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Vocabulary Patterns

Scope

This content is in intended to convey Best Practice patterns in vocabulary content

Audience

Technical vocabulary creators.

All the patterns documented here assume the use of the SKOS data model for vocabulary content and Semantic Web methods for data management and access.

Outcome

Technical vocabulary creators should learn both what KurrawongAI considers to be Best Practice for certain aspects of vocabulary content and also how KurrawongAI and other vocabulary creation and publication tools support the pattern.

Images

Can we use images for concepts in vocabularies?

Context

Some vocabularies lend themselves to the use of images to either define or explain the concepts they contain. For example, a vocabulary about road signs really should show images of the sign, not just describe them. Other vocabularies might like to exemplify concepts with images.

Solution

Yes we can use images with the following clarifications:

  1. there is more than one way
  2. different approaches require different system capabilities for authoring or displaying vocabs

Conceptual handling

Conceptually, we just link an image to a Concept within a vocab using an appropriate predicate. The SKOS Reference document's Notes section indicates that certain note predicates such as skos:example might be appropriate since the don't only have to be used with text, even though they usually are.

Note

If a Concept is actually defined by an image, it may seem appropriate to link directly to the image using the skos:definition predicated but we advise against this as it may be invalid for certain vocabulary profiles such as VocPub and may be hard for systems to implement. Instead use another predicate and describe how the image, indicated by the chosen predicate, is the defining part of the Concept in the definition field, in text.

We can also choose to use a non-SKOS predicate, especially common ones used for images, such as schema:image. This would allow the use of regular SKOS predicates, such as skos:definition, skos:example etc. for their common use and the image predicate is an extra.

The information about the images actually linked to by skos:example or schema:image can be one of the following:

  • a web address - URL
    • e.g. https://upload.wikimedia.org/wikipedia/commons/4/4c/2019-07-29_172052_Rain_in_Berlin.jpg - a publicly available image on WikiMedia
  • a local file path
    • e.g. images/germany/rain_in_berlin.jpg - only available on a particular system
  • embedded image content
    • e.g. an SVG image defined in XML text
    • e.g. a hex-encoded raster image, like a JPG
  • a Blank Node describing an image

There are pros and cons to each type of information listed above.

A web address is easy to record - just a predicate like schema:image pointing to the URL - but it will break if the image disappears offline, so the vocabulary has a dependency on the image's stability to keep working.

A local file path will only work if any tool publishing the vocabulary can access and on-deliver (render) the image.

An embedded image stays within the vocab's source data file, which means it can't ever be lost, but could be large: the JPG image linked to in the web address bullet above is 7.5MB as a JPEG but 137MB when converted to HEX which is a form of text encoding that can be used in an RDF file. This may only be appropriate for small vector images such as icons of map symbols.

If we want to provide more information about the image than either just its embedded content or a link to its location, we can qualify it by linking to a Blank Node from which we can then link to remote content via a URL or local file path or to embedded content. From the same Blank Node, we can then also link to other information such as captions, copyright info, etc. See Examples below.

Examples

URL using schema:image

PREFIX schema: <https://schema.org/>
PREFIX skos: <http://www.w3.org/2004/02/skos/core#>
PREFIX xsd: <http://www.w3.org/2001/XMLSchema#>

:dog
  a skos:Concept ;
  skos:prefLabel "Dog"@en ;
  skos:altLabel "Domestic Dog"@en ;
  skos:definition "The dog (Canis familiaris or Canis lupus familiaris) is a domesticated descendant of the gray wolf."@en ;
  schema:image "https://en.wikipedia.org/wiki/Dog#/media/File:Chin_posing.jpg" ;
.

Note here the use of xsd:anyURI for a typed literal for the image link, as opposed to an IRI named node, which would be <https://en.wikipedia.org/wiki/Dog#/media/File:Chin_posing.jpg>. This is because the image is not part of the vocab's graph (the nodes in its data) but a link off to somewhere else.

Local file path using skos:example

PREFIX skos: <http://www.w3.org/2004/02/skos/core#>
PREFIX xsd: <http://www.w3.org/2001/XMLSchema#>

:dog
  a skos:Concept ;
  skos:prefLabel "Dog"@en ;
  skos:altLabel "Domestic Dog"@en ;
  skos:definition "The dog (Canis familiaris or Canis lupus familiaris) is a domesticated descendant of the gray wolf."@en ;
  skos:example "src/img/my_dog.jpg" ;
.

Embedded SVG image

PREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>
PREFIX skos: <http://www.w3.org/2004/02/skos/core#>
PREFIX xsd: <http://www.w3.org/2001/XMLSchema#>

:apron
    a skos:Concept ;
    skos:prefLabel "Apron"@en ;
    skos:definition "An apron, in geology, is a fan-like accumulation of sediments that spreads outward from the base of a slope, such as the edge of a continental shelf, a submarine mountain, or an island. It's typically formed by gravity-driven processes like submarine landslides, debris flows, or turbidity currents."@en  ;
    schema:image """<svg xmlns="http://www.w3.org/2000/svg" xmlns:inkscape="http://www.inkscape.org/namespaces/inkscape" xmlns:sodipodi="http://sodipodi.sourceforge.net/DTD/sodipodi-0.dtd" xmlns:svg="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" width="97.118958mm" height="74.286232mm" viewBox="0 0 97.118957 74.286232" version="1.1" id="svg5" xml:space="preserve" inkscape:version="1.2.2 (b0a8486, 2022-12-01)" sodipodi:docname="apron.inkscape.svg" inkscape:export-filename="apron.png" inkscape:export-xdpi="96" inkscape:export-ydpi="96"><sodipodi:namedview id="namedview7" pagecolor="#ffffff" bordercolor="#666666" borderopacity="1.0" inkscape:showpageshadow="2" inkscape:pageopacity="1" inkscape:pagecheckerboard="0" inkscape:deskcolor="#ffffff" inkscape:document-units="mm" showgrid="false" inkscape:zoom="1.8380915" inkscape:cx="75.077873" inkscape:cy="204.01596" inkscape:window-width="2063" inkscape:window-height="1210" inkscape:window-x="133" inkscape:window-y="70" 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id="layer1" style="display:inline" transform="translate(-53.17203,-43.635959)"><text xml:space="preserve" style="font-size:4.93889px;line-height:0.95;font-family:sans-serif;display:inline;stroke-width:0.264583" x="145.31673" y="68.72187" id="text364" inkscape:label="A'"><tspan sodipodi:role="line" id="tspan362" style="font-size:4.93889px;stroke-width:0.264583" x="145.31673" y="68.72187">A'</tspan></text><text xml:space="preserve" style="font-size:4.93889px;line-height:0.95;font-family:sans-serif;display:inline;stroke-width:0.264583" x="53.109329" y="69.1222" id="text356" inkscape:label="A"><tspan sodipodi:role="line" id="tspan354" style="font-size:4.93889px;stroke-width:0.264583" x="53.109329" y="69.1222">A</tspan></text><path style="fill:none;stroke:#0000ff;stroke-width:0.265;stroke-linecap:butt;stroke-linejoin:miter;stroke-dasharray:none;stroke-opacity:1" d="m 57.779747,66.186502 6.271707,0.13344 m 10.942123,-5.20418 c 3.257361,-3.824489 5.768834,-16.591931 11.876208,-17.347268 l 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style="fill:#0000ff;stroke:#0000ff;stroke-width:1.065;stroke-dasharray:none;paint-order:fill markers stroke;stop-color:#000000" id="path1209" cx="64.327316" cy="66.178802" rx="0.4272663" ry="0.37979227" inkscape:label="dot" /><ellipse style="fill:#0000ff;stroke:#0000ff;stroke-width:1.065;stroke-dasharray:none;paint-order:fill markers stroke;stop-color:#000000" id="path1209-8" cx="74.914024" cy="61.241501" rx="0.4272663" ry="0.37979227" inkscape:label="dot" /><ellipse style="fill:#0000ff;stroke:#0000ff;stroke-width:1.065;stroke-dasharray:none;paint-order:fill markers stroke;stop-color:#000000" id="path1209-6" cx="130.64854" cy="61.241505" rx="0.4272663" ry="0.37979227" inkscape:label="dot" /><ellipse style="display:inline;fill:#0000ff;stroke:#0000ff;stroke-width:1.065;stroke-dasharray:none;paint-order:fill markers stroke;stop-color:#000000" id="path1209-7" cx="140.61809" cy="66.463654" rx="0.4272663" ry="0.37979227" inkscape:label="dot" /></g><g inkscape:groupmode="layer" id="layer2" 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id="path1309" sodipodi:nodetypes="ccccccccccccc" /><path style="display:inline;fill:url(#linearGradient3524);fill-opacity:1;stroke:#0000ff;stroke-width:0.565;stroke-linecap:butt;stroke-linejoin:miter;stroke-dasharray:2.825;stroke-dashoffset:0;stroke-opacity:1" d="M 64.089946,105.39236 143.37158,88.301702" id="path1301" inkscape:label="line" /></g></svg>"""^^rdf:XMLLiteral ;
.

This example embeds the following simple image and yet the SVG literal used is large (long):

Note also that the literal value used for the SVG encoding of the image is XML, indicated using the rdf:XMLLiteral custom datatype.

Blank Node

Here an image at a local file path is given a caption and a copyright notice via a Blank Node of type schema:ImageObject using other schema.org predicates:

PREFIX skos: <http://www.w3.org/2004/02/skos/core#>
PREFIX xsd: <http://www.w3.org/2001/XMLSchema#>

:dog
  a skos:Concept ;
  skos:prefLabel "Dog"@en ;
  skos:altLabel "Domestic Dog"@en ;
  skos:definition "The dog (Canis familiaris or Canis lupus familiaris) is a domesticated descendant of the gray wolf."@en ;
  skos:example [
    a schema:ImageObject ;
    schema:contentLocation "src/img/my_dog.jpg" ;
    schema:caption "Fido, Nicholas' dog" ;
    schema:copyrightNotice "&copy; Nicholas Car, 2025" ;  
  ] ;
.

Discussion

There are several ways to associate images with Concepts in SKOS vocabularies and each have different pros and cons. Be sure to determine how your target vocabulary creation / management / publication systems handle images too.

Systems

The following is a list of KurrawongAI-supported vocabulary systems that have some image capability:

  • VocExcel
    • for the creation of vocabs
    • VocExcel v0.8.0, due for release in Jun, 2025, will contain an skos:example slot for Concepts that can be used to link to an image via URL
  • VocEdit
    • for the creation of vocabs
    • VocEdit already (May 2025) supports adding any predicated and literal values to Concepts, so the URL and local file path methods can be used now
    • the July 2025 release of VocEdit will support uploading small SVG files for the values of skos:example or schema:image predicates
  • Prez