Verifiable Data Registries

I’ve been going through the recent DID's Editor’s Draft and a question came to mind on what the characteristics of a Verifiable Data Registry are.  So, I started looking through the VC spec and Data Model and find similar language across all the different spec’s, data models,...

A role a system might perform by mediating the creation and verification <https://www.w3.org/TR/vc-data-model/#dfn-verify> of identifiers, keys, and other relevant data, such as verifiable credential <https://www.w3.org/TR/vc-data-model/#dfn-verifiable-credentials> schemas, revocation registries, issuer public keys, and so on, which might be required to use verifiable credentials <https://www.w3.org/TR/vc-data-model/#dfn-verifiable-credentials>. Some configurations might require correlatable identifiers for subjects <https://www.w3.org/TR/vc-data-model/#dfn-subjects>. Example verifiable data registries include trusted databases, decentralized databases, government ID databases, and distributed ledgers. Often there is more than one type of verifiable data registry utilized in an ecosystem.           

From: VC Data Model

The question that came to mind, is there a more definitive definition of what a Verifiable Data Registry is?  What characteristics must it have?  Usually, i have been equating it to a DLT, but I know that I have heard conversations indicating that it specifically was not restricted to this technology.

If someone could point me to any site or information that would be great!

Cheers!

Michael Shea.