Is using the Product Types Ontology with Schema.org still valid? 404 Errors

Question

You may have noticed my recent posts about Schema, as I am in the process of improving my local signals with search engines. If you haven't then don't worry here is just some of relevant Schema JSON-LD I'm using:

"@context": "http://schema.org",
"@type": "ProfessionalService",
"additionalType": "http://www.productontology.org/id/Web_design",
"name": "BYBE",

As you can see I'm using ProfessionalService with additionalType using The Product Types Ontology.

Since my local business is in the web design field I've opted to use:

• Using: http://www.productontology.org/id/Web_design
• From: https://en.wikipedia.org/wiki/Web_design

However visiting http://www.productontology.org/id/Web_design I receive a 404 page:

ERROR (404): No respective entry available

productontology.org cannot provide a class definition fo the requested URI.

Reason: There is no Wikipedia article http://en.wikipedia.org/wiki/Web_design for 'Web_design'.

If you want to use this word (to be precise: this "lemma") as a class, you must first create a respective article in the English Wikipedia by clicking on the link given above.

Here is the direct link to create such a page in Wikipedia: http://en.wikipedia.org/w/index.php?title=Web_design&action=edit.

productontology.org cannot provide a class definition for some names. This can have several reasons:

1. There is no English Wikipedia article for the requested name (lemma).
2. We cannot show the respective entry for legal reasons, e.g. because the requested name is a registered trademark.
3. We may also block certain lemmata if they are obviously unsuited as class names.

So the first thing I checked is if the page exists on Wikipedia and it does, so I thought maybe they don't support Web_design. So I visit their homepage and test their own examples and I'm surprised to find the same issue on everything.

Here is an example they list on the homepage:

• Soldering_iron
• http://www.productontology.org/id/Soldering_iron
• RDF/XML
• N3/Turtle
• HTML

Question(s):

• Should those URL's be returning valid pages?
• Should people avoid using The Product Types Ontology?

Answer 1

My guess is that productontology.org has some technical issues (according to someone that noticed the same, at least since 2016-08-04).

That should not stop you from using their URIs, though. Displaying information or providing data about the things the URIs represent is useful, but not formally required.

So the URI http://www.productontology.org/id/Web_design still represents the class "Web design", as it redirects with 303; no matter if the redirect target (which gives 404 currently) displays something useful, an error message, or nothing at all.

(I guess that productontology.org will fix this, so that information about the classes will again be displayed under /doc/.)

Update: Martin Hepp, who is responsible for productontology.org, took notice of the bug in 2016-07-14. The issue seems to stem from the "HTTP to HTTPS migration of the Wikipedia API". He also notes that it’s fine to use the URIs anyway.