Aside from a spec that tells the "how", I don't understand what or why it is. What problem does this solve? How can or should I use this?
For privacy preserving IDs I suggest you look at Coconut Credentials — https://medium.com/chainspace/coconut-threshold-issuance-sel...
I find the choice to use ownership language strange. The url/uri based systems are fundamentally inadequate for many if not most of their current use cases (they are not and never were intended to be persistent), and as the authors point out, there the urn system requires a central authority. Thus there is a need for some other system.
The ability to claim and prove authorship and determine the provenance (or tampering) of an identified document is crucial. For the most part people bindly trust that the nytimes.com that they are seeing is the real one, but there are so many ways that the can be compromised it is hard to comprehend.
More importantly, the current ways of protecting oneself against such issues are no longer accessible to the common man except via an interaction with some giant corporate edifice that they also have to trust. If you want to publish a document and distribute it in a way that its integrity and authorship can be determined there aren't good options.
Even more more to the point, there is currently no way general way to give a link to such a document that can be dereferenced to an untrusted host in such a way that the integrity of the document can be verified.
I supposed we could all share magnet links and check that they were signed with the nytimes pgp key, but then we are back to the issue of how to determine and distribute the nytimes pgp key. The WOT doesn't work, and pgp fails for anonymous publishing. Maybe the infrastructure behind DIDs will be able to solve the problems with WOT.
It will be interesting to see what comes of this, but I'm wary of its adjacency to the blockchain buzzwords.
See also:
https://en.wikipedia.org/wiki/Self-sovereign_identity
https://identity.foundation/
https://human-id.org/ (a non-profit startup)