Productontology URLs are 404 erroring, are there alternatives to denote new schema categories?

[RosemaryB]

Our team QA specialist recently noticing that the class identifier URLs via productontology are 404ing out saying that the "There is no Wikipedia article for (particular property)". They are even 404ing for productontology URLs that are examples on the productontology.com website!

Example:

http://www.productontology.org/id/Apple

The 404 page says that the wiki entry for "Apple" doesn't exist (lol)

Does anybody know what is going on with this website?  This service was extremely helpful for creating additionalType categories for schema categories that don't exist on schema.org.  Are there any alternatives to productontology now that these class identifier URLs are 404ing?

Thanks

[OVSEO]

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