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"All elements in the tables not marked as 'optional' are mandatory" ...
'OPTIONAL' is an RFC2119 keyword (used instead of 'MAY') for conformance clauses.
'mandatory' is not an RFC2119 keyword.
In tables 5-9, 5-10, 7-17, 10-26, 11-27 is 'optional' intended to specify
conformance or to indicate a cardinality/multiplicity ('0..x')?
Further confused by using the word 'optionally' in
Table 13-29 "A Sequence may optionally include a Lineage."
but 'Lineage' (Table 13-30) definition does not state it is 'optional'.