There are a number of netref object types that require unambiguous identifiers in order for the protocol to function properly. These include metadata elements, constraints, diagnostics, and schemas.The syntax would thus be:
info:netref/<netref object type>/<sub-authority>/<id>
example:
info:netref/metadata/1/question-id
For information about this NISO activity see:
http://www.niso.org/committees/committee_az.html
(Temporary note: this is analogous to the SRW info namespace.)