It is as much hidden metadata as is any other of such attempts, like schema.org and what else exists. It is a not so beautiful repetition of stuff that is already in the html, true, but it stems from another way of thinking about metadata. Maybe the RDF community does not like it anymore, but it was a thing.<p>Note that I&#x27;m not fan of this, rel=trackback is what should be used. But it is not complicated to add those tags into a page, which was my point.<p>The DRY principle in its original form does not apply here: The information in those tags will change when the information in the database changes. They are not hardcoded.