Web Identity


Linking classes, concepts, and individuals

Friday, October 3rd, 2008 4:59 pm

A question that keeps arising is why define a new URI for existing OWL classes, SKOS concepts, or existing named entities?

The answer is to provide a way to link classes, concepts, and individuals across ontologies with an idea rooted in the human mind.

Take, for example, organic food. The idea is known to exist in the human mind because it exists as a linguistic concept, i.e. you can see signs for it at the grocery store. However, depending on your needs, you might represent this idea very differently in an ontology.

A food industry ontology might make food:Organic and food:NonOrganic subclasses of food:Food to help reason about the nature of specific items. The publication industry might make a SKOS concept topic:OrganicFood to categorize it’s articles. A company database might consider making organic food an instance of a Product class:

ex:ExampleFarms ex:produces product:OrganicFood

Each concept has a specific representation in it’s ontology with it’s own URI. Declaring these as similar with owl:sameAs would confuse a logical reasoner trying to instantiate the objects.

However, there is still a benefit to linking these concepts across the semantic web. A search engine could easily find related resources, and a reasoner could instantiate each with local semantics depending on it’s linguistic context…and still know facts about it in the others.

The oguid:identical property provides this loose linkage and the Open GUID URI provides a common referent as the concept perceived by humans.  Paraphrased:

<food:Organic> oguid:identical <oguid:OrganicFood>
<topic:OrganicFood> oguid:identical <oguid:OrganicFood>
<product:OrganicFood> oguid:identical <oguid:OrganicFood>

2 Responses to “Linking classes, concepts, and individuals”

  • Bernard Says:

    Two remarks on this example.

    Why do you write oguid:OrganicFood instead of the actual URI
    This does not seem consistent about what you write everywhere else about the necessary “opacity” and “ugliness” of oguid URIs.

    Using so-called “multilingual” URIs such as “bar:LabelAB” or “foo:AlimentosOrganicos” would help to make the point.


  • Jason Says:

    I was just paraphrasing so the triple would fit on one line…probably not a good enough reason to be inconsistent. Since this post was meant to be read by humans, it seemed safe to use a short hand. An actual RDF document would look more like this.

    I actually kind of like the result. I am looking for ways to embed references to Open GUIDs in content in a manner that is usable and resolvable. Using an href seems like a good start…though a float over div with the keywords and description would be better. Hopefully tools will get to the point that we have the best of both worlds.

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