route:         [mandatory]  [single]     [primary/look-up key]
descr:         [mandatory]  [multiple]   [ ]
country:       [optional]   [single]     [ ]
origin:        [mandatory]  [single]     [primary/inverse key]
holes:         [optional]   [multiple]   [ ]
member-of:     [optional]   [multiple]   [ ]
inject:        [optional]   [multiple]   [ ]
aggr-mtd:      [optional]   [single]     [ ]
aggr-bndry:    [optional]   [single]     [ ]
export-comps:  [optional]   [single]     [ ]
components:    [optional]   [single]     [ ]
remarks:       [optional]   [multiple]   [ ]
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]     [ ]