Hello!

I am trying to develop a modest extension that would be useful for users, consumers, and publishers, of information related to the field of law. In doing this, Protégé has been my editor of choice.

I have added schema: as a prefix and have been using said prefix in creating subclasses of schema:CreativeWork and others. But as I was reviewing the GS1 external extension ontology file, I noticed that, for some of their classes, they use skos:exactMatch to make an association. For instance, GS1's Brand class is annotated as a skos:exactMatch for http://schema.org/Brand. However, GS1 uses the schema: prefix for other classes, such as schema:Product.

As far as I can tell, the only difference between these two usages is whether the class is used at the same hierarchy level.

Specifically, Schema.org's Brand class is nested as a subclass of Intangible, which is itself a subclass of Thing. GS1, however, only nests Brand as a subclass of Thing and does not have an Intangible subclass of Thing.

Conversely, GS1's schema:Product class is nested the same as Schema.org's Product class, i.e., as a subclass of Thing.

If my proposal turns into a proposed external extension, am I correct that:

1. skos:exactMatch is appropriate when a vocabulary utilizes a Schema.org class or property, but utilizes it at a different level of hierarchy than Schema.org; and

2. The schema: prefix is appropriate when a vocabulary utilizes a Schema.org class or property at the same level of hierarchy as Schema.org?

If I am not correct, then what is the difference between using the schema: prefix and the skos:exactMatch annotation?