Provide an URL to a registered scheme that defines the globally-unique structure of the identifier(s) for your digital resource. Examples of identifier schemes include, but are not limited to URN, IRI, DOI, Handle, trustyURI, LSID, etc. Use the DOI for the identifier scheme specified in the FAIRSharing Registry (see https://fairsharing.org/standards/?q=&selected_facets=type_exact:identifier%20schema)
Rationale: The uniqueness of an identifier is a necessary condition to unambiguously refer that resource, and that resource alone. Otherwise, an identifier shared by multiple resources will confound efforts to describe that resource, or to use the identifier to retrieve it.