schema:             DNS-SCHEMA
ref:                nx3.domain
dir-name:           dns
key:                domain     required   single    primary schema
key:                nserver    required   multiple  > [domain-name] [ip-addr]
key:                descr      optional   single
key:                mnt-by     required   multiple  lookup=nx3.mntner
key:                admin-c    optional   multiple  lookup=nx3.person,nx3.role
key:                tech-c     optional   multiple  lookup=nx3.person,nx3.role
key:                org        optional   multiple  lookup=nx3.organisation
key:                country    optional   single
key:                ds-rdata   optional   multiple
key:                remarks    optional   multiple
key:                source     required   single    lookup=nx3.registry
mnt-by:             NX3-MNT
source:             NX3