The IIIF Image service, rather than the image itself, should have a conforms_to property that refers to "http://iiif.io/api/image/" as the URI of the InformationObject, so that applications know what sort of service is being referred to. The format property refers to the image information document (info.json) which has the media type of application/ld+json;profile="http://iiif.io/api/image/3/context.json"
Example:
The image of Jeanne is also available via a IIIF Image API service.
{
"@context": "https://linked.art/ns/v1/linked-art.json",
"id": "https://linked.art/example/object/spring/11",
"type": "HumanMadeObject",
"_label": "Jeanne (Spring) by Manet",
"classified_as": [
{
"id": "http://vocab.getty.edu/aat/300033618",
"type": "Type",
"_label": "Painting",
"classified_as": [
{
"id": "http://vocab.getty.edu/aat/300435443",
"type": "Type",
"_label": "Type of Work"
}
]
}
],
"identified_by": [
{
"type": "Name",
"content": "Jeanne (Spring)"
}
],
"representation": [
{
"type": "VisualItem",
"digitally_shown_by": [
{
"type": "DigitalObject",
"classified_as": [
{
"id": "http://vocab.getty.edu/aat/300215302",
"type": "Type",
"_label": "Digital Image"
}
],
"access_point": [
{
"id": "https://media.getty.edu/iiif/image/8094f61e-e458-42bd-90cf-a0ed0dcc90b9/full/full/0/default.jpg",
"type": "DigitalObject"
}
],
"digitally_available_via": [
{
"type": "DigitalService",
"access_point": [
{
"id": "https://media.getty.edu/iiif/image/8094f61e-e458-42bd-90cf-a0ed0dcc90b9",
"type": "DigitalObject"
}
],
"conforms_to": [
{
"id": "http://iiif.io/api/image",
"type": "InformationObject"
}
],
"format": "application/ld+json;profile='http://iiif.io/api/image/3/context.json'"
}
]
}
]
}
]
}
