All columns (variables): Two possibilities, depending on whether we want data to be repeated or not.
Not-repeated (with exception of primary/foreign key): rf_id, next_transaction (also rf_id), num_conveyance (number in order of conveyance by date), acknowledgment_date (in ASSIGNOR for the assignment data paper but would be moved here. Could originally be stored in ASSIGNOR until CONVEYANCE is generated), execution_date (same deal as acknowledgment date, should probably be moved here; if there are multiple execution dates, we will store the last one) conveyance_type
Repeated, also include: assignee, assignor, patent_id
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