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>