aut-num:       [mandatory]  [single]     [primary/look-up key]
as-name:       [mandatory]  [single]     [ ]
descr:         [mandatory]  [multiple]   [ ]
country:       [mandatory]  [single]     [ ]
member-of:     [optional]   [multiple]   [ ]
import:        [optional]   [multiple]   [ ]
export:        [optional]   [multiple]   [ ]
default:       [optional]   [multiple]   [ ]
remarks:       [optional]   [multiple]   [ ]
admin-c:       [mandatory]  [multiple]   [inverse key]
tech-c:        [mandatory]  [multiple]   [inverse key]
cross-mnt:     [optional]   [multiple]   [inverse key]
cross-nfy:     [optional]   [multiple]   [inverse key]
notify:        [optional]   [multiple]   [inverse key]
mnt-lower:     [optional]   [multiple]   [inverse key]
mnt-routes:    [optional]   [multiple]   [inverse key]
mnt-by:        [mandatory]  [multiple]   [inverse key]
changed:       [mandatory]  [multiple]   [ ]
source:        [mandatory]  [single]     [ ]