How are DIDs different from, the same as DOIs? (see https://www.doi.org/index.html)
Even though the language on the DOI site focuses on digital objects and DIDs are more general than that, I know that DOI proponents are discussing how they can be used as identifiers for anything.
Clearly, a DID could point to a DDO that contains the DOI for something.
Would it be possible to use a DOI as a key on the ledger?