schema:             NAMESPACE-SCHEMA
ref:                dn42.namespace
key:                namespace     required single   primary schema > [name]
key:                ns-schema     required single   > [schema]
key:                ns-owner      required single   > [schema]
key:                default-owner optional single   lookup=dn42.mntner  > [mntner]
key:                network-owner optional multiple > [parent-schema] [child-schema]
key:                primary-key   optional multiple > [schema] [primary]
mnt-by:             DN42-MNT
source:             DN42