Digital Integration - Linked Art

Table of Contents

Introduction
Core Digital Objects
- Digital Surrogates
References to 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. It is very likely that there are 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. 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 Objects

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 type of DigitalObject for 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 format of 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_to property. This differs from format, as there may not be a media type for the specification, and from classified_as which 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 Creation events rather than Production events, 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.

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"
    }
  ]
}

graph TD classDef object stroke:black,fill:#E1BA9C,rx:20px,ry:20px; classDef actor stroke:black,fill:#FFBDCA,rx:20px,ry:20px; classDef type stroke:red,fill:#FAB565,rx:20px,ry:20px; classDef name stroke:orange,fill:#FEF3BA,rx:20px,ry:20px; classDef dims stroke:black,fill:#c6c6c6,rx:20px,ry:20px; classDef infoobj stroke:#907010,fill:#fffa40,rx:20px,ry:20px classDef timespan stroke:blue,fill:#ddfffe,rx:20px,ry:20px classDef place stroke:#3a7a3a,fill:#aff090,rx:20px,ry:20px classDef event stroke:#1010FF,fill:#96e0f6,rx:20px,ry:20px classDef literal stroke:black,fill:#f0f0e0; classDef classstyle stroke:black,fill:white; O1(digital/operation_nw/1) class O1 digital; O1-- type -->O1_0[DigitalObject] class O1_0 classstyle; O1-- _label -->O1_4("''Operation Night Watch Publication''") class O1_4 literal; O2(aat:300264578) class O2 type; O2-- type -->O2_0[Type] class O2_0 classstyle; O2-- _label -->O2_3("''Web Page''") class O2_3 literal; O1-- classified_as -->O2 O3( _ ) class O3 name; O3-- type -->O3_0[Name] class O3_0 classstyle; O3-- content -->O3_2("''Operation Night Watch''") class O3_2 literal; O1-- identified_by -->O3 O4( _ ) class O4 dims; O4-- type -->O4_0[Dimension] class O4_0 classstyle; O4-- _label -->O4_2("''220 kb''") class O4_2 literal; O5(aat:300265863) class O5 type; O5-- type -->O5_0[Type] class O5_0 classstyle; O5-- _label -->O5_3("''File Size''") class O5_3 literal; O4-- classified_as -->O5 O4-- value -->O4_4(220) class O4_4 literal; O6(aat:300265870) class O6 type; O6-- type -->O6_0[MeasurementUnit] class O6_0 classstyle; O6-- _label -->O6_3("''kilobytes''") class O6_3 literal; O4-- unit -->O6 O1-- dimension -->O4 O7(https://www.rijksmuseum.nl/en/stories/operation-night-watch) class O7 digital; O7-- type -->O7_0[DigitalObject] class O7_0 classstyle; O1-- access_point -->O7 O1-- format -->O1_9("''text/html''") class O1_9 literal; O8(http://w3.org/TR/html) class O8 infoobj; O8-- type -->O8_0[InformationObject] class O8_0 classstyle; O1-- conforms_to -->O8 O9( _ ) class O9 event; O9-- type -->O9_0[Creation] class O9_0 classstyle; O10( _ ) class O10 timespan; O10-- type -->O10_0[TimeSpan] class O10_0 classstyle; O10-- begin_of_the_begin -->O10_2("''2019-07-19T00:00:00Z''") class O10_2 literal; O10-- end_of_the_end -->O10_3("''2019-07-21T00:00:00Z''") class O10_3 literal; O9-- timespan -->O10 O11(group/rijksmuseum) class O11 actor; O11-- type -->O11_0[Group] class O11_0 classstyle; O11-- _label -->O11_3("''Rijksmuseum''") class O11_3 literal; O9-- carried_out_by -->O11 O1-- created_by -->O9 O12(text/operation_nw_en) class O12 infoobj; O12-- type -->O12_0[LinguisticObject] class O12_0 classstyle; O12-- _label -->O12_3("''Operation Night Watch in English''") class O12_3 literal; O1-- digitally_carries -->O12

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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 the 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"
    }
  ]
}

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{
  "@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"
    }
  ]
}

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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 are often not the main items of interest for the data, merely representations of the entities.

One image might show many different entities, of different types. An image of an artist standing next to one of her paintings would show both the artist (a Person) and the painting (a HumanMadeObject). Further, the same image might be shown by many digital copies and derivatives, each available at a different URL. The same image might also be shown by a physical object, either by printing a digital file or that the digital image is a digitization of the physical object.

Note that this usage does not require a separate record to manage the digital object, instead the pattern is inverted with only a smaller set of properties available.

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"
            }
          ]
        }
      ]
    }
  ]
}

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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. As with digital images, 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"
            }
          ]
        }
      ]
    }
  ]
}

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IIIF Manifests

IIIF, the International Image Interoperability Framework, is an increasingly 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 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 should be used to refer to the context document for the API to ensure it can be recognized, including which version.

The specification that a Manifest conforms to is the Presentation 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"

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'"
        }
      ]
    }
  ]
}

graph TD classDef object stroke:black,fill:#E1BA9C,rx:20px,ry:20px; classDef actor stroke:black,fill:#FFBDCA,rx:20px,ry:20px; classDef type stroke:red,fill:#FAB565,rx:20px,ry:20px; classDef name stroke:orange,fill:#FEF3BA,rx:20px,ry:20px; classDef dims stroke:black,fill:#c6c6c6,rx:20px,ry:20px; classDef infoobj stroke:#907010,fill:#fffa40,rx:20px,ry:20px classDef timespan stroke:blue,fill:#ddfffe,rx:20px,ry:20px classDef place stroke:#3a7a3a,fill:#aff090,rx:20px,ry:20px classDef event stroke:#1010FF,fill:#96e0f6,rx:20px,ry:20px classDef literal stroke:black,fill:#f0f0e0; classDef classstyle stroke:black,fill:white; O1(object/spring/10) class O1 object; O1-- type -->O1_0[HumanMadeObject] class O1_0 classstyle; O1-- _label -->O1_4("''Jeanne (Spring) by Manet''") class O1_4 literal; O2(aat:300033618) class O2 type; O2-- type -->O2_0[Type] class O2_0 classstyle; O2-- _label -->O2_3("''Painting''") class O2_3 literal; O3(aat:300435443) class O3 type; O3-- type -->O3_0[Type] class O3_0 classstyle; O3-- _label -->O3_3("''Type of Work''") class O3_3 literal; O2-- classified_as -->O3 O1-- classified_as -->O2 O4( _ ) class O4 name; O4-- type -->O4_0[Name] class O4_0 classstyle; O4-- content -->O4_2("''Jeanne (Spring)''") class O4_2 literal; O1-- identified_by -->O4 O5( _ ) class O5 infoobj; O5-- type -->O5_0[LinguisticObject] class O5_0 classstyle; O6( _ ) class O6 digital; O6-- type -->O6_0[DigitalObject] class O6_0 classstyle; O7(https://media.getty.edu/iiif/manifest/db379bba-801c-4650-bc31-3ff2f712eb21) class O7 digital; O7-- type -->O7_0[DigitalObject] class O7_0 classstyle; O6-- access_point -->O7 O8(http://iiif.io/api/presentation/) class O8 infoobj; O8-- type -->O8_0[InformationObject] class O8_0 classstyle; O6-- conforms_to -->O8 O6-- format -->O6_4("''application/ld+json;profile='http://iiif.io/api/presentation/3/context.json'''") class O6_4 literal; O5-- digitally_carried_by -->O6 O1-- subject_of -->O5

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IIIF Images

The IIIF Image API is a DigitalService from which various derivatives of the image content can be requested. Similarly to the access_point property used in the previous sections, this service is referenced via the digitally_available_via property from the core DigitalObject that represents the digital image. The same image might have both access points and image services.

The IIIF Image service should have a conforms_to property that refers to "http://iiif.io/api/image/" as the URI of an 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'"
            }
          ]
        }
      ]
    }
  ]
}

graph TD classDef object stroke:black,fill:#E1BA9C,rx:20px,ry:20px; classDef actor stroke:black,fill:#FFBDCA,rx:20px,ry:20px; classDef type stroke:red,fill:#FAB565,rx:20px,ry:20px; classDef name stroke:orange,fill:#FEF3BA,rx:20px,ry:20px; classDef dims stroke:black,fill:#c6c6c6,rx:20px,ry:20px; classDef infoobj stroke:#907010,fill:#fffa40,rx:20px,ry:20px classDef timespan stroke:blue,fill:#ddfffe,rx:20px,ry:20px classDef place stroke:#3a7a3a,fill:#aff090,rx:20px,ry:20px classDef event stroke:#1010FF,fill:#96e0f6,rx:20px,ry:20px classDef literal stroke:black,fill:#f0f0e0; classDef classstyle stroke:black,fill:white; O1(object/spring/11) class O1 object; O1-- type -->O1_0[HumanMadeObject] class O1_0 classstyle; O1-- _label -->O1_4("''Jeanne (Spring) by Manet''") class O1_4 literal; O2(aat:300033618) class O2 type; O2-- type -->O2_0[Type] class O2_0 classstyle; O2-- _label -->O2_3("''Painting''") class O2_3 literal; O3(aat:300435443) class O3 type; O3-- type -->O3_0[Type] class O3_0 classstyle; O3-- _label -->O3_3("''Type of Work''") class O3_3 literal; O2-- classified_as -->O3 O1-- classified_as -->O2 O4( _ ) class O4 name; O4-- type -->O4_0[Name] class O4_0 classstyle; O4-- content -->O4_2("''Jeanne (Spring)''") class O4_2 literal; O1-- identified_by -->O4 O5( _ ) class O5 infoobj; O5-- type -->O5_0[VisualItem] class O5_0 classstyle; O6( _ ) class O6 digital; O6-- type -->O6_0[DigitalObject] class O6_0 classstyle; O7(aat:300215302) class O7 type; O7-- type -->O7_0[Type] class O7_0 classstyle; O7-- _label -->O7_3("''Digital Image''") class O7_3 literal; O6-- classified_as -->O7 O8(https://media.getty.edu/iiif/image/8094f61e-e458-42bd-90cf-a0ed0dcc90b9/full/full/0/default.jpg) class O8 digital; O8-- type -->O8_0[DigitalObject] class O8_0 classstyle; O6-- access_point -->O8 O9( _ ) class O9 digital; O9-- type -->O9_0[DigitalService] class O9_0 classstyle; O10(https://media.getty.edu/iiif/image/8094f61e-e458-42bd-90cf-a0ed0dcc90b9) class O10 digital; O10-- type -->O10_0[DigitalObject] class O10_0 classstyle; O9-- access_point -->O10 O11(http://iiif.io/api/image) class O11 infoobj; O11-- type -->O11_0[InformationObject] class O11_0 classstyle; O9-- conforms_to -->O11 O9-- format -->O9_4("''application/ld+json;profile='http://iiif.io/api/image/3/context.json'''") class O9_4 literal; O6-- digitally_available_via -->O9 O5-- digitally_shown_by -->O6 O1-- representation -->O5

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